1. On 26 August 2025 Secretary Department of Education (the Department) lodged an Application to Appeal Against the Decision of a Medical Assessor. The medical dispute was assessed by Dr Philip Truskett, a Medical Assessor, who issued a Medical Assessment Certificate (MAC) on 30 July 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 ground(s) 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 D'Aubert relevantly made a claim for permanent impairment compensation resulting from injury sustained to her left lower extremity (left knee) in the course of her employment, with date of injury of 14 May 2013. Ms D'Aubert lodged an Application to Resolve a Dispute with the Personal Injury Commission (Commission) and the Department lodged a Reply and an Application to Admit Additional Documents. By consent, Ms D'Aubert's claim was remitted to the President for referral to the Medical Assessor for assessment of WPI resulting from the injury.
2. The Commission referred Ms D'Aubert's claim to the Medical Assessor and the Medical Assessor was provided with copies of the documents referred above for his review.
3. The Medical Assessor examined Ms D'Aubert on 14 July 2025 and the MAC in which the Medical Assessor assessed 18% whole person impairment (WPI) resulting from the injury

Ms D'Aubert sustained to her left lower extremity (left knee) with date of injury of

14 May 2013 issued on 30 July 2025. The Medical Assessor's assessment of 18% WPI included a one tenth deduction under s 323 of the 1998 Act for pre-existing injury, condition or abnormality.

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 is not of the view the Medical Assessor erred when assessing deduction under s 323 of the 1998 Act.

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 medical certificate 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 essence, the Department submits:

(a) the MAC contains a demonstrable error and/or the assessment by the Medical Assessor was made on the basis of an incorrect criteria;

(b) at least 50% deduction ought to have been applied of the substantive assessment by the Medical Assessor, thereby reducing the permanent impairment resulting from the incident occurring on 14 May 2013 to 9% WPI, and

(c) alternatively, Ms D'Aubert be re-examined by a member of the Appeal Panel.

(a) the Medical Assessor has taken into account, the difficulties which were evident when considering an appropriate deductible proportion. Before arriving at his conclusion, the Medical Assessor articulated his considered view of

Ms D'Aubert's history and surgical complexities, made his own observations of Ms D'Aubert's situation, and considered other medical opinions concerning

Ms D'Aubert's impairment, and

(b) the Medical Assessor's conclusion integrates the evidence consistently with the requirements of s 323 of the 1998 Act for the deduction of a portion of impairment resulting from pre-existing abnormality, which is demonstrated by radiological evidence.

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.

1. The Medical Assessor relevantly records the date of injury as 14 May 2013. While the Medical Assessor confirmed he had not been provided with any imaging studies which were not listed in the documents provided to him, it is evident the Medical Assessor had available to him an MRI scan report dated 14 August 2013 with the Medical Assessor providing comment on the radiologist's conclusion that "[T]hese are well established osteoarthritic changes. There was no acute trauma".
2. The Medical Assessor recorded the brief history of injury to Ms D'Aubert's left knee:

"On 14 May 2013 at approximately 4.00pm Mrs D'Aubert was supervising homework in the school library. She went to the toilet for a toilet break. The tiled floor was wet. She slipped, falling heavily on her left knee and left buttock. There was no head strike. She was in a great deal of pain and with some difficulty she was able to get out of the toilet and back into the room. She was assisted by a co-worker. She sat on a chair. She inspected her knee and noted it was grazed on the inner aspect and was starting to bruise. Soon after, she phoned the Principal and reported the incident. She went home."

1. The Medical Assessor noted Ms D'Aubert's general medical care under the care of

Dr Haque, and with a persistence of symptoms, her referral for specialist orthopaedic care under the care of Dr Pepper, who organised the MRI scan referred. The Medical Assessor noted that following review of the MRI scan, on 16 August 2013 Dr Pepper concluded "... she had exacerbated the arthritis of her knee". Ms D'Aubert initially had cortisone injection, with minimal response. Ms D'Aubert then had hyaluronic acid injection, with temporary relief.

Ms D'Aubert subsequently underwent left total knee replacement on 5 September 2018, following which she unfortunately developed deep vein thrombosis. With treatment,

Ms D'Aubert's deep vein thrombosis completely resolved, with ultrasound dated

3 October 2018 concluding "... [T]he previously seen soleal vein thrombus is no longer present. No sign of DVT...". However, with Ms D'Aubert's left knee still causing her pain, she came to left knee revision surgery on 23 November 2021 under the care of Dr Pepper. With Ms D'Aubert's left knee continuing to cause her pain, she was referred for specialist review by Dr Boyko, sports physician, under whose care she received steroid injection, with some benefit. The Medical Assessor noted Ms D'Aubert remains under the general medical care of Dr Haque and specialist care of Dr Pepper, although there is no planned treatment. 2. The Medical Assessor reported Ms D'Aubert denied "any prior injuries or pain in her left knee prior to her fall in the workplace in 2013". The Medical Assessor described Ms D'Aubert's present symptoms:

"Mrs D'Aubert has constant pain in her knee. Pain is present all the time. She would score this pain as 3/10 when good and 8/10 when bad. Pain will exacerbate with activity daily. It is particularly activated by walking more than 300m. She has a feeling of swelling in her knee. Her knee does not lock but did give way approximately 3 months ago on one occasion. She did not fall. She describes a slight twinge in her calf particularly when performing exercise. It is short-lived. It may occur when she is exercising with Pilates. Her calf does not swell."

1. Following clinical examination and review of the diagnostic investigation reports made available, the Medical Assessor relevantly provided summary of injuries and diagnosis as left total knee replacement secondary to osteoarthritis with patellar resurfacing.
2. Relevant to his evaluation of permanent impairment resulting from Ms D'Aubert's left knee injury, the Medical Assessor accepted Ms D'Aubert suffered pre-existing condition in her left knee, and said:

"At the time of presentation Ms D'Aubert had well established osteoarthritis of the left knee as witnessed by contemporaneous imaging."

1. Relevant to his assessment of WPI resulting from Ms D'Aubert's left knee injury, the Medical Assessor referred to Table 17-35, page 549 of the AMA 5 and considered Ms D'Aubert had achieved a "fair result, which is 50% impairment of the lower limb". While the Medical Assessor provided assessment of 20% WPI resulting from Ms D'Aubert's left knee injury he said:

"As there are pre-existing degenerative changes that were asymptomatic, a 10% deduction is considered appropriate. 10% of 20% is therefore 2%. 2% is then subtracted from 20%, which then equates to 18% whole person impairment."

1. In providing comment about other independent medical examiner opinions, the Medical Assessor relevantly noted:

(a) in his report dated 15 April 2024, Dr Hopcroft likewise provided 20% WPI resulting from Ms D'Aubert's left knee injury "but made no deduction for documented pre-existing degenerative change in the imaging provided". The Medical Assessor said, "I do not support this conclusion", and

(b) in his report dated 26 November 2020, Dr Hyde Page considered Ms D'Aubert had achieved a "good result" and provided 15% WPI resulting from Ms D'Aubert's left knee injury. Dr Hyde Page then made a two-thirds deduction, which the Medical Assessor said "might be considered excessive as she was asymptomatic prior to her injury. A 10% deduction, in my view, would seem more appropriate, given the lack of preceding pain." While Dr Hyde Page's opinion was provided prior to Ms D'Aubert coming to left knee revision surgery on 23 November 2021, in his subsequent report dated 31 October 2024 Dr Hyde Page now considered Ms D'Aubert had achieved a "fair result" and provided 20% WPI resulting from

Ms D'Aubert's left knee injury. Dr Hyde Page then again made a two-third's deduction, about which the Medical Assessor said "I believe to be excessive in the absence of pre-existing symptoms. In my opinion, a one tenth deduction would be more appropriate."

1. In her signed statement dated 12 June 2023 Ms D'Aubert described the circumstances of the injury she sustained to her left knee on 14 May 2013 in the course of her employment.

Ms D'Aubert described coming under the general medical care of Dr Haque, who she consulted with the following day, and with ongoing problems with her left knee she came under the specialist care of Dr Pepper, coming to left total knee replacement on

5 September 2018 and left knee revision surgery on 23 November 2021. 2. Ms D'Aubert makes no mention of any problems with her left knee prior to the incident occurring on 14 May 2013.

1. Dr ValKirychenko specialises in occupational medicine.
2. Dr ValKirychenko was provided with the opportunity to assess Ms D'Aubert in his capacity as independent medical consultant and in his report dated 21 July 2016, Dr ValKirychenko relevantly reported on the circumstances of Ms D'Aubert's left knee injury on 14 May 2013 and confirmed Ms D'Aubert told him "she had no previous left knee pain and was quite active on the left knee." At the time of assessment Ms D'Aubert was under the specialist care of

Dr Pepper with Dr Pepper's treatment plan being "to control her symptoms until they are so severe that he will have to do a knee replacement." 3. Dr ValKirychenko's report confirms no prior complaint by Ms D'Aubert of problems with her left knee prior to the incident occurring on 14 May 2013.

1. Dr Hyde Page is an orthopaedic surgeon. Dr Hyde Page was provided with the opportunity to assess Ms D'Aubert in his capacity as independent medical examiner and in his report dated

26 November 2020, Dr Hyde Page relevantly reported on the circumstances of

Ms D'Aubert's left knee injury occurring on 14 May 2013 and noted "she had never had any problems with her knee before". Dr Hyde Page accepted Ms D'Aubert aggravated a pre-existing condition in her left knee in the incident occurring on 14 May 2013. Despite Ms D'Aubert continuing to complain of left knee pain and numbness, Dr Hyde Page reported Ms D'Aubert had come to what he described as "a successful left total knee replacement due to the severity of the arthritic pain" under the care of Dr Pepper in September 2018. Dr Hyde Page's initial report confirms no prior complaint by Ms D'Aubert of problems with her left knee prior to the incident occurring on 14 May 2013. 2. In his report dated 31 October 2024 Dr Hyde Page noted that with Ms D'Aubert's left knee remaining problematic, Ms D'Aubert had come to left knee revision surgery under the care of Dr Pepper on 23 November 2021, following which she developed deep vein thrombosis, which resolved. Dr Hyde Page noted despite "a lot of physiotherapy" after her left knee revision surgery, Ms D'Aubert continued to experience pain and was referred to Dr Boyko with further physiotherapy treatment and exercise physiology. Following clinical examination, Dr Hyde Page provided opinion that despite the ongoing pain Ms D'Aubert suffered in her left knee "she has gone on to very good result with her left TKR, with a very good range of movement, strong quadriceps muscle power and stable, well aligned TKR." In response to specific questioning Dr Hyde Page confirmed:

"As I outlined in my original report, I consider the work injury she suffered to her left knee on 14 May 2013 was relatively minor. She went to the toilet and slipped and fell injuring her left knee. This was a minor low impact injury where she appears to have aggravated underlying osteoarthritis of the left knee that was reasonably well advanced. Her left knee deteriorated over the next few years as natural sequence or course of events of her already well-established osteoarthritis, and she ultimately had a total knee replacement in 2018. If she had not had the work injury to her left knee in May 2013, it is likely that she would have needed a left total knee replacement around about the same time due to natural progression of the osteoarthritis. Overall I stand by my original assessment, that two thirds of the need for a left total knee replacement was due to this pre-existing osteoarthritis and one third to her work injury.

... I have concluded there is a major non-work related factor to take into account in the left knee, where she had underlying osteoarthritis of the left knee, completely unrelated to her work injury. She has always led a very active lifestyle, living on a farm, riding horses and other outdoor activities that would have resulted in progression of her osteoarthritic left knee irrespective of the work injury in May 2013, which was a low impact injury to her left knee."

1. In providing assessment of WPI resulting from the injury Ms D'Aubert sustained to her left knee on 14 May 2013 Dr Hyde Page relevantly provided opinion:

"In her left knee, she has whole person impairment related to her left TKR. With reference to page 547 Table 17-33, she has a fair result with her total knee replacement due to ongoing pain... this gives 20% WPI. ... there is two thirds WPI due to pre-existent unrelated osteoarthritis and one third due to the work injury. One third of 20% is 6.7% and this rounds up to 7% WPI."

1. In providing comment on Dr Hopcroft's supplementary report dated 15 April 2024 referred below, Dr Hyde Page said:

"Dr Hopcroft in his supplementary report of 15 April 2024, has concluded that Jenifer D'Aubert has had a fair result in her total knee replacement giving 20% WPI. I agree with this assessment ... Dr Hopcroft has not made any deduction for any pre-existent injury or condition affecting the left knee. I have indicated in my report there is a major deduction for pre-existent osteoarthritis of the left knee, noting that the work injury suffered to the left knee was relatively mild as well. For this reason, I deducted two thirds the level of WPI."

1. Dr Hopcroft is an orthopaedic surgeon. Dr Hopcroft was provided with the opportunity to assess Ms D'Aubert in his capacity as independent medical examiner and in his report dated 2 September 2023, Dr Hopcroft reported on the circumstances of Ms D'Aubert's left knee injury occurring on 14 May 2013 and consequential treatment, including surgical treatment, under the care of Dr Pepper. At the time of writing his report Dr Hopcroft considered that assessment of WPI was premature but relevantly said "I can advise in advance that this patient has no problems ... with the function of her left knee prior to the injury of 14 May 2013".
2. In his subsequent report dated 15 April 2024, Dr Hopcroft provided opinion:

"By way of reference to Page 547, Table 17-33 and Page 549, Table 17-35, as this patient required revisionary surgery in the form of patellar liner to be undertaken following the necessary left total knee replacement procedure which was triggered as a result of her work-related injury of 14 June 2013, she can be deemed to have obtained a fair result from her surgical intervention and has a whole person impairment of 20% ... As the patient had no pre-existent problems with the function of her left knee or plans to have surgical intervention, I do not believe a subtraction is required in her overall whole person impairment assessment."

1. In his supplementary report dated 27 February 2025 following receipt of the reports of

Dr Hyde Page dated 26 November 2020, 18 December 2020 and 31 October 2024 referred above, Dr Hopcroft pointed out that in his report dated 26 November 2020, Dr Hyde Page had said of Ms D'Aubert "she had never had any problems with her knee before" prior to injuring her left knee on 14 May 2013 in the course of her employment. Dr Hopcroft noted "that very significant historical issues" appeared to have been overlooked by Dr Hyde Page when he provided his assessment of WPI resulting from the injury Ms D'

Aubert sustained to her left knee on 14 May 2023. Dr Hopcroft explained:

"It should be stated categorically that osteoarthritic changes can be found in any adult knees in any patient's aged 60, the patient's age at the time of her injury, and it is wrong to assume that such asymptomatic underlying pre-existing changes are likely to inevitably lead to joint replacement surgery, but Dr Hyde Page opted to subtract two-thirds of this patient's overall whole person impairment assessment in spite of that most significant negative finding in this patient's history.

The patient underwent two major procedures as a direct result of her fall which would not normally have been necessary had she not fallen in the course of her work on 14 May 2013, namely a left total knee joint replacement procedure as her left knee joint function slowly failed, and the patient, stopped working however the left knee slowly got worse, page 4 paragraph 3 of Dr Hyde Page's initial report.

Post operatively, with deterioration of the patellofemoral interface she required secondary surgery with left patellar prosthetic liner being applied to the articulate surface of her left patella, and thereafter the patient continued to have significant pain which both Dr Hyde Page and myself agree saw her with a whole person impairment due to the totality of her two operative procedures on her left knee joint at 20%.

As the patient had no pre-existing problems with the function of her left knee joint prior to the fall in the course of her walk in 2013, and had constant symptoms in her left knee joint thereafter, led me strongly to assert that this patient did not require a subtraction for pre-existing problems with her left knee joint."

1. The MRI scan of Ms D'Aubert's left knee performed on 14 August 2013 reportedly concluded:

"... No definite meniscal tear is identified in either compartment. Grade 4 articular cartilage defect in the medial compartment on both surfaces and grade 3-4 articular cartilage defect in the inner aspect of the medial facet of the patella and grade 2-3 defect in the lateral facet."

1. The clinical records of Tristar Medical Group-Kempsey relevantly confirm Ms D'Aubert consulted with Dr Haque on 15 May 2013 with a history of a workplace slip and fall the day before, with injury to her left knee. There is no prior history of left knee complaint since Ms D'Aubert commenced consulting with the doctors at the Medical Practice in late September 2011.

