1. In his permanent impairment assessment report dated 18 June 2024, Dr Suyapto noted a request to assess permanent impairment from an injury to the left knee and associated surgical scarring and permanent impairment from an injury to the left hip and associated surgical scarring. He noted that both injuries were sustained on 7 February 2019. Dr Suyapto obtained a history including Ms Hanton's report of her symptoms at the time of the examination. He confirmed that the injuries to be assessed were stable in the sense that they had reached maximum medical improvement. He stated that there had been no changes to Ms Hanton's presentation in the three months leading to the examination and that it was unlikely her presentation would change in the foreseeable future.
2. He then proceeded to set out his reasoning, including the methodology utilised, for the permanent impairments that he assessed. He utilised chapter 3 of the Impairment Assessment Guidelines (IAG) and chapter 17 of the American Medical Association Guide to the Evaluation of Permanent Impairment (5th edition) (AMA 5). He stated, relevantly:

In relation to the hip, I have referenced table 17-34 of AMA 5. I have assigned moderate pain at 20 points given the reported pain score of 7 out of 10. Slight limp is assigned 8 points with no supportive device 11 points. Distance walks indoor assigned 2 points. She is not able to climb readily 1 point, difficulty putting shoes and socks on with 2 points, and sitting highchair 2 points. Unable to use public transport at 0 point. Given that there was no fixed adduction, fixed internal rotation, fixed external rotation, flexion contracture and leg length discrepancy less than 1.5 cm, each assigned 1 point and added to equal 5 points. The range of movement flexion of greater than 90° 1 point, abduction greater than 15° 1 point, adduction greater than 15° one point, external rotation of 30° is assigned 0 point and internal rotation greater than 15° 1 point. These are added to equal 4 points.

I have added all the points to equal 55 points. With reference to table 17-33, is assigned that fair result at 50% lower extremity impairment.

Given that the previous osteoarthritis in which the imaging in 2019 showed a 3 mm cartilage interval, a deduction of 7% lower extremity impairment will need to be applied with reference to table 17-31 of AMA 5. This results in 43% lower extremity impairment.

In relation to the left knee, I have referenced table 17-35. I have assigned severe pain at 0 point. The range of movement is 120° which is assigned 24 points. The AP stability of between 5-9 mm is assigned 5 points. Mediolateral of 5° is assigned 15 points. These are added to equal 44 points. The deduction includes extension lag of 10° which is assigned 10 points, and flexion contracture of 5° degrees is assigned 2 points. The 12 points is deducted from 44 equates to (sic) 32 points. This is assigned poor result at 75% lower extremity impairment.

I note in your report request you have outlined meniscectomy, however I was not able to find any operative note that says that she has had a meniscectomy. Noting that she has had a patellectomy which is assigned 22% lower extremity impairment, with reference to table 17-33. In relation to the arthritis, a 2 mm cartilage interval is assigned 20% lower extremity impairment with reference to table 17-31 of AMA 5. I have combined the impairment of patellectomy and arthritis, 22% with 20% which equates to 38% lower extremity impairment.

Still the quote I have deducted 38% from 75% to equal 37% lower extremity impairment.

Given the same date of injury, the lower extremity impairment of the left hip and left knee are combined, 43% with 37% to equal 64% lower extremity impairment. Using table 17-3, this is converted to 26% whole person impairment.

1. In relation to the surgical scarring, Dr Suyapto utilised table 13.1 of the IAG which is referred to as the TEMSKI scale. He allocated a 2% WPI from which he deducted 1% as a result of prior surgical scarring.
2. After combining the 1% WPI for scarring with the 26% WPI for impairment of function, Dr Suyapto concluded that the continued total impairment arising from the work injuries to the left hip and left knee, including surgical scarring, is a 27% WPI. At trial it was agreed that, by reference to the methodology utilised by Dr Suyapto, the overall assessment for the calculation of entitlement should be a 26% WPI.
3. Chapter 1.51 of the IAG provides that permanent impairment assessment reports are to be reviewed by the Corporation for compliance. In this case, the result of that review was a letter from the Corporation to Dr Suyapto raising for his consideration aspects of the content of his report. Dr Suyapto replied by supplementary report dated 25 July 2024. There was no change to his assessment of permanent impairment. The Corporation wrote again to Dr Suyapto by letter dated 30 July 2024. The trial book tendered in evidence does not contain a response by Dr Suyapto referring to that letter.
4. EML wrote to Dr Suyapto by letter dated 16 September 2024. Attached to that letter was a report of Dr Champion dated 26 August 2024. Dr Suyapto was asked to provide his opinion with respect to the assessment of permanent impairment in the light of the content of the report of Dr Champion.
5. Dr Suyapto provided a further report dated 1 October 2024. He referred to the report of Dr Champion and maintained his assessment of permanent impairment.
6. EML wrote again to Dr Suyapto by letter dated 26th November 2024. On this occasion, EML raised for Dr Suyapto's consideration, the correct construction and application of chapters 1.29 and 3.7 of the IAG. The methodology raised by EML is to combine the assessed presenting lower extremity impairment (LEI) of the left hip and left knee and then deduct the assessed pre-existing combined LEI of the left hip and left knee.[1] The resulting LEI is then converted to a WPI.[2] The methodology that had been adopted by Dr Suyapto was to assess the presenting left hip LEI, and deduct from it the pre-existing left hip LEI, assess the presenting left knee LEI, and deduct from it the pre-existing left knee lower extremity impairment, combine the remaining LEI and then convert from a LEI to a WPI. Dr Suyapto appears to have accepted the methodology raised by EML as an equally valid applicable method. He referred to chapter 1.38 of the IAG which states:
   • 1.38 The Guidelines and AMA 5 may specify more than one equally valid, applicable method that assessors can use to establish the degree of an injured person's permanent impairment. In that case, assessors should use the method(s) that results in the highest degree of permanent impairment.
7. Dr Suyapto maintained the methodology he utilised as being in accordance with the relevant medical guidelines and maintained his assessment of permanent impairment.
8. The practical significance of the methodology advanced by EML is that it would result in this case, in an overall assessment of 19% WPI in comparison to the methodology adopted by Dr Suyapto which, as already noted, results in an agreed 26% WPI. The parties have agreed that if the correct assessment is that of Dr Suyapto, then Ms Hanton is entitled to a lump sum of $89,306 pursuant to s 58 of the RTW Act and a further lump sum of $30,949.13 pursuant to s 56. The parties have also agreed that if the methodology advanced by EML is correct, then the combined WPI for the left knee and hip impairment and surgical scarring is 19% WPI. On that basis, the parties have agreed that Ms Hanton's entitlement pursuant to s 58 would be $46,229 and her entitlement pursuant to s 56 would be $15,968.15. The substantial difference is due, in part, to a non-linear increase in entitlement as the percentage of impairment increases.[3]

