1. On 31 January 2025, Anne Catherine Angel (the appellant) lodged an Application to Appeal Against the Decision of a Medical Assessor. The medical dispute was assessed by Dr Robert Kuru, a Medical Assessor, who issued a Medical Assessment Certificate (MAC) on

6 January 2025. 2. The appellant relies on the following grounds of appeal under s 327(3) of the Workplace Injury Management and Workers Compensation Act 1998 (the 1998 Act): * the assessment was made on the basis of incorrect criteria, and * the MAC contains a demonstrable error. 3. The delegate is satisfied that, on the face of the application, at least one ground of appeal has been made out. The Appeal Panel has conducted a review of the original medical assessment but limited to the grounds of appeal on which the appeal is made. 4. Rule 128 of the Personal Injury Commission Rules 2021 (the PIC Rules) and Procedural Direction PIC7 - Appeals, reviews, reconsiderations and correction of obvious errors in medical disputes set out the practice and procedure in relation to the medical appeal process under s 328 of the 1998 Act. An Appeal Panel determines its own procedures in accordance with r 128(1) of the PIC Rules. 5. The assessment of permanent impairment is conducted in accordance with the SIRA NSW Workers Compensation Guidelines for the Evaluation of Permanent Impairment, 4th ed

1 March 2021 (the Guidelines) and the American Medical Association Guides to the Evaluation of Permanent Impairment, 5th ed (AMA 5).

1. The appellant, who is 67 years old, was employed by State of NSW (Murrumbidgee Local Health District) (the respondent) as an enrolled nurse for a period of approximately 30 years.
2. The appellant said that approximately two to three years before her injury she started having pain in both knees with the right worse than the left. The condition did not prevent the appellant from performing her normal duties, attending to her house work or shopping. The appellant managed the pain with Panadol Osteo and rated her pain at about 2/10.
3. On 30 June 2020, the appellant bent down to assist a patient when she lost balance and started to fall. A colleague grabbed the appellant by the left arm to stop her from falling but, in the process, the appellant twisted and pressure was placed through her left knee. The appellant noticed an immediate sharp pain in the left knee.
4. Liability for an injury to the appellant's left knee was accepted by the respondent's insurer.
5. The appellant's knee injury was treated conservatively initially. The appellant was eventually referred to orthopaedic surgeon, Dr Andrew Redgment, who proceeded with a left total knee replacement on 28 April 2022.
6. On 2 February 2024, the appellant's solicitors served a claim for lump sum compensation pursuant to s 66 of the Workers Compensation Act 1987 (the 1987 Act). The appellant relied on an assessment of permanent impairment made by orthopaedic surgeon, Dr Russell Miller, dated 1 November 2023. Dr Miller found the appellant had 20% whole person impairment (WPI) at the left knee. Dr Miller made a 1/10 deduction for pre-existing injury, condition or abnormality pursuant to s 323 of the 1998 Act, leaving a total 18% WPI.
7. The claim for lump sum compensation was disputed in a notice issued pursuant to s 78 of the Workplace Injury Management and Workers Compensation Act 1998 (the 1998 Act) on 28 May 2024. The respondent did not accept that the injury had resulted in more than 10% permanent impairment as required by s 66(1) of the 1987 Act. The respondent relied on an assessment by orthopaedic surgeon, Dr Ron Haig, dated 17 April 2024. Dr Haig also found 20% WPI at the left knee but applied a 100% deduction pursuant to s 323 of the 1998 Act.
8. Proceedings were commenced in the Personal Injury Commission (Commission) on

16 October 2024. The medical dispute was referred by a delegate of the President to the Medical Assessor on 11 November 2024. 9. The Medical Assessor examined the appellant on 29 November 2024 and issued the MAC on 6 January 2025. Like Dr Miller and Dr Haig, the Medical Assessor found a 20% WPI at the left knee. The Medical Assessor took a history of pre-existing osteoarthritis at the left knee as follows:

"Ms Angel denies any previous injuries to her knees. I note in the clinical correspondence from Dr Matthews dated 2 May 2017, Ms Angel twisted her knee at home on her way to work. An MRI at the time demonstrated significant medial compartment osteoarthritis with a degenerative meniscal tear. At subsequent review by another Orthopaedic Surgeon, Dr Koo dated 5 July 2018, he notes presentation with bilateral knee pain and x-rays demonstrating bilateral varus osteoarthritis of both knees."

