Collinson v G M Kane & Sons Pty Ltd

DETERMINATION OF APPEAL PANEL
CITATION:	Collinson v G M Kane & Sons Pty Ltd [2023] NSWPICMP 2
APPELLANT:	Kevin Collison
RESPONDENT:	G M Kane & Sons Pty Ltd
Appeal Panel
MEMBER:	Marshal Douglas
MEDICAL ASSESSOR:	James Bodel
MEDICAL ASSESSOR:	John Stephenson
DATE OF DECISION:	9 January 2023
CATCHWORDS:	wORKERS cOMPENSATION - Whether deduction of 75% under section 323 of the Workplace Injury Management and Workers Compensation Act 1998 was correct based on the evidence; Held – deduction not appropriate; the deduction to be made under s 323(1) is 50%; Medical Assessment Certificate revoked.

BACKGROUND TO THE APPLICATION TO APPEAL

On 28 September 2022 Kevin Collinson, the appellant, lodged an Application to Appeal Against the Decision of a Medical Assessor. The medical dispute was assessed by Dr Todd Gotthelf, a Medical Assessor.
The medical dispute that the President of the Personal Injury Commission (Commission), through his delegate, referred to the Medical Assessor to assess related to the degree of permanent impairment the appellant had from an injury he suffered to his right knee on 1 July 2019 while working for G M Kane & Sons Pty Ltd, the respondent.
The medical dispute referred to the Medical Assessor was described in the referral in these terms:
“MEDICAL DISPUTE REFERRED FOR ASSESSMENT (s319 WIM Act)
 the degree of permanent impairment of the worker as a result of an injury
(s319(c))
 whether any proportion of permanent impairment is due to any previous injury
or pre-existing condition or abnormality, and the extent of that proportion
(s319(d))
 whether impairment is permanent (s319(f))
 whether the degree of permanent impairment of the injured worker is fully
ascertainable (s319(g))
Date of Injury: 1 July 2019
Body part/s referred: Right lower extremity
Method of assessment: Whole Person Impairment”
Medical Assessor Gotthelf issued a Medical Assessment Certificate (MAC) on 31 August 2022 in response to that referral, in which he certified that the appellant had 10% whole person impairment (WPI) from his injury. In a table appended to the MAC he set out the specific components of how he computed the appellant’s WPI. That table was in the following form:

Body Part or system

Date of Injury

Chapter,

page and paragraph number in WorkCover Guides

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

% WPI

WPI deductions pursuant to S323 for pre-existing injury, abnormality or condition (expressed as a fraction)

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

Right lower extremity

1/07/19

17-35

17-33

30

2/3

10

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

10%

The appellant’s appeal relates to the deduction of two-thirds the Medical Assessor made under s 323 of the Workplace Injury Management and Workers Compensation Act 1998 (1998 Act). The appellant’s appeal is based on the grounds for appeal provided in s 327(3)(c) and (d) of the 1998 Act, being, respectively, that the assessment was made on the basis of incorrect criteria and that the MAC contains a demonstrable error.
A delegate of the President was satisfied that, on the face of the appellant’s application, at least one ground for appeal has been made out. Accordingly, the appeal proceeded to the Appeal Panel to hear.
The WorkCover Medical Assessment Guidelines 2006 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 the WorkCover Medical Assessment Guidelines 2006. 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.