1. By letter dated 31 July 2024, EML determined that Ms Hanton is not entitled to any lump sum payment either pursuant to s 56 or s 58 of the RTW Act. The decision maker stated that the assessment of Dr Suyapto could not be utilised as a basis for the determination of entitlements because it did not comply with the relevant medical guidelines.
2. The application before the Tribunal is Ms Hanton's application for it to review that determination.

1. The dominant provision for the assessment of permanent impairment arising from a work injury is s 22 of the RTW Act.[4] It sets out a scheme for assessing the degree of impairment and provides, relevantly:

(1) This section sets out a scheme for assessing the degree of impairment (being whole person impairment) that applies to a work injury that results in permanent impairment.

(a) must be made in accordance with the Impairment Assessment Guidelines; and

(b) must be made by a medical practitioner who holds a current accreditation under this section.

(3) The Minister will publish guidelines (the Impairment Assessment Guidelines) for the purposes of the assessment of permanent impairment (being whole person impairment).

(a) must be published in the Gazette; and

(b) may adopt or incorporate the provisions of other publications, whether with or without modification or addition and whether in force at a particular time or from time to time; and

(c) must incorporate a methodology that arrives at an assessment of the degree of impairment of the whole person (whole person impairment); and

(d) may specify procedures to be followed in connection with an assessment; and

(f) may be amended or substituted by the Minister from time to time.

(7) An assessment of the degree of impairment resulting from an injury -

(a) must not be made -

(i) until there is evidence that the injury has stabilised; or

(ii) unless -

• (A) the injury is a condition prescribed for the purposes of this subparagraph by a regulation made on the recommendation of the Minister (see subsection (7a)); and
• (B) any requirement prescribed by the regulations has been satisfied; or

(iii) unless the injury is a terminal condition;

(b) must, subject to subsection (8), be based on the worker's current impairment as at the date of assessment, including any changes in the signs and symptoms following any medical or surgical treatment undergone by the worker in respect of the injury; and

(c) must be made by an accredited medical practitioner selected in accordance with the Impairment Assessment Guidelines.

(8) An assessment must take into account the following principles:

(a) if a worker presents for assessment in relation to injuries which occurred on different dates, the impairments are to be assessed chronologically by date of injury;

(b) impairments from unrelated injuries or causes are to be disregarded in making an assessment;

(c) impairments from the same injury or cause are to be assessed together or combined to determine the degree of impairment of the worker (using any principle set out in the Impairment Assessment Guidelines);

(d) impairment resulting from physical injury is to be assessed separately from impairment resulting from psychiatric injury;

(e) in assessing impairment resulting from physical injury or psychiatric injury, no regard is to be had to impairment that results from consequential mental harm;

(f) in assessing the degree of permanent impairment resulting from physical injury, no regard is to be had to impairment that results from a psychiatric injury or consequential mental harm;

(g) any portion of an impairment that is due to a previous injury (whether or not a work injury or whether because of a pre-existing condition) that caused the worker to suffer an impairment before the relevant work injury is to be deducted for the purposes of an assessment, subject to any provision to the contrary made by the Impairment Assessment Guidelines;

(h) assessments are to comply with any other requirements specified by the Impairment Assessment Guidelines.

(10) Subject to subsections (12) to (15) (inclusive), if -

(a) a worker has had a whole person impairment assessment under this section; and

(b) another impairment from the same injury or cause develops or manifests itself after that assessment,

(c) will be assessed separately; and

(d) -

(i) will not be combined in any respect (whether under this section or sections 56 or 58) with the impairment or impairments that have already been assessed; but

(ii) may be combined with any other impairment from the same injury or cause that has also developed or manifested itself after the earlier assessment.

(12) Subsection (10) does not affect the requirement under subsection (8)(d) for impairment resulting from physical injury to be assessed separately from impairment resulting from psychiatric injury.

(13) Subsection (10) operates subject to any assessment made under Part 8 (and the exercise of any adjudicative function by the Tribunal or a court).

(14) An interim decision under section 21 will not be taken to constitute an assessment for the purposes of subsection (10).

(15) Subsection (10) does not apply in any circumstances prescribed by the regulations.

1. Section 56 of the RTW Act sets out the criteria to be entitled to a lump sum payment for economic loss. Sub-section 56(2) provides that an entitlement does not arise under the section if the workers' degree of WPI from physical injury is less than 5%. Sub-section 56(6) addresses circumstances where a reduction in the lump sum payment applies. It provides:

(a) a worker suffers a work injury that gives rise to an entitlement under this section; and

(b) the worker subsequently suffers -

(i) an aggravation, acceleration, exacerbation, deterioration or recurrence of the injury referred to in paragraph (a); or

(ii) a new work injury,

and the worker, as a result, has a second entitlement under this section,

there will be a reduction of the lump sum payable under this section in respect of the second entitlement by the amount of the payment for the earlier entitlement unless such a reduction is incorporated into the provisions of the Impairment Assessment Guidelines (and then this subsection will apply in relation to any third or subsequent entitlement in the same way in order to ensure that each lump sum previously paid is taken into account as new entitlements arise).

1. Sub-section 56(4) sets out a formula for the calculation of the lump sum entitlement. No issue was raised as to the construction and application of s 56(4) in this case.
2. Section 58 of the RTW Act concerns lump sum payments for non-economic loss. As in the case of entitlements to lump sum payments for economic loss, s 58(2) provides a threshold of at least a 5% WPI to be entitled to a lump sum payment for non-economic loss where there are physical work injuries.
3. Subsection 58(7) addresses circumstances of a reduction of the lump sum payable. It provides:

(a) a work injury consists of the aggravation, acceleration, exacerbation, deterioration or recurrence of a prior work injury; and

(b) compensation by way of lump sum has been previously paid under this section, or a corresponding previous enactment,

there will be a reduction of the lump sum payable under this section in respect of the injury by the amount of the previous payment unless such a reduction is incorporated into the provisions of the Impairment Assessment Guidelines.

1. The medical guidelines authorised in accordance with s 22 of the RTW Act are the IAG and AMA 5. Chapter 1.2 of the IAG states that they are based mainly upon AMA 5 where the injury to be assessed as to impairment is a physical injury. Chapter 1.3 provides that where there are differences, the IAG are to be used as the modifying document. Chapter 3 of the IAG addresses the lower extremity of the human body. In AMA 5 it is chapter 17 that addresses the lower extremities.
2. Chapter 17 of the IAG sets out the procedure to be followed for the assessor selection process. No issue was raised in this case with respect to that process.
3. Appendix 1 to the IAG provides notes for the requestor which includes definitions.

1. Ms Hanton identified the issue to be addressed as 'whether the assessor adopted the correct methodology in making the deductions and determining the final WPI for the left lower extremity converted'.[5] In order to address that matter, Ms Hanton identified issues as to 'whether the deductions in this case should be made at the LEI or WPI level and whether they should be made before or after combination'.[6]
2. Ms Hanton submitted the issues are to be determined by an analysis of the relevant provisions of the legislative scheme.
3. After referring to s 22(8)(b) and (g), Ms Hanton referred to the judgment of the majority in Paschalis v Return to Work Corporation of South Australia and Anor (Paschalis)[7] as authority for a statement of principle that whether s 22(a), (b) or (g) applies, a single clinical process is undertaken.[8] She submitted the approach of the Corporation is contrary to that statement of principle.
4. Ms Hanton acknowledged that both the IAG and AMA 5 treat the lower extremity as a single assessable body system. She contended however, that it would be erroneous to equate the body system as equivalent to the concept of the same part of the body as it appears in chapter 1.23 of the IAG. That provides:
   • 1.23 If the unrelated or previous injury is to the same part of the body as the work injury and is not related to the work injury, the requestor will ask the assessor to disregard the unrelated or previous injury, which means that the current permanent impairment attributable to both injuries is assessed but the degree of impairment attributable to the unrelated or previous injury is then deducted. ...

1. Ms Hanton also relied upon a similar reference to a 'part of the body' in chapter 1.24 which provides:
   • 1.24 If the requestor asks for any injuries to a part of the body to be 'deducted', the assessor assesses the permanent impairment of the affected part of the body by applying the methodology in the Guidelines then deducts the permanent impairment % attributable to such injury. ...