1. Dr Pepper has provided a number of reports during the course of Ms D'Aubert's claim for workers compensation resulting from injury she sustained to her left knee on 14 May 2013 in the course of her employment.
2. Dr Pepper is Ms D'Aubert's long-term treating orthopaedic surgeon and review of his reports demonstrated Ms D'Aubert made no prior complaint of left knee symptoms to him until

Ms D'Aubert consulted with him about her left knee after she sustained injury on

14 May 2013. 3. In his report dated 3 July 2013 Dr Pepper reported the circumstances of injury occurring on 14 May 2013:

"She slipped in the bathroom with her right foot out forwards, the left knee flexed, twisted and hit the tiled floor. She had immediate swelling in the knee, she hobbled around but did continue to work. She is very concerned because the knee hasn't fully settled, it is certainly a lot better but still quite painful."

1. In his report dated 16 August 2013 Dr Pepper reported that following review of the MRI

Ms D'Aubert underwent on 14 August 2013 "I believe she has exacerbated the arthritis in the knee more than any definite tear in her cartilage". 2. In his report dated 15 November 2013 addressed to the insurer and in response to specific questioning, Dr Pepper explained:

"1. Jenifer has inflammation of her left knee, with synovitis, and exacerbation of her pre-existing osteoarthritis. The MRI performed in August 2013 confirms no actual meniscal tear seen, however there is seen to be subchondral oedema and changes consistent with osteoarthritis. From the history give to me from Jenifer D'Aubert she had no pain in the knee prior to tine injury that she suffered at work. Therefore, this is an aggravation of a pre-existing condition.

1. With regards to the proportion of her current symptoms, according to the history provided by the patient, the pain was non-existent or minimal prior to the injury, and is now at such a level that she has not responded to simple treatments, and is looking at arthroscopic surgery. Therefore in theory the need for the arthroscope is completely due to the injury that she suffered at work. However I would like to point out that the work injury did not cause the osteoarthritis, it merely has brought the symptoms on a lot earlier than it would of occurred without the injury. It is extremely likely that she would have had pain at some stage in the future, it is just a case of the injury has brought the symptoms to light a lot earlier.
2. Therefore it's my opinion that this is a significant exacerbation of a pre-existing condition, that was minimally symptomatic. This is very common in osteoarthritic joints, particularly in knees, in so much as patients can have radiological evidence of arthrosis, but no pain for many years. Often it takes a single trigger or event for injury, the arthritic pain starts, the inflammation progresses, and patients unfortunately deteriorate quite rapidly. It is very common that patients then need to have arthroplasty surgery in order to solve their discomfort.
3. I believe Jenifer D'Aubert's employment is a contributing factor to her current level of symptoms, but certainly there is a pre-existing component. Therefore I believe that her employment is only partially responsible for the ongoing medical costs of her treatment. I do think it is reasonable that the insurers cover the costs of her arthroscopic surgery, with regards to future surgery however this would be almost inevitable though with the workplace injury, but perhaps may have been delayed for a few more years.
4. I do not believe there is any non work factors with regards to injury or falls or exacerbations that I am aware of that contribute to the current symptoms that she suffers in her knee.
5. The prognosis is reasonably poor in so much as I do believe she is looking at arthroplasty surgery. I have tried simple treatments with the Durolone Cortisone and physiotherapy but unfortunately she has not responded. An arthroscopic surgery may alleviate some of the symptoms, but she will remain in discomfort afterwards, but hopefully the pain is manageable such that she can continue as is for a few more years. Thus the point of the arthroscope really is a delaying tactic for the inevitable arthroplasty surgery in the future."
6. In his report dated 1 December 2015, also addressed to the insurer, Dr Pepper confirmed that while Ms D'Aubert had been a patient of his since 2003 she first consulted with him relevant to her left knee injury sustained on 14 May 2013 in the course of her employment, on 3 July 2013. Dr Pepper noted at the time of his examination "she had very slight joint space narrowing on the medial aspect of the knee consistent with very mild pre-existing osteoarthrosis". Following MRI scan on 14 August 2013, Dr Pepper provided opinion

Ms D'Aubert had "exacerbated pre-existing osteoarthrosis in the knee" in the incident occurring on 14 May 2013 and in response to specific questioning at that time Dr Pepper confirmed:

"I do believe that her workplace injury is responsible for the exacerbation of pre-existing osteoarthrosis in the knee. She had a major twisting impact type injury to the knee and previous to this had no significant discomfort nor pain. Whilst her workplace has not been responsible for the osteoarthrosis, this is an age and genetic related issue, it is responsible for bringing forward her symptoms earlier than would have without the injury at work."

1. Dr Pepper referred Ms D'Aubert to Dr Ragavan, senior rehabilitation consultant, with

Dr Ragavan noting in his report dated 6 November 2013 that Ms D'Aubert had suffered a fall the same year "and has been having left knee pain". Dr Ragavan made no mention of

Ms D'Aubert suffering left knee pain prior to her slip and fall on 14 May 2013.

1. Section 323 of the 1998 Act relevantly provides:

"(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 ... or that is due to any pre-existing condition.

(2) If the extent of a deduction under this section (or 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.

(3) The reference in subsection (2) to medical evidence is reference to medical evidence accepted or preferred by the medical assessor in connection with the medical assessment of the matter."

1. Chapter 1 of the Guidelines provides for deductions for pre-existing condition or injuries.
2. Clause 1.27 provides:

"The degree of permanent impairment resulting from pre-existing impairments should not be included in the final calculation of permanent impairment if those impairments are not related to the compensable injury."

"In assessing the degree of permanent impairment resulting from the compensable injury/condition, the assessor is to indicate the degree of impairment due to any previous injury, pre-existing condition, or abnormality. The proportion is known as 'the deductible proportion' and should be deducted from the degree of permanent impairment determined by the assessor. For the injury being assessed, the deduction is 1/10th of the assessed impairment, unless that is at odds with the available evidence."

1. At this point it is useful to note authority the Appeal Panel considers to be central to complaint made by the Department, particularly in circumstances where the Department has referred to both Cole v Wenaline Pty Ltd[1] and Ryder v Sundance Bakehouse.[2]
2. In Cole the court considered how a previous injury should be taken into account when determining assessment of permanent impairment following subsequent injury. The Appeal Panel accepts the court's decision in Cole has application when considering the application of s 323 of the 1998 Act in that the court found that assumptions should not be made when determining deduction due to prior injury, pre-existing condition or abnormality, rather, s 323 of the 1998 Act requires conclusion on the evidence that the prior injury, pre-existing condition or abnormality caused, or contributed to the resulting impairment.
3. Similarly, the Appeal Panel accepts the court's decision in Ryder when considering the application of s 323 of the 1998 Act in that the court explained the requirements for a deduction under s 323 of the 1998 Act:

"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 impossible to say that a proportion of it is due to the pre-existing abnormality."

1. The Appeal Panel notes the task of a Medical Assessor was described by the court in State of New South Wales v Kaur:[3]

"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..."

1. The Appeal Panel is mindful too that in Ferguson v State of New South Wales[4] the court cited with approval NSW Police Force v Daniel Wark[5] where the court said:

"The pre-eminence of the clinical observations cannot be underrated. The judgment as to the significant or otherwise of the matters raised in the consultation is very much a matter for assessment by the clinician with the responsibility of conducting his/her enquiries with the applicant face to face."

1. Justification of intervention by an Appeal Panel such as ours was also discussed by the court in Ferguson:[6]

"The Appeal Panel accepted that intervention was only justified: if the categorization was glaringly improbable; if it could be demonstrated that the AMS was unaware of significant factual matters; if a clear misunderstanding could be demonstrated; or if an unsupportable reasoning process could be made out. I understood that all of these matters were regarded by the Appeal Panel as interpretations of the statutory grounds of applying incorrect criteria or demonstrable error. One takes from this that the Appeal Panel understood that more than a mere difference of opinion on a subject about which reasonable minds may differ is required to establish error in the statutory sense."

1. The matter of Ferguson was cited with approval by the court in Parker v Select Civil Pty Limited.[7]
2. In determining the Department's appeal, the Appeal Panel is aware that in Campbelltown City Council v Vegan[8] the court held while the Appeal Panel is obliged to give reasons, the reasons need not be extensive or provide a detailed explanation of the criteria applied by the medical professionals in reaching a professional judgement.

1. Cole and Ryder demonstrate the process a Medical Assessor is required to follow in assessing deduction made under s 323 of the 1998 Act:

(a) the level of an injured worker's impairment must be determined at the time of assessment;

(b) a prior injury or pre-existing condition must be identified;

(c) it must be determined whether a proportion of the worker's post injury impairment is due to the prior injury or pre-existing condition, and

(d) the extent to which the worker's post-injury impairment is due to the prior injury or pre-existing condition must be determined.

1. At the time of assessment, the Medical Assessor assessed Ms D'Aubert with 20% WPI resulting from the injury she sustained on her left lower extremity on 14 May 2013. Neither the Department of Ms D'Aubert quibble with this assessment.
2. The Medical Assessor identified Ms D'Aubert suffers pre-existing osteoarthritis in her left knee, which he said was "witnessed by contemporaneous imaging" being reference to the MRI scan report dated 14 August 2013. Neither the Department nor Ms D'Aubert quibble with the Medical Assessor's identification of the pre-existing osteoarthritis Ms D'Aubert suffers in her left knee.
3. Although it is evident Ms D'Aubert made no complaint of symptoms in her left knee prior to the incident occurring on 14 May 2013, the Medical Assessor accepted, as did Dr Hyde Page, that a proportion of Ms D'Aubert's post injury impairment is due to the pre-existing osteoarthritis. While Dr Hopcroft was strident in opinion that as Ms D'Aubert had no pre-existing problems with the function of her left knee prior to 14 May 2013 and had constant symptoms thereafter there should be no deduction under s 323 of the 1998 Act for the pre-existing osteoarthritis Ms D'Aubert suffers in her left knee, the Medical Assessor accepted there should be a deduction under s 323 of the 1998 Act for the pre-existing osteoarthritis

Ms D'Aubert suffers in her left knee. Neither the Department nor Ms D'Aubert quibble with the Medical Assessor's determination that a portion of Ms D'Aubert's post injury impairment is due to the pre-existing osteoarthritis Ms D'Aubert suffers in her left knee. 4. The Medical Assessor made a one tenth deduction under s 323 of the 1998 Act and it is the Medical Assessor's determination of this extent to which Ms D'Aubert's post injury impairment is due to the pre-existing osteoarthritis Ms D'Aubert suffers in her left knee with which the Department quibbles. While Dr Hyde Page made a two thirds deduction under s 323 of the 1998 Act the Medical Assessor provided comment that he believed the deduction Dr Hyde Page made "to be excessive in the absence of pre-existing symptoms" and that "a one tenth deduction would be more appropriate, given the lack of preceding pain." 5. It is evident the Medical Assessor has followed the process required of him when determining deduction under s 323 of the 1998 Act due to the pre-existing osteoarthritis

Ms D'Aubert suffers in her left knee, as outlined in Cole and Ryder. 6. Based on the evidence available to the Medical Assessor at the time of his examination of Ms D'Aubert on 14 July 2025, which included reporting from Ms D'Aubert's treating practitioners as well as reporting from independent medical examiners, and his own clinical observations, the Medical Assessor determined the pre-existing osteoarthritis Ms D'Aubert suffers in her left knee made a difference to the permanent impairment Ms D'Aubert suffered in her left knee, despite the fact that Ms D'Aubert's pre-existing osteoarthritis had been asymptomatic prior to 14 May 2013, and determined a one tenth deduction under s 323 of the 1998 Act to be appropriate. 7. While Dr Hopcroft made no deduction under s 323 of the 1998 Act and Dr Hyde Page made a two-thirds deduction under s 323 of the 1998 Act, the Medical Assessor is required to apply his own medical experience and medical expertise and provide his own opinion when determining deduction under s 323 of the 1998 Act, which the Medical Assessor has done with reasoning. 8. For the reasons canvassed above, the Appeal Panel has determined that the MAC issued on 30 July 2025 should be confirmed.

[1] [2010] NSWSC 78 (Cole).

[2] [2015] NSWSC 526 (Ryder).

[3] [2016] NSWSC 346.

[4] [2017] NSWSC 140 (Ferguson).

[6] [2017] NSWSC 140 (Ferguson).

[7] [2018] NSWSC 140.

[8] [2006] NSWCA 284.