1. The Medical Assessor noted the competing deductions for the pre-existing condition made by Mr Miller and Dr Haig.
2. The Medical Assessor said the pre-existing condition was relevant because:

"Ms Angel had been symptomatic from osteoarthritis in her knees since 2017. Imaging at that stage demonstrated identical pathology."

1. In determining the proportion of impairment that was due to the pre-existing condition, the Medical Assessor stated:

"Whilst the extent of the deduction is difficult or costly to determine the available evidence is that the deductible proportion is large and a deduction of one tenth is at odds with the available evidence. In my opinion the deductible proportion is three-quarters for the following reasons:

(i) Ms Angel had established osteoarthritis in her left knee, for which it was concluded prior to her injury that ultimately she would be a candidate for knee replacement. The reason she had not had knee replacement surgery prior to her injury was the belief that she should use the intervening period to correct reversible lifestyle factors to improve the outcome from surgery. Her injury at work did not significantly change the timing, nor the nature of the intervention for the pre-existing condition."

1. The Appeal Panel conducted a preliminary review of the original medical assessment in the absence of the parties and in accordance with the Procedural Direction PIC7.
2. As a result of that preliminary review, the Appeal Panel determined that it was not necessary for the worker to undergo a further medical examination because the Appeal Panel had sufficient material before it on which to resolve the appeal.

1. The Appeal Panel has before it all the documents that were sent to the Medical Assessor for the original medical assessment and has taken them into account in making this determination.

1. The parts of the MAC given by the Medical Assessor that are relevant to the appeal are set out, where relevant, in the body of this decision.

1. Both parties made written submissions. They are not repeated in full, but have been considered by the Appeal Panel.
2. In summary, the appellant submits that the Medical Assessor erred in stating that the appellant's knee had been symptomatic from osteoarthritis since 2017 and that imaging at that stage had demonstrated "identical pathology". The appellant observed that the Medical Assessor did not have the benefit of any imaging at the time of his assessment. Imaging reports were, however, attached to the Application to Resolve a Dispute. Imaging in 2020 revealed a "complete rupture of the ACL with fibre fraying". In contrast, an MRI report in 2017 stated that the ACL "could not clearly be seen".
3. The appellant submitted that the MRI reports demonstrated a clear difference in pathology. The finding that the imaging demonstrated identical pathology was a demonstrable error.
4. The appellant further submitted that the Medical Assessor had applied incorrect criteria in determining the deductible proportion. In particular, the Medical Assessor had commented that the appellant had previously been considered a candidate for knee replacement and the injury did not significantly change the timing or the nature of intervention for the pre-existing condition at the left knee.
5. The appellant submitted that the only relevant treating report was that of Dr Khoo, dated

5 July 2018, which indicated that non-operative treatment was to be maximised and that the appellant should undergo bilateral injections. Arthroplasty would be considered if non-operative treatment failed. 6. The appellant's own evidence had been that she had been able to perform her normal duties and manage her symptoms with Panadol Osteo. After the injury, the appellant was unable to put full weight on the knee and required the use of a crutch and brace. The appellant submitted that the lack of evidence for the Medical Assessor's reasoning demonstrated that the determination of the deductible proportion was based on incorrect criteria. 7. In opposing the appeal, the respondent submitted that the Medical Assessor had the imaging reports although he did not have the actual MRI images. While the ACL could not clearly be seen in 2017 that did not mean there was no rupture of the ACL at the time but rather an issue with the clarity of the imaging. Otherwise, the MRI reports were identical and there was no demonstrable error. 8. With regard to the deductible proportion, the respondent submitted that the MAC was to be read as a whole and ought not to be read with an eye keenly attuned to the perception of error.[1] 9. The respondent submitted that the Medical Assessor provided adequate reasoning as to the deductible proportion. Furthermore, the opinion was consistent with the balance of the evidence. 10. Dr Haig had noted a long history of left knee symptoms including an entry in the general practitioner's notes dating back to 12 February 2012. There was a further entry dated

18 June 2018. Dr Haig did not consider the incident at work would have caused any pain in a knee that was not already severely compromised. The degree of arthritis prior to the injury would have destined the appellant for a knee replacement in the not-too-distant future.

Dr Haig had explained why he did not consider Dr Miller's 1/10 deduction appropriate. 11. The respondent submitted that the Medical Assessor's findings were open to him, based on the evidence and his clinical examination of the appellant. The reasons for the decision were plainly explained.

1. The procedures on appeal are contained in s 328 of the 1998 Act. The appeal is to be by way of review of the original medical assessment but the review is limited to the grounds of appeal on which the appeal is made.
2. In Campbelltown City Council v Vegan [2006] NSWCA 284 the Court of Appeal held that the Appeal Panel is obliged to give reasons. Where there are disputes of fact it may be necessary to refer to evidence or other material on which findings are based, but the extent to which this is necessary will vary from case to case. Where more than one conclusion is open, it will be necessary to explain why one conclusion is preferred. On the other hand, the reasons need not be extensive or provide a detailed explanation of the criteria applied by the medical professionals in reaching a professional judgement.
3. The evidence before the Medical Assessor was consistent with a pre-existing condition at the appellant's left knee.
4. The clinical records from Your Health Griffith indicated that prior to the work injury, the appellant had consulted her general practitioner for severe left knee pain in the absence of a fall on 14 February 2012. The appellant was prescribed Panadeine Forte. A sudden onset of right knee pain while standing and twisting was noted on 16 February 2012.
5. On 4 March 2013, it was noted that the appellant needed to see a physiotherapist for a knee cyst and arthritis.
6. On 21 March 2017, the appellant reported that she had sustained twisting injury to her left knee on 5 March 2017 when putting on her shoe. An MRI scan was noted to have revealed a baker's cyst with a tear of the medial meniscus. On examination, the appellant's general practitioner observed mild swelling. The appellant was referred to orthopaedic surgeon,

Dr Simon Matthews. 7. The report of the MRI of the left knee performed on 14 March 2017 noted that the image quality was somewhat degraded. The ACL could not clearly be seen. The medial meniscus demonstrated high signal change involving the mid body. 8. Dr Matthews prepared a report on 2 May 2017 in which he recorded a history as follows:

"... approximately five weeks ago she was getting ready to start a shift when she twisted her knee at home and felt significant medial sided pain shooting down towards her foot. The knee was so painful she was unable to put weight on it or bend it and she was seen in the Emergency Department that night. Over the course of the next couple of days with some pain relief, things settled down rapidly and she was able to start weight bearing on this and five weeks later her knee is pretty much back to normal. The knee itself feels like it will hold her up and does not display any further symptoms of locking. Prior to this she was diagnosed as having bilateral knee osteoarthritis."

1. Dr Matthews said an MRI showed significant full-thickness medial compartment cartilage loss and complete extrusion of the medial meniscus. Since things had settled down, Dr Matthews was of the view that the appellant had most likely just aggravated an arthritic joint.

Dr Matthews noted that the appellant was massively overweight with a BMI of 50 and recommended she lose weight urgently. 2. On 1 June 2017, the appellant reported ongoing knee pain to her general practitioner. The appellant was noted to require analgesia for her knee again on 29 July 2017 and

3 November 2017. 3. Ongoing bilateral knee pain was reported to the appellant's general practitioner on

18 June 2018. The general practitioner observed mild swelling at both knees and moderate pain. X-rays of both knees were requested. 4. The appellant was seen by orthopaedic surgeon, Dr Oliver Khoo, on 5 July 2018 complaining of left knee pain, worse than the right. The appellant reported trouble with her activities of daily living and pain with walking on stairs. The appellant was using Panadeine Forte and Nurofen Plus for her pain. Dr Khoo observed an antalgic gait, mild effusion, tenderness over the medial joint line bilaterally and patellofemoral crepitus. Dr Khoo said,

"We have discussed the options of management including maximising nonoperative treatment and when failing nonoperative treatment, arthroplasty of the knee. And will have injections bilaterally of steroid and local anaesthetic to her knees and I will review her in four weeks to assess the response."

1. On 30 July 2019, the appellant complained to her general practitioner of bilateral knee osteoarthritis. Ultrasound guided injections of both knees were requested and were expected to be performed in August 2019.
2. Following the work injury, the appellant was seen by her general practitioner on 7 July 2020. The appellant reported ongoing pain. On examination, an antalgic gait was observed. There was mild swelling and the appellant was unable to straighten the knee. The appellant was referred for a left knee MRI and prescribed Endone.
3. The report of an MRI of the left knee performed on 13 July 2020 noted a complex rupture of the ACL with fibre fraying. The medial compartment showed complete joint space cartilage loss with bone on bone contact. A complex macerated type tear of the medial meniscus was seen.
4. On 28 July 2020, the appellant was noted to be in moderate pain and walking with crutches. The appellant was prescribed Endone and Targin.
5. The appellant was seen by orthopaedic surgeon, Dr Frank Machart, at her solicitor's request on 25 March 2021. Dr Machart expressed the opinion that the injury on 30 June 2020 caused additional internal derangement, a medial meniscal tear and ACL rupture. These pathological changes were said not to be present on the previous MRI. The degenerative change was thought to be pre-existing.
6. The appellant was seen by another orthopaedic surgeon, Dr Graeme Doig, at the respondent's request on 29 September 2020 and 13 May 2021. Dr Doig said the appellant had severe pre-existing osteoarthritis of both knee joints which had been confirmed on medical imaging in 2018. The appellant had undergone treatment for this including intra articular cortisone injections.
7. The appellant medicolegal expert, Dr Miller, took a history of long-standing problems with both knees in his report, dated 1 November 2023. The symptoms were described to him as minor, manageable and allowing the appellant to continue work without difficulty. There was a marked deterioration in the left knee symptoms following the work injury.
8. Dr Miller referred to the radiological investigations, including the MRIs performed on

14 March 2017 and 10 July 2020. Dr Miller observed that a complete rupture of the ACL and complex macerated type tear of the medial meniscus were seen on the imaging dated

10 July 2020. 9. Dr Miller commented that the appellant had pre-existing arthritis in the left knee and a probable pre-existing medial meniscal tear. The appellant suffered further injuries to the knee with the rupture of the ACL and aggravation of the arthritis in the knee with the work incident. 10. The respondent's medicolegal expert, Dr Haig did not make any reference to the MRI imaging from 2017 nor any imaging from 2018, although he did have the reports of

Dr Matthews and Dr Khoo before him. Dr Haig referred to the entries in the clinical records from 14 February 2012 and 18 June 2018. Dr Haig expressed the opinion that the minor incident at work on 30 June 2020 would not of itself have caused any pain in a knee that was not already severely compromised. 11. Dr Haig commented on the assessment of impairment performed by Dr Miller, stating:

"I have read Dr Miller's report of 1 November 2023. Under the heading of past history, he states, 'Ms Angel states that she had longstanding problems with both knees. These symptoms were minor, manageable, and allowed her to continue working without difficulty. There is a marked deterioration in the left knee symptoms following the fall outlined above'. She did not fall. I agree with his assessment of a fair result for the left total knee replacement. He applied a 1/10 deduction. I believe her degree of arthritis pre-injury was such that she was destined for a knee replacement in the not-too-distant future and that 100% deduction is appropriate."