RELEVANT FACTUAL BACKGROUND

The appellant commenced employment as a truck driver with the respondent in 2009. At the time he suffered his injury on 1 July 2019 he was driving semi-trailers. In a statement he signed on 18 March 2020 he said that at the time he started employment with the respondent he did not have any problems with his right knee. He had however suffered a previous injury to his right knee in 1992 whilst working as a factory worker. That injury involved a dislocation of knee, a rupture of his anterior cruciate ligament and torn meniscus. He underwent a right knee ACL reconstruction and meniscectomy to treat that injury.
The appellant’s solicitors arranged for the appellant to be examined by orthopaedic surgeon Dr Zbigniew Poplawski on 19 February 2020. In a report of that date to the appellant’s solicitors Dr Poplawski set out the history he had obtained from the appellant which included the appellant stating “categorically” that following rehabilitation for his ACL reconstruction he had no problems with his knee until the injury on 1 July 2019. The history Dr Poplawski obtained also included that the appellant consulted his general practitioner (GP) following his injury on 1 July 2019 complaining of an increasingly painful and swollen knee. The history included that the appellant’s GP organised an X-ray and MRI scan and referred him to orthopaedic surgeon Dr Viswanathan. Dr Poplawski said in his report that he viewed the
X-ray and MRI scan of the appellant’s right knee done on 25 July 2019 which was reported to reveal advanced medial compartmental degeneration with complete loss of joint spaces associated with subchondral sclerosis and osteophyte formation. Dr Poplawski said that he also noticed that the investigations revealed the prior ACL surgery with internal fixation and a complete rupture of the previous ACL repair.
Dr Poplawski noted in his report that he had been asked by the appellant’s solicitors, “whether the right knee replacement surgery proposed by Dr Viswanathan is related to the injury our client sustained during the course of employment on 1 July 2019?”. which Dr Poplawski replied that the appellant would have required a right total knee replacement at some stage in future. Dr Poplawski also advised that had the appellant not sustained an injury on 1 July 2019 that resulted in a rupture of his reconstructed ACL and “give away episodes” and ongoing pain then in all likelihood the appellant’s symptoms from the event of 1 July 2019 would have settled and allowed the appellant to return to work. Dr Poplawski said that he felt “that his work injury is the main precipitating factor of his continuing symptoms”.
In a further statement the appellant signed on 16 June 2022 he said that Dr Viswanathan performed a total knee replacement in August 2021.
The appellant’s solicitors again organised for the appellant to be examined by Dr Poplawski on 12 July 2021 to assess the appellant’s permanent impairment from his injury. In a report of 13 December 2021 Dr Poplawski advised that he assessed the appellant had 24% WPI from his injury. He explained that he found the appellant had a poor result from his knee replacement surgery and that this correlated with the appellant having an overall 30% WPI, consistent with Table 17-33 of AMA 5. He also said “deducting 20% = 24% WPI”. He did not explain the basis upon which he made the deduction, but the Appeal Panel assumes it was because Dr Poplawski was of the view that the appellant had a pre-existing condition of osteoarthritis in his knee from his earlier injury in 1992 that contributed to his overall impairment.
On 3 February 2022 the appellant’s solicitors wrote to the respondent’s insurer advising them that the appellant claimed compensation of $65,050 for 24% WPI. The appellant’s solicitors advised that the appellant was making that claim “on the basis of Dr Poplawski’s report”. The appellant’s solicitors attached with their correspondence the reports of Dr Poplawski dated 12 July 2021 and 13 December 2021.
The respondent’s lawyers thereupon organised for the appellant to be examined by orthopaedic surgeon Dr Richard Powell on 1 April 2022. In a report of 11 April 2022 Dr Powell advised that he considered the appellant had a fair result from his knee replacement surgery which, in accordance with Table 17-33 of AMA 5, rated 20% WPI. Dr Powell further advised that there was clear evidence of pre-existing pathology in the appellant’s right knee and that the appellant had a history of ongoing intermittent symptoms involving his right knee leading up to his work injury and that investigations performed immediately after the appellant’s work injury demonstrated the presence of well established tricompartmental osteoarthritis. Dr Powell said that “taking all these factors into consideration I would make a deduction of three quarters”. Dr Powell advised he assessed the appellant to have 5% WPI from his injury.
In a letter dated 29 April 2022 the insurer sent to the appellant, it notified him under s 78 of the 1998 Act that it disputed liability for his claim for compensation for 24% WPI from his injury. The insurer advised the appellant this was because his permanent impairment from his injury did not exceed 10% as required by s 66(1) of the Workers Compensation Act 1987 (the 1987 Act) for him to be entitled to compensation for permanent impairment. Within the reasons it advised him for taking that position, it referred Dr Powell’s assessment of his permanent impairment and it is implicit from what it said therein that it relied on Dr Powell’s assessment.
Thereupon the appellant initiated proceedings in the Commission seeking determination of his claim for compensation under s 66 of the 1987 Act for 24% WPI from his injury. The matter was referred to Member Deborah Moore who, with the consent of the parties, remitted the matter to the President so that it could be referred to the Medical Assessor to assess the medical dispute between the parties relating to the appellant’s WPI from his injury. As mentioned above, the Medical Assessor assessed the appellant had 10% WPI from his injury.

PRELIMINARY REVIEW

The Appeal Panel conducted a preliminary review of the original medical assessment in the absence of the parties and in accordance with the WorkCover Medical Assessment Guidelines 2006.
Based on its preliminary review, the Appeal Panel considered it would not need to examine the appellