WORKERS COMPENSATION - Workplace Injury Management and Workers Compensation Act 1998; assessment of permanent impairment following knee replacement surgery; Medical Assessor made section 323 deduction of one-third; claim in respect of a frank incident which resulted in meniscal injury; underlying osteoarthritis meant that only appropriate treatment was total knee replacement; no error in one-third deduction; Held - Medical Assessment Certificate confirmed.

1. On 6 January 2025 Maria Del Pino lodged an Application to Appeal Against the Decision of a Medical Assessor. The medical dispute was assessed by Medical Assessor Rob Kuru, who issued a Medical Assessment Certificate (MAC) on 17 December 2024.
2. Ms Del Pino 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 President's delegate was satisfied that, on the face of the application, at least one ground of appeal was made out, being that the MAC contains a demonstrable error. We conducted a review of the original medical assessment, 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. Ms Del Pino is employed by State of New South Wales (South Western Sydney Local Health District) (the Health District) as a registered nurse and midwife, working in neonatal intensive care at Liverpool Hospital. On 8 February 2021 she suffered an injury to her left knee when her foot became caught in the leg of a chair as she stood. She felt immediate strong pain and was investigated for deep venous thrombosis. She claimed compensation in respect of that frank incident and did not rely on the nature and conditions of her employment as being causative of her injury.
2. Ms Del Pino saw her general practitioner, Dr Kirkukli who ordered an MRI scan. The scan was reported on 17 September 2021 as showing:

"Mild medial femorotibial compartment osteoarthritis with low grade chondral wear throughout the central femoral condyle and posterior tibia! plateau along with small marginal osteophytes. Degeneration and extrusion of the body of the medial meniscus with surrounding oedema within the medial collateral ligament and mild pes anserine bursitis which is likely reactive. Further full thickness radial tear of the posterior horn of the medial meniscus adjacent to the root attachment.

Low grade chondral wear in the lateral femorotibial compartment Involving the central femoral condyle. Lateral meniscus is intact. Low grade chondral wear in the patellofemoral compartment involving Iha lateral patellar facet."

1. Dr Kirkukli referred Ms Del Pino to Prof Al Muderis, orthopaedic surgeon, whom she saw on 28 September 2021. Prof Al Muderis noted that she had no symptoms in her left knee before the injury. He reviewed the investigations and considered that she had acute on chronic changes with pre-existing arthritis but also with "some chondral flaps which have been sheared off in the medial compartment." He said:

"She does have a complex condition where there are pre-existing arthritic changes but superimposed with possible acute changes with more chondral damage on the medial side and expulsion of the medial meniscus of the posterior horn. Unfortunately, the combination of the age, being overweight, the chondral damage in the medial side, this is very difficult to treat so there is no option of doing keyhole surgery as it will be futile considering the level of arthritic changes in the knee."

1. Prof Al Muderis recommended conservative treatment for a period of six weeks but said that, if the arthritic disease progressed, knee replacement would be warranted.
2. Prof Al Muderis requested an X-ray and another MRI scan which were reported on 11 November 2021. The radiologist's conclusion on the MRI scan was:

Marked intrasubstance degeneration and attenuation of the posterior horn of the medial meniscus, presumably reflecting degenerative tearing.

Full thickness tear involving the posterior root ligament insertion of the medial meniscus.

Moderate arthrosis within the medial compartment of the tibiofemoral joint: Full thickness chondral wear within the central to posterior weightbearing surface of the medial femoral condyle; mild-grade chondral wear within the central to anterior weightbearing surface of the medial tibial plateau; mild subchondral bone marrow oedema at the periphery of the anterior, central and posterior weightbearing surfaces of the medial tibial plateau."

1. On 23 November 2021 Prof Al Muderis said that his clinical findings and the new MRI confirmed medial compartmental severe chondral damage and extrusion of the medial meniscus with narrowing of the joint space. He considered that the only treatment option was a total knee replacement and surgery was planned for 23 November 2021.
2. In a report to the Health District's insurer dated 20 January 2022, Dr Vasimalla, writing on behalf of Prof Al Muderis, said that the diagnosis of Ms Del Pino's condition was an "exacerbation of severe medial compartment osteoarthritis of the knee". He said:

"If the injury at work had not been sustained, there would be a chance that her pain and her symptoms would not be as significant and she may have been able to continue with conservative measures at this time and she may have avoided total knee replacement for some time."