"323 Deduction for previous injury or pre-existing condition or abnormality

(1) In assessing the degree of permanent impairment resulting from an injury, there is to be a deduction for any proportion of the impairment that is due to any previous injury (whether or not it is an injury for which compensation has been paid or is payable under Division 4 of Part 3 of the 1987 Act) or that is due to any pre-existing condition or abnormality.

(2) If the extent of a deduction under this section (or a part of it) will be difficult or costly to determine (because, for example, of the absence of medical evidence), it is to be assumed (for the purpose of avoiding disputation) that the deduction (or the relevant part of it) is 10% of the impairment, unless this assumption is at odds with the available evidence.

So if the degree of permanent impairment is assessed as 30% and subsection (2) operates to require a 10% reduction in that impairment to be assumed, the degree of permanent impairment is reduced from 30% to 27% (a reduction of 10%)."

1. The approach to be taken in assessing the s 323 deduction was considered by the Supreme Court in Cole v Wenaline[2] where Schmidt J said:

"The section is directed to a situation where there is a pre-existing injury, pre-existing condition or abnormality. For a deduction to be made from what has been assessed to have been the level of impairment which resulted from the later injury in question, a conclusion is required, on the evidence, that the pre-existing injury, pre-existing condition or abnormality caused or contributed to that impairment.

Section 323 does not permit that assessment to be made on the basis of an assumption or hypothesis, that once a particular injury has occurred, it will always, 'irrespective of outcome', contribute to the impairment flowing from any subsequent injury. The assessment must have regard to the evidence as to the actual consequences of the earlier injury, pre-existing condition or abnormality. The extent that the later impairment was due to the earlier injury, pre-existing condition or abnormality must be determined. The only exception is that provided for in s 323(2), where the required deduction 'will be difficult or costly to determine (because, for example, of the absence of medical evidence)'. In that case, an assumption is provided for, namely that the deduction 'is 10% of the impairment'. Even then, that assumption is displaced, if it is at odds with the available evidence.

... as was discussed in the authorities, an earlier injury which was asymptomatic, may or may not contribute to the impairment which results from a second injury. That is a matter of fact to be assessed on the evidence led in each case.

...What must be determined on the evidence is whether any proportion of the permanent impairment present after the second injury was due to the earlier injury."

1. In Elcheikh v Diamond Formwork (NSW) Pty Ltd (in liq),[3] her Honour confirmed:

_"_As discussed in Cole v Wenaline Pty Limited at [30], in the case of a workplace injury caused by an exacerbation or acceleration of a pre-existing condition, what must be determined by a medical specialist under s 323 is:

• Firstly, what the extent of the resulting impairment is.
• Secondly, whether the pre-existing condition contributed to the impairment.
• Thirdly, if it did, what proportion of the impairment was due to the pre-existing condition."