1. Ms Hanton submitted that as a matter of ordinary language, the hip and the knee joints are not the same part of the body. She also referred to the 'part of the body' as it appears in the definition of the word 'injury' in s 4(1) of the RTW Act. That provides, relevantly:

(1) In this Act, unless the contrary intention appears -

...

injury, in relation to a worker, means -

(a) any physical or mental injury including -

(i) deterioration or impairment of a limb, organ or part of the body, or of a physical, mental or sensory faculty; or

1. Ms Hanton submitted that, in context, the phrase 'or part of the body' must be something less than a single limb or an organ.
2. Ms Hanton also sought to rely upon chapter 3.7 of the IAG which relevantly provides:

When the Combined Values Chart is used, the assessor must ensure that all values combined are in the same category of impairment rating (i.e. % WPI, LEI, or FI)... Regional impairments of the same limb (e.g. several lower extremity impairments) should be combined before converting to % WPI. (emphasis added)

1. It was submitted that by reference to chapter 3.7 of the IAG an impairment cannot constitute a 'regional' impairment unless both stages of the process have been completed, including the application of the deduction. Ms Hanton contended chapter 3.7, by its text, recognises the combination of distinct impairments in the lower extremity body system. It was contended that, put another way, impairments to the left hip and knee, in this case, are treated by the IAG as distinct impairments to be combined before a conversion to a WPI.
2. Reference was made to the judgment of the Court of Appeal in Return to Work Corporation of the South Australia v Opie (Opie).[9] Ms Hanton accepted the judgment as authority for the proposition that impairments to different segments within the same region of the spine are to be treated as injuries to the same body part and deductions may apply. However, she contended that the judgment is not authority for the proposition that distinct impairments to different regions of the spine would be treated that way. In support of that submission, she referred to chapter 4.23 of the IAG which provides:

Within a spinal region (cervical, thoracic or lumbar), separate spinal impairments are not combined. The highest DRE category is chosen. Impairments in different spinal regions are combined using the combination tables...

1. The Corporation submitted that the relevant region of the body for the assessment of permanent impairment is the lower extremity. It was contended that, relevantly, in this case, it is comprised of injury to the hip and knee. The assessor is thereby required to assess all of the impairments to the region and only then undertake the process of deduction. It was submitted this is the methodological instruction contained in chapter 1.29 of the IAG. The Corporation also referred to chapters 1.21, 1.23, 1.24, 3.7, 3.8 and 1.48 as having contextual relevance.
2. The Corporation submitted that the paragraphs within chapter 1 of the IAG referred to, reflect the statutory principles in ss 22(8)(b) and 22(8)(g) of the RTW Act to ensure that a worker is an injured worker is assessed and compensated only for the impairment which arises from work injury.
3. Particular attention was drawn to the sentence within chapter 1.29 that 'the impairment from the pre-existing injury is then subtracted from the overall impairment rating'. It was submitted that this is a clear indication in the IAG that the process of deduction for a pre-existing injury only occurs after the overall impairment rating of all injuries and impairments to be combined, has been completed.
4. Reference was made to chapter 1.48 which provides that regional body impairments are to be indicated in the report and then converted to % WPI in the summary table. The Corporation submitted this confirms that it is only at the final stage of the assessment that regional impairments are to be expressed as a % WPI.
5. The Corporation emphasised the last sentence of chapter 3.7 that is 'Regional impairments of the same limb (e.g. several lower extremity impairments) should be combined before converting to %WPI'. It was contended this directs an assessor to assess all the impairments within a region and where applicable, undertake combination before the LEI is converted to a WPI.
6. The Tribunal was invited to note chapter 3.8 of the IAG which provides that an assessed impairment of a part or region can never exceed the impairment due to amputation of that part or region. The Corporation contended it provides a clear policy rationale that impairments to a region cannot rise higher than the total loss of the relevant limb and thereby operates as an upper limit for any assessment applicable to a part or region.
7. The Corporation also drew attention to chapter 17.2a of the of AMA 5 which addresses conversions from a LEI to WPI. It provides relevantly:

Some individuals may have several impairments involving different parts of the same lower extremity; others may have several impairments of the same lower extremity part. If there are several impairments involving different regions of the lower extremity (e.g., the thigh and foot), evaluate each impairment separately, convert these regional impairments to hold person impairments, and combine the whole person impairment rating using the Combined Values Chart (p. 604). If there are multiple impairments within a region (e.g., the toes and the ankle), combine these regional, lower extremity impairments of the foot and convert the combined foot impairment to a whole person impairment. Similarly, when using separate methods on the same region, combine the regional impairments before converting to a whole person impairment rating.

1. The Corporation acknowledged chapter 17.2a of AMA 5 as not being entirely congruent with chapter 1.29 of the IAG. The Corporation submitted that whilst there are a number of tables in chapter 17 identifying the ratings applicable to the bodily systems expressed in terms of WPI percentages, LEI or specific factors or a combination of all three, what is required is a conversion to WPI before the Combined Values Chart is used to arrive at an overall percentage of WPI.
2. By reference to this construction, it was submitted that in the present case the hip and knee impairments are to be assessed separately and expressed as a LEI percentage. A LEI rating is then to be arrived at, and the final step is to convert the final LEI percentage to a percentage of WPI.
3. The Corporation referred to three interrelated policy rationales relevant to the construction of the provisions. The first was referred to is that a core feature of the scheme is to ensure consistency in assessments for all injured workers. The second is that the actual assessment of whole person impairment is to reflect the impairment arising from the work injury or injuries being assessed. The third is a statutory objective to ensure that compensation is appropriately targeted to the impact upon the region of the body being assessed. In this case it is the lower extremity.

1. As noted earlier in these reasons, s 22(1) of the RTW Act provides that the section sets out a scheme for the assessment of the degree of impairment in circumstances of a work injury that results in permanent impairment. Sub-section 22(7) refers to an assessment of the degree of impairment that results from an injury. Sub-section 22(2)(a) requires an assessment under the section to be made in accordance with the IAG. Under s 22(7)(c), an assessment of the degree of impairment resulting from an injury must be made by an accredited medical practitioner selected in accordance with the IAG.
2. The IAG comprise 17 chapters which deal with the assessment of injuries set out in body parts and systems. As already noted, it is chapter 3 concerning the lower extremity, which also refers to chapter 17 of AMA5, that is especially relevant to the assessment of permanent impairment in this case. Chapter 3 of the IAG and chapter 17 of AMA 5 are to be construed and applied in a manner consistent with the legislative scheme set out in s 22 of the RTW Act.
3. In this case, the assessment was required to take into account the principles established by ss 22(7) and 22(8) of the RTW Act. Sub-section 22(7)(b) required the assessment, subject to sub-section (8), to have been based upon Ms Hanton's current impairment at the time of the assessment by Dr Suyapto. Sub-section 22(8)(b) provides that impairments from unrelated injuries or causes are to be disregarded in making an assessment. Sub-section 22(8)(g) provides that any portion of an impairment that is due to a previous injury that caused the worker to suffer an impairment before the relevant work injury is to be deducted for the purposes of an assessment, subject to any provision to the contrary made in the IAG. It has been held that whilst the subsections address different factual circumstances, the purpose is the same. That is, only a work injury, or an impairment to the extent that it is attributed to a work injury, is to be assessed and be compensated.[10] In this case, Ms Hanton accepted that deductions applied to the left hip and left knee in accordance with s 22(8)(b) and (g) of the RTW Act.[11]
4. Subsection 22(8)(c) provides that impairments from the same injury or cause are to be assessed together or combined to determine the degree of impairment of the worker. That is to be achieved using any principles set out in the IAG.
5. The textual reference to a "deduction" in s 22(8)(g) indicates that the relevant process is to assess presenting impairment and then deduct impairment not attributable to the work injury. The textual reference in s 22(8)(c) to impairments from the same injury or cause being "assessed together or combined" indicates that in such cases, generally, such process is undertaken when assessing the presenting impairment in a body system.
6. The assessments of permanent impairment, by application of the IAG, are utilised for the purpose of determining various potential entitlements to compensation under the RTW Act. In this case, the significance is that the assessment will form the basis of the calculation of Ms Hanton's entitlements to lump sum payments for both economic loss and non-economic loss. More generally, s 21 of the RTW Act addresses seriously injured workers. The assessment of permanent impairment forms the basis of a determination of whether an injured worker qualifies to be treated as a seriously injured worker.[12] Part 5 of the RTW Act addresses claims for damages at common law. No such claim may be pursued against an employer unless the WPI, as assessed in accordance with s 22 of the RTW Act, reaches the threshold set out in s 72(1).
7. The foreword to the IAG identifies their purpose. It states:

The guidelines are intended to provide an objective, fair and consistent method for assessing permanent impairment arising from a work injury.

1. In Frkic v Return to Work Corporation of South Australia (Frkic),[13] the Full Bench of this Tribunal observed:

An important element of the assessment of whole person impairment under the RTW Act is to standardise the methods of assessment. In some instances radiological findings give rise to a percentage of impairment without regard to the individual functional impact of the findings. This is part of an overall scheme involving generally a single assessment and prescribed steps relating to that assessment. An important object of the assessment is to reduce the risk of disputed proceedings. Objective evidence rather than subject outcomes is a feature.[14]

1. The guidelines in AMA 5 are broader in their potential scope of application. Chapters 1.7 and 1.8 of AMA 5 refer to their use generally in the area of workers compensation. Chapter 1.9 refers to their use in addressing some of the implications of medical impairment towards a return to work in the future. Chapter 1.12 sets out a summary of the chapter. It confirms that AMA 5 is a set of guidelines. It directs the physician to comply with prescribed local, state, and federal practices for impairment evaluations. The purpose of AMA 5 is summarised in the following statement:

Combining the medical and non-medical information, including detailed information about essential work activities if requested, is a basis for improved understanding of the degree to which the impairment may affect the individual's work ability.

1. The methodology utilised by Dr Suyapto was largely by reference to chapter 17 of AMA 5. I have referred to chapter 1.3 of the IAG. Where there is a difference between AMA 5 and the IAG, the procedures in the IAG prevail to the extent of any inconsistency or difference from AMA5. Chapter 3 of the IAG commences with a statement that chapter 17 of AMA5 applies subject to the modifications that then follow in chapter 3 of the IAG. It is appropriate to address AMA 5 first, and then the modifications that appear in the IAG.
2. Before analysing the content of the relevant chapters of AMA 5 and the IAG, it is convenient to address the principles related to the construction and application of medical guidelines. The interpretation of AMA 5 and the IAG is a question of law.[15] AMA 5 and the IAG are forms of delegated legislation.[16] In construing AMA 5 and the IAG, the Tribunal will have regard to medical practitioners and not draft persons of statutes having prepared the documents.[17] In such circumstances the Tribunal will have particular regard to the plain words of the document.[18] AMA 5 and the IAG are to be construed by their terms and not more broadly in order to avoid what would otherwise be perceived as an unfair outcome.[19] AMA 5 and the IAG are to be construed in conformity with s 22 of the RTW Act and if any inconsistency is identified then the guidelines will generally yield to the proper construction of the RTW Act.[20]
3. If there is an inconsistency between the text within either AMA 5 or the IAG and an example that is given, then it is the text that will prevail.[21] In the context of the application of these legal principles, the determination of a level of impairment is a question of fact.[22]
4. Chapter 1.4 of AMA 5 addresses the philosophy and use of the CVC. It states:

The Combined Values Chart (p. 604) was designed to enable the physician to account for the effects of multiple impairments with a summary value. A standard formula was used to ensure that regardless of the number of impairments, the summary value would not exceed 100% of the whole person. According to the formula listed in the combined values chart, multiple impairments are combined so that the whole person impairment value is equal to or less than the sum of all the individual impairment values.[23]

1. In addressing the use of the CVC, Chapter 1.4 states:

In general, impairment ratings within the same region are combined before combining the regional impairment rating with that from another region. For example, when there are multiple impairments involving abnormal motion, neurologic loss, and amputation of an extremity part, these impairments first should be combined for a regional extremity impairment. The regional extremity impairment then is combined with an impairment from another region, such as from the respiratory system. Spinal impairments in multiple regions are combined. Exceptions, as detailed in the musculoskeletal chapter, include impairments of the joints of the thumb, which are added, as are ankle and subtalar joints in the lower extremity: both situations include complex motions.

1. The introduction to Chapter 17 of AMA 5 states that, for evaluation purposes, the lower extremities are divided into 6 sections but it then refers to "the feet, the hind feet, the ankles, the legs, the knees, the hips, and the pelvis". Chapter 17.2 refers to 13 methods that can be used to assess the lower extremities. They are listed in Table 17-2. Table 17-1 classifies the 13 methods into three non-mutually exclusive categories to reflect their primary mode of assessment. Those 3 categories are anatomic, functional or diagnosis based. Anatomic changes include range of motion, any limb length discrepancy, arthritis and other specific physiological changes. Diagnosis based estimates are used to evaluate impairments caused by specific fractures and deformities, as well as ligamentous instability, bursitis and various surgical procedures. Chapter 17.2 notes that, in certain situations, diagnosis-based estimates are combined with other methods of assessment. Functional impairments are chosen for conditions when anatomic changes are difficult to characterise or when functional implications have been documented.
2. Chapter 17.2j refers to a successful replacement of a hip as being a good example for a diagnosis based estimate of impairment. It states that hip replacements should first be rated using Table 17-34 and knee replacements using Table 17-35. Those tables were utilised by Dr Suyapto with respect to the hip and knee impairments respectively. In these circumstances, contrary to the opinion expressed by Dr Suyapto in his medical report dated 3 December 2024, chapter 1.38 of the IAG could not be applied to different approaches to the combination and deduction of impairments within the same method of assessment. Whilst factually this case is different to those addressed by the Court of Appeal in Opie, where it observed AMA 5 only provides for one method of assessment of impairment from a work injury to the lumbar spine, the Court of Appeal also observed that the principle that requires the use of the method which results in the highest degree of permanent impairment is not of general application.[24] Chapter 1.38 operates where the IAG and AMA 5 specify more than one equally valid, applicable method. In such a case, chapter 1.38 directs the assessor to use the method that results in the highest degree of permanent impairment. Dr Suyapto did not identify an alternate method of assessment, within the categories set out in chapter 17 of AMA 5, that results in a higher degree of permanent impairment.
3. As noted earlier in these reasons, chapter 17.2a addresses the conversion from LEI to WPI. Paragraph 43 of these reasons sets out the relevant text. Figure 17-10 of AMA 5 is a Lower Extremity Impairment Evaluation Record and Worksheet (LEIERW). It identifies the various regions of the lower extremity. The hip is a separate region from the knee. Chapter 17.2a by its text directed in this case that the impairment of the hip be evaluated separately from the impairment of the knee, that they be converted to WPIs and that the two WPIs be combined using the CVC.[25] That is consistent in part with the approach that was adopted by Dr Suyapto. He evaluated the hip impairment, including the deduction for pre-existing impairment, separately from the impairment of the knee where he similarly deducted the pre-existing impairment to that region. However, he combined the resultant LEIs before that result was converted from an overall LEI to a WPI.
4. The text of chapter 17.2a, in context, demonstrates how words such as a 'part' of a lower extremity or a 'region' of a lower extremity are to be understood within chapter 17 of AMA 5. In chapter 17.2a of AMA 5 there is a reference to different parts of the same lower extremity in the same paragraph where there is a reference to different regions of the lower extremity. Examples provided, and the identification of regions of the lower extremity in the LEIERW, also assist in the construction of that chapter.
5. The statements 'the same part of the body' in chapter 1.23 of the IAG and 'a part of the body' in chapter 1.24 are not defined in Appendix 1 to the IAG. They are to be interpreted in their relevant context. They are found in chapter 1, which is the introduction to the IAG. The introduction sets out principles of general application. Chapters 1.23 and 1.24 are not the methodology to be specifically applied for the assessment of permanent impairment in the case of injury to a lower extremity. They reflect the statement of legal principle established by s 22(8)(b) and s 22(8)(g) of the RTW Act that only a work injury, or an impairment to the extent that it is attributed to a work injury, is to be assessed and compensated. It was accepted by Ms Hanton that there is to be a deduction in this case for pre-existing impairments to her left hip and her left knee. The issue raised is the methodology to be applied.
6. As already addressed, there are requirements in the text of ss 22(7) and 22(8) of the RTW Act. The relevant chapters of the IAG are to be construed in a manner harmonious with the intent of those statutory provisions. Chapter 1.24 directs that the methodology to be applied for the deduction is that set out in the IAG. Relevantly, that methodology is set out in chapter 3. The text of chapter 3.7 of the IAG is materially different to the text of chapter 17.2 a of AMA 5. Chapter 3.7 directs the assessor to combine the regional impairments of the same limb (e.g. several lower extremity impairments) before there is a conversion to a % WPI. It is one of the modifications referred to at the commencement of Chapter 3 of the IAG. The modification is in the context of s 22(7)(b) of the RTW Act requiring an assessment based upon the worker's current impairment as at the date of the assessment and the agreed position of the parties in this case that the impairment to the left hip and left knee are to be assessed together or combined. These factors point to an assessment of the presenting and combined regional impairments of the left hip and knee, before the process of deduction is undertaken. It is to be noted this case involves the combination of regional impairments within the same body system and chapter of the IAG. The methodology to be applied may be different in circumstances of a combination of impairments where the impairments are to different body systems and different methods of assessment of presenting impairments and impairments to be deducted may apply.
7. Ms Hanton referred to the judgment of the Personal Injury Commission Appeal Panel in Milos The Handyman Pty Ltd v Djokic.[26] That judgment addressed New South Wales medical guidelines which are textually different to the IAG. The judgment was also in the context of a different statutory scheme. The judgment is not persuasive in the construction of the relevant provisions in this case.
8. I accept the submission of the Corporation that, by its text, chapter 3.7 provides the conversion to a % WPI as the final step in the assessment of the impairment. In this case, the IAG required the presenting regional impairments to the hip and knee of the same limb be assessed and combined as a LEI. The impairments not arising from the work injury to the same hip and knee were also to be assessed, combined and then deducted from the assessment of the presenting LEI. The final step, in accordance with chapters 1.23, 1.24 and 3.7 of the IAG was to convert the resultant LEI due to the left hip and left knee work injuries to a % WPI. As submitted by the Corporation, it is also consistent within the text of chapter 1.29 of the IAG which is of general application and states deduction is from the overall impairment. However, that does not add to the analysis of the correct methodology by reference to the submissions of both parties.
9. The Corporation also relied upon chapter 3.8 of the IAG which states that the assessed impairment of a part or region can never exceed the impairment due to amputation of that part or region. Chapter 3.8 has the effect of placing a limit upon the % WPI that may be assigned for an impairment of a lower extremity, noting the exception of where there is a hemipelvectomy, where a limit of 50% WPI applies. Whilst this may be generally consistent with the construction of the relevant provisions advanced by the Corporation, it also does not add to the analysis.
10. The construction of chapter 17 of AMA 5 and chapter 3 of the IAG set out in these reasons gives effect to the statutory intent of s 22(7)(b) and (8)(b)(c) of the RTW Act. Sub-section 22(7)(b) requires an assessor to assess the worker's current impairment as at the date of the assessment. Impairments not arising from the work injury are to be then disregarded or deducted in accordance with s 22(8)(b) and (g).
11. I reject the submission of Ms Hanton that the methodology found to be correct is not a single clinical process and inconsistent with the reasons of the majority in Paschalis. These reasons are consistent with the observation of the majority, that how injuries are to be assessed, not assessed or deducted, will depend on the circumstances.[27] In this case, the circumstances are in the context of the methodology provided by chapter 3 of the IAG. The methodology in chapter 3, as found, is a single clinical process undertaken by the assessor on the day of the assessment.
12. This is not a case where some deviation from the methodology set out in the IAG could be justified because "slavish adherence" would produce an "arbitrary, capricious or irrational result" when determining an accurate evaluation of underlying impairment.[28] The Corporation was correct to regard the methodology adopted by Dr Suyapto as not being in accordance with s 22 of the RTW Act and the applicable medical guidelines.
13. Paragraph 16 of these reasons sets out the agreed % WPI by reference to what has been found to be the correct methodology of assessment. Ms Hanton is entitled to be compensated pursuant to s 56 and s 58 of the RTW Act on the basis of a 19% WPI arising from work injury to the left hip and left knee sustained on 7 February 2019. Paragraph 16 also sets out the monetary entitlements that would be payable by the Corporation to Ms Hanton on that basis. The parties have agreed that she has an entitlement of $46,229 pursuant to s 58 and an entitlement of $15,968.15 pursuant to s 56. Noting that any future entitlements that Ms Hanton may have pursuant to either s 56 or s 58, should she sustain a further work injury, may need to have regard to her current entitlements and the basis of those entitlements, the parties shall be heard as to the form of orders now to be made in conformity with these reasons. The parties will also be heard in relation to any application for costs.

[1] AMA 5 contains tables which may be utilised to combine impairments within a body system. It also contains a Combined Value Chart (CVC) at pp 604-606 which may be utilised to combine assessments and impairments into a single overall impairment. Whether a table or the CVC is to be used depends upon the circumstances.

[2] In the case of lower extremity impairment, Table 17-3 at p 526 may be utilised to convert a percentage of an LEI to a percentage of a WPI.

[3] In general, as the percentage of WPI increases, the entitlement per percentage point also increases.

[4] Return to Work Corporation of South Australia v Preedy (2018) 131 SASR 86 pp 100, 104 & 107 (Stanley J (with whom Kourakis CJ and Parker J agreed)); Return to Work Corporation of South Australia v Summerfield (2021) 138 SASR 175 (Summerfield). See also the notation to s 22(8) of the RTW Act which provides that in taking into account the principles for assessment of permanent impairment, the subsection is to be interpreted and applied with the principles enunciated in Summerfield.

[5] Worker's outline of submissions [5].

[7] (2021) 140 SASR 77.

[8] Ibid 208-11 (Livesey and Bleby JJA).

[9] [2022] SASCA 12; (2022) 140 SASR 304.

[10] Paschalis supra [198] 123 (Livesey and Bleby JJ).

[11] Worker's outline of submissions, [4].

[12] See s 21(2) of the RTW Act. Such workers are not restricted to the limited periods of entitlement to both weekly payments and medical expenses that apply to other injured workers. See s 39(3) and s 41 of the RTW Act in relation to the entitlement period for weekly payments and s 33(20) and s 33(21)(a) in relation to the entitlement period for medical expenses.

[13] [2020] SAET 16.

[14] Ibid [48] (Farrell, Kelly and Rossi DPJJ) (cited with approval by the Court of Appeal in Return to Work Corporation of South Australia v Opie (2022) SASR 304, 322 [75] (Doyle, Livesey and Bleby JJA)).

[15] Frkic supra [18]; Barnett v Transport Accident Commission (1999) 15 VAR 414; [1999] VSC 484 [30] Where the reasons were affirmed and adopted in Barnett v Transport Accident Commission (2001) 34 MVR 26; [2001] VSCA 12.

[16] Frkic supra [19]; State Trustees Ltd v the Transport Accident Commission [2002] VSC 428; (2002) 6 VR 359, 365 [25]; Return to Work Corporation of South Australia v Papadopoulos (Papadopoulos) [2025] SASCA 48, [184] (Livesey P, S Doyle and Bleby JJA).

[17] Frkic supra [19]; Lake v Transport Accident Commission (No 2) [1998] 1 VR 616, 626; Martin v Return to Work SA [2016] SAET 95.

[18] Frkic supra [19]; Transport Accident Commission v Elworthy [2007] VSC 48, [21].

[19] Frkic supra [22]; GM Holden Ltd v Roberts [2013] SAWCT 15, [89]; HJ Heinz Company Australia Ltd v Kotzman [2009] VSC 311; Smoker v Pharmacy Restructuring Authority [1994] FCA 1487; (1994) 53 FCR 287; Kager v Return to Work SA [2019] SAET 220.

[20] Frkic supra [20]; Papadopoulos supra [184].

[21] Frkic supra [21]; Mountain Pine Furniture Pty Ltd v Taylor [2007] VSCA 146; [2007] 16 VR 659, 669 [33].

[22] Frkic supra [18]; Gillat v The Transport Accident Commission (2003) 38 MVR 463; [2003] VSC 15; Return to Work Corporation of South Australia v Sweeney (Sweeney) [2025] SASCA 50 [87] (Livesey P, S Doyle and Bleby JJA); Paschalis supra [212] (Livesey and Bleby JJ).

[23] The formula referred to is set out in the glossary to AMA 5 at p 600 which states:

'Combined Values Chart a method used to combine multiple impairments, derived from the formula A+ B(1-A) = combined values of A and B, which ensures that the summary value will not exceed 100% that's the percentage symbol and normal typing of the whole person.'

[24] Opie supra p 307 [3] (Doyle, Livesey and Bleby JJA).

[25] See especially the statement "if there are several impairments involving different regions of the lower extremity (e.g. the thigh and the foot), evaluate each impairment separately, convert these regional impairments to whole person impairments and combine the whole person impairment rating using the Combined Values Chart (p. 604)." The LEIERW identifies the hip as a separate region of the lower extremity to the knee.

[26] [2024] NSWPICMP 190.

[28] Sweeney supra [98] and the authorities there referred to.