1. Ms Del Pino saw Dr Solomon for a second opinion and he reported on 22 February 2022. He recorded a history of a twisting injury which resulted in ongoing medial knee pain. He noted that Ms Del Pino normally stood all day. He said:

"I have explained to Maria that there is no quick fix. Arthroscopic surgery will make her worse not better. The management of knee osteoarthritis and acute exacerbation of pain initially revolves around physiotherapy, weight reduction, anti-inflammatories and possibly even a steroid injection. All of these measures to help reduce pain but ultimately a knee replacement is the only effective solution.

Frankly I cannot see her getting back to her usual work activities without a total knee replacement."

1. Ms Del Pino's claim for the cost of total knee replacement surgery was disputed by the Health District. She saw Prof Al Muderis with Dr Siwicka, an orthopaedic fellow on 19 April 2022. Dr Siwicka prepared a report in which she said:

"We have discussed with Maria today that since non-operative methods have failed in order to alleviate her pain, she should consider surgical treatment for her left knee. We explained to her that keyhole surgery is not an option for her because of malalignment and the severe osteoarthritic changes making an arthroscopy of the knee an insufficient treatment for her. A realignment surgery such as high tibial osteotomy should also not be considered due to the involvement of the patellofemoral joint that is also contributing to her pain. A partial knee replacement is not an option since there is more than one compartment involved that has severe osteoarthritic changes. Similarly, to the consult in November 2021, we have again discussed with Maria the best surgical option would be a total knee replacement."

1. The Health District agreed to fund the cost of that surgery when proceedings were listed before the Personal Injury Commission on 15 September 2022. In a report obtained by Ms Del Pino's solicitors for those proceedings dated 31 August 2022, Prof Al Muderis said:

"The total knee replacement surgery which has been recommended for Maria has been after multiple attempts of non-operative conservative management of her knee condition. She had reported that she had sustained a twisting injury to her knee while she was at work as an NICU Nurse at Liverpool Hospital. Prior to that she had no symptoms in her knee and she used to walk without any problems, but since the twisting injury she had been struggling with her knee mobilisation and was in severe pain along the medial compartment and the patellofemoral compartment. I have not seen her prior to that consult so I cannot substantiate the extent of involvement of the knee prior to that injury, however it was evident from the imaging that the arthritis is not due to her workplace injury. The arthritis could have been due to her overall employment as she used to stand for long hours, she is on the heavier side and it can also be genetic. However, she did not have any symptoms prior to the twisting injury so there could be an acute on chronic exacerbation associated after the injury and that has resulted in acute decompensation and deconditioning of her knee which has resulted in her current situation."

1. The left total knee replacement was undertaken on 19 November 2022.
2. The Medical Assessor determined that Ms Del Pino had a fair result from total knee replacement surgery, resulting in an assessment of 20% WPI. He deducted one third under s 323 of the 1998 Act on the basis that Ms Del Pino would not have sustained a significant injury to her knee in the absence of the pre-existing condition, leading to 13% WPI. That amount was combined with Medical Assessor Lindsall's assessment of 4% WPI for scarring and a MAC was issued stating that Ms Del Pino had 16% WPI.
3. The appeal concerns the s 323 deduction only.

1. We 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, we determined that it was not necessary for Ms Del Pino to undergo a further medical examination because there is sufficient information in the file to determine the appeal.

1. We have all the documents that were sent to the Medical Assessor for the original medical assessment and have taken them into account in making this determination.
2. The parts of the MAC that are relevant to the appeal are set out below.

1. Both parties made written submissions. They are not repeated in full, but we have considered them.
2. In summary and in submissions prepared by Mr D King of counsel, Ms Del Pino submitted that the Medical Assessor failed to give adequate weight to the fact that she had no prior injuries to her left knee and was not experiencing symptoms before the injury. She submitted that he failed to have adequate regard to the extent that his assessment differed from the independent medical examiners who had examined her and failed to note why his opinion differed from other doctors about an MRI scan dated 11 November 2021. Ms Del Pino submitted that there was no evidence to suggest that any of the impairment present before the injury, and that it made no logical sense to apply one third deduction. She said that they should either be no deduction or a deduction of one-tenth.
3. In reply, and in submissions signed by its solicitor, Mr Marhaba, the Health District submitted that there was no error in the MAC and that a deduction of one-tenth would be at odds with the available evidence.

1. The procedures on appeal are contained in s 328 of the 1998 Act. The appeal is 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[1] the Court of Appeal held that an 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. In Queanbeyan Racing Club Ltd v Burton[2] the Court of Appeal held that an Appeal Panel is not limited to the ground held to have been made out by the delegate but may consider all grounds of appeal raised in the application. However, the panel is not permitted to look for errors which are not part of the grounds of appeal on which the appeal is made. We have only considered those grounds specifically raised by the appeal.

1. The Medical Assessor set out a short history and the subsequent treatment. He noted that Ms Del Pino has some ongoing symptoms:

"She has a constant ache in the front of the knee and along the joint line. She can walk about 200m or so. She has to negotiate steps one stair at a time."

1. The Medical Assessor set out his findings on examination, noting that Ms Del Pino looked well and was in no obvious distress. He said:

"Quadriceps circumference was 59cm and symmetrical. Gastroc circumference was 42cm and symmetrical. Her range of motion in the knee was from 0°-110°. The knee was in 5° of valgus. The knee was coronally and sagittally stable.

There was a 16cm scar over the front of the knee with some broadening and contour deficit.

The scar was consistent with the approach for total knee replacement. I was not asked to assess scarring.

The lower limb was distally neurovascularly intact."

1. The Medical Assessor commented on the MRI scan dated 11 November 2021 which he said showed:

"Medial compartment osteoarthritis with degenerative meniscal tear. Alignment films of the lower limbs show varus osteoarthritis left knee."

1. He said that an X-ray dated 19 November 2022 showed a total knee replacement without complication.
2. The Medical Assessor summarised the injury and diagnoses by saying that Ms Del Pino "twisted her knee at work and subsequently underwent total knee replacement". The Medical Assessor set out his calculations leading to a fair result under the Guidelines.
3. Commenting on the reports of the independent medical examiners, the Medical Assessor relevantly said:

"With respect to the report by Dr Papantoniou dated 21/02/2024, I have assessed the knee as a fair rather than poor result. I did not detect anteroposterior or mediolateral laxity in the joint at the time of my assessment...

With respect to the report by Dr Shahzad dated 27/06/2024, I am in agreement with assessment of the knee replacement as a fair result (20% whole person impairment)."

1. With respect to s 323, the Medical Assessor said:

"In the absence of the pre-existing condition, Ms Del Pino would not have sustained a significant injury to her knee. The impairment is on the basis of her having had an arthroplasty for constitutional osteoarthritis."

"As above, in the absence of a pre-existing constitutional condition, it is highly unlikely any significant impairment would have been assessable after the injury. The impairment is the consequence of treatment of the pre-existing constitutional condition not injury."

1. Ms Del Pino relied on a report from A/Prof Papantoniou dated 24 February 2024. He obtained the history that Ms Del Pino had no pain or restrictions before the injury. He noted that Ms Del Pino had returned to work on restricted duties and that she continued to suffer knee pain. He did not provide an opinion as to causation and considered the prognosis poor. The only MRI scan referred to was that dated 14 September 2021. He assessed a poor result from knee replacement surgery, assessing 30% WPI. He did not make a deduction under s 323 because there was "only mild osteoarthritis pre-injury noted on MRI post-injury".
2. The Health District relied on a report by Dr Shahzad dated 27 June 2024. At the time of his examination, he considered that Ms Del Pino's current physical symptoms were from age-related factors and were not a result of the injury. He assessed the knee replacement surgery as a fair result and deducted one-tenth under s 323, because there was pre-existing degeneration in Ms Del Pino's left knee and prognosticating when she would require a knee replacement is complex.

1. Ms Del Pino submitted that the Medical Assessor should have had greater regard to the extent to which his assessment differed from those of A/Prof Papantoniou and Dr Shahzad and that he should have explained why that was so.
2. The Medical Assessor is not required to adopt or choose between the other opinions in the file and is required to form his or her own opinion. In State of New South Wales (NSW Department of Education) v Kaur[3] Campbell J said:

"In Wingfoot Australia Partners Pty Ltd v Kocak [2013] HCA 43; 252 CLR 480, the High Court of Australia dealt with the nature of the jurisdiction exercised by a medical panel under cognate Victorian legislation. The legislation is not entirely the same but it is broadly similar in purpose. Allowing for some differences, the High Court said at page 498 [47]:

'The material supplied to a medical panel may include the opinions of other medical practitioners, and submissions to the Medical Panel may seek to persuade the Medical Panel to adopt reasoning or conclusions expressed in those opinions. The Medical Panel may choose in a particular case to place weight on the medical opinion supplied to it in forming and giving its own opinion. It goes too far, however, to conceive of the functions of the panel as being either to decide a dispute or to make up its mind by reference to completing contentions or competing medical opinions. The function of a medical panel is neither arbitral or adjudicative: It is neither to choose between competing arguments nor to opine on the correctness of other opinions on that medical question. The function is in every case to perform and to give its own opinion on the medical question referred to it by applying its own medical experience and its own medical expertise.'

Not all of this, as I have said, is apposite in the context of the New South Wales legislation. In particular, it is obvious that approved medical specialists are required to decide disputes referred to them by the process of medical assessment. Even so, it is not necessary that approved medical specialists should sit as decision makers choosing between the competing medical opinions put forward by the parties. Essentially, the function is the same as that described by the High Court in Wingfoot Australia. That is to say, their function is in every case to form and give his or her own opinion on the medical question referred by applying his or her own medical experience and his or her own medical expertise. It is sufficient, as their Honours pointed out at [55], that:

'The statement of reasons... explain the actual path of reasoning in sufficient detail to enable the Court to see whether the opinion does or does not involve any error of law.'"

1. The Medical Assessor is directed by the standard MAP template to comment on other opinions and provide the reasons why his or her opinion differs. That is so the parties understand how and why the assessment may differ, not because the Medical Assessor is required to agree with or choose between them.
2. The MAC is exceptionally short and the Medical Assessor's reasons are barely adequate. While his path of reasoning can be discerned, it could and should have been more fully explained. He did explain where his primary assessment differed from those of A/Prof Papantoniou and Dr Shahzad but did not do so with respect to s 323. We note that A/Prof Papantonio considered that the pre-existing medial compartment osteoarthritis was mild, though he commented only on the first MRI scan dated 14 September 2021 and not the later scan requested by Prof Al Muderis.
3. It does not follow that his assessment was not open to him in the exercise of his clinical judgement and the material in the file does support the deduction that the Medical Assessor made.
4. A deduction under s 323 can be appropriate in the absence of pre-existing pain and limitation. In Vitaz v Westform (NSW) Pty Ltd[4] Basten JA, with whom the other members of the Court agreed, rejected a construction that if a worker did not suffer symptoms from a pre-existing condition and there was no rateable impairment before an injury, there would be no deduction under s 323. His Honour said:

"That opinion contained a legal assumption which is inconsistent with the approach adopted by this Court in, for example, D'Aleo v Ambulance Service of New South Wales (NSWCA, 12 December 1996, unrep) (quoted by Giles JA, Mason P and Powell JA agreeing, in Matthew Hall Pty Ltd v Smart [2000] NSWCA 284; 21 NSWCCR 34 at [30]- [32] and, more recently, by Schmidt J in Cole v Wenaline Pty Ltd [2010] NSWSC 78 at [13]). The resulting principle is that if a pre-existing condition is a contributing factor causing permanent impairment, a deduction is required even though the pre-existing condition had been asymptomatic prior to the injury."

1. In Ryder v Sundance Bakehouse Campbell J said:[5]

"What s 323 requires is an inquiry into whether there are other causes, (previous injury, or pre-existing abnormality), of an impairment caused by a work injury. A proportion of the impairment would be due to the pre-existing abnormality (even if that proportion cannot be precisely identified without difficulty or expense) only if it can be said that the pre-existing abnormality made a difference to the outcome in terms of the degree of impairment resulting from the work injury. If there is no difference in outcome, that is to say, if the degree of impairment is not greater than it would otherwise have been as a result of the injury, it is impossible to say that a proportion of it is due to the pre-existing abnormality. To put it another way, the Panel must be satisfied that but for the pre-existing abnormality, the degree of impairment would not have been as great."

1. Southwell v Qantas Airways Limited[6] concerned the extent of the deduction under s 323. Wright J considered Cole v Wenaline Pty Ltd[7] and said:

"Thus, it has been held, in cases such as Elcheikh v Diamond Formwork (NSW) Pty Ltd (in liq) [2013] NSWSC 365 at [126] (Schmidt J) and Secretary, Department of Communities and Justice v Lewandowski [2023] NSWSC 334 at [52] (Griffith AJ), that what must be determined under s 323 involves, at least three enquiries:

• 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.

In light of the construction referred to above, however, the formulation of the second of these three enquiries may, in a case such as the present, misdirect consideration, if it were thought that all that had to be established was that the pre-existing condition was causally related in some way to subsequent workplace injury and the impairment suffered as a result of that injury, without any part or portion of that level of impairment being due to the pre-existing condition and not the injury."

1. We accept that Ms Del Pino was able to work as a registered nurse and midwife before the injury and that her left knee was asymptomatic. However, the investigations undertaken after the injury show that she did suffer osteoarthritis in her left knee. She has subsequently undergone an MRI scan of her right knee dated 13 May 2022 which also shows osteoarthritis.
2. The mechanism of injury that Ms Del Pino suffered - a twisting injury when her foot became caught in the leg of a chair - is the kind of injury likely to cause a meniscal tear. The diagnosis made by Prof Al Muderis on clinical and radiological grounds immediately after the injury was pre-existing arthritic change superimposed with acute changes with more chondral damage on the medial side and an injury to the medial meniscus. Prof Al Muderis considered whether keyhole surgery was warranted. We interpret that reference to mean that he considered whether arthroscopic meniscectomy and chondroplasty would resolve Ms Del Pino's pain and restriction of movement. He determined that it would not, because of Ms Del Pino's age and weight and because of the pre-existing changes.
3. The claim Ms Del Pino makes in these proceedings is based solely on the incident on 8 August 2021. She did not rely on the fact that she spent long periods on her feet at work. The incident on 8 August 2021 did not, of itself, warrant total knee replacement. The presence of osteoarthritis meant that treatment of the torn meniscus was not possible.
4. Each of Prof Al Muderis, Dr Solomon and Dr Shahzad considered that knee replacement would have been required at some time in the future for the underlying condition of Ms Del Pino's left knee. While it would have been better for the Medical Assessor to explain his conclusion more fully, he came to the same conclusion. The underlying condition precluded arthroscopic surgery and led to the total knee replacement. The permanent impairment now suffered is a result of that surgery.
5. The contemporaneous radiology read with the clinical findings soon after the injury allows for a determination to be made as to the contribution of the pre-existing condition of Ms Del Pino's left knee. Prof Al Muderis clearly set out his thought process as to the need for surgery. He was unable to treat only the acute injury because of the pre-existing condition.
6. The pre-existing condition therefore made a significant difference to the outcome. After joint replacement surgery, it is no longer possible to identify a proportion of the impairment due to the pre-existing condition because there is a new, resurfaced joint. The outcome of the surgery may vary from person to person and the extent of pre-existing osteoarthritis does not necessarily determine the outcome of the surgery. However, it is the pre-existing arthritis that leads to the need for joint replacement surgery.
7. If Ms Del Pino had undergone a successful medial meniscectomy to repair the damage caused by the event on 8 August 2021, her permanent impairment would be assessed at 1% WPI under Table 17-33 of AMA 5.
8. Because of the osteoarthritis observed on the MRI scan, it was open to the Medical Assessor to make a one-third deduction under s 323 in the exercise of his clinical judgement and the MAC does not contain a demonstrable error or reveal the application of incorrect criteria.
9. For these reasons, we have determined that the MAC issued on 17 December 2024 should be confirmed.

[1] [2006] NSWCA 284.

[2] [2021] NSWCA 304 at [26].

[3] [2016] NSWSC 346.

[4] [2011] NSWCA 254 at [43].

[5] [2015] NSWSC 526 at [45].

[6] [2024] NSWSC 497.

[7] [2010] NSWSC 78.