1. The Medical Assessor's finding of 20% WPI at the left knee is uncontroversial, as is his finding that the appellant had a pre-existing condition at the left knee, which contributed to her impairment.
2. The appellant's submissions take issue with the Medical Assessor's finding that a 1/10 deduction was at odds with the available evidence and that a ¾ deduction was appropriate.
3. The appellant submits that there was a demonstrable error in the Medical Assessor's finding that the MRI imaging of the knee in 2017 showed identical pathology to that seen after the work injury in 2020. The respondent submits that, other than the ACL not being clearly visible in 2017, the pathology was the same in both investigations.
4. The MRI images were not before the Medical Assessor or the Appeal Panel, although the reports of the MRI investigations were. In the Appeal Panel's view, those reports do not support a finding that the pathology was "identical". The 2017 report was consistent with a medial meniscal tear, seen also on the 2020 investigations. However, it is simply not known what pathology was present at the ACL in 2017. In 2020, there was a clearly visible complete rupture of the ACL with fibre fraying. The two reports also demonstrate a progression of the osteoarthritic process at the knee.
5. The Appeal Panel agrees that the Medical Assessor's description of the pathology seen in 2017 as "identical" to that seen in 2020 was not accurate. That observation was not, however, the sole basis for the Medical Assessor's opinion. The Medical Assessor also formed the view that the work injury did not significantly change the timing, or the nature of the intervention for the pre-existing condition. The Medical Assessor commented that reason the appellant had not had knee replacement surgery prior to her injury was the belief that she should use the intervening period to correct reversible lifestyle factors to improve the outcome from surgery.
6. Although the respondent has submitted that the Medical Assessor's finding was open to him and the path of reasoning adequately explained, the Appeal Panel does not, with respect agree.
7. In July 2018 Dr Khoo gave the opinion that arthroplasty of the knee was a management option for the condition at the left knee if non-operative treatment failed. In the period that followed, the appellant returned to her work as a nurse. The appellant's evidence was that she worked seven days per fortnight for eight hours per shift, performing physical work including making beds, wheeling commodes and pushing patients in wheelchairs. The appellant's evidence was that she was able to cope with her normal duties at work, perform her activities of daily living and engage in her hobby of photography by using Panadol Osteo to manage her pain.
8. There are no further indications in the medical evidence that an arthroplasty was imminent although the Appeal Panel accepts that the appellant's knees remained symptomatic. Injections appear to have been performed in mid-2019 after a further complaint of pain to the general practitioner.
9. The medical evidence did demonstrate a change in the appellant's experience of symptoms at the left knee after the work injury on 30 June 2020. The appellant was prescribed Endone and Targin and was unable to straighten the knee. The appellant was non-weightbearing and using crutches.
10. The Medical Assessor did not engage with this evidence in finding that the injury did not significantly change the timing, or the nature of the intervention required at the left knee. While an arthroplasty had been foreshadowed as a possibility if non-operative interventions failed in 2018, the evidence described above suggested that the appellant had been coping with the non-operative interventions and that the increase in symptoms caused by the work injury brought forward the need for surgery.
11. By failing to adequately address this evidence, the Appeal Panel finds that there is a demonstrable error in the MAC.
12. The Appeal Panel also finds that the basis for the Medical Assessor's ¾ deduction was not consistent with the medical evidence. The reasoning employed by the Medical Assessor was consistent with Dr Haig's approach. However, Dr Haig did not engage with the change in the radiological findings or the appellant's experience of symptoms after the work injury.
13. The Appeal Panel agrees with the Medical Assessor's view that the extent of a deduction under s 323 is difficult to determine.
14. While there was significant pathology at the appellant's knee prior to the work injury, the evidence indicates that the appellant's symptomology settled down rapidly following the incident in March 2017 and the knee was "pretty much back to normal" according to

Dr Matthews by May 2017. Although the knee continued to be symptomatic, and required non-operative medical intervention in mid-2018 and mid-2019, the appellant's evidence was that she was able to function in an essentially normal way, most of the time, with only Panadol Osteo. 15. As noted above, this changed with the work injury, after which it was determined that an arthroplasty was required. 16. In the Appeal Panel's view, a 10% deduction is not at odds with the available evidence and should be applied consistently with s 323(2) of the 1998 Act. 17. Accordingly, the MAC should be revoked, and a new MAC should be issued. The new certificate is attached to this statement of reasons.

State of NSW (Murrumbidgee Local Health District)

This Certificate is issued pursuant to s 328(5) of the Workplace Injury Management and Workers Compensation Act 1998.

The Appeal Panel revokes the Medical Assessment Certificate of Medical Assessor Robert Kuru and issues this new Medical Assessment Certificate as to the matters set out in the Table below:

Chapter, page and paragraph number in NSW workers compensation guidelines

Chapter, page, paragraph, figure and table numbers in AMA 5 Guides

Proportion of permanent impairment due to pre-existing injury, abnormality or condition

Sub-total/s % WPI (after any deductions in column 6)

Total % WPI (the Combined Table values of all sub-totals)

The above assessment is made in accordance with the SIRA NSW Guidelines for the Evaluation of Permanent Impairment for injuries received after 1 January 2002.

[1] Minister for Immigration and Ethnic Affairs v Wu Shan Liang [1996] HCA 6.

[2] (2010) NSWSC 78.

[3] [2013] NSWSC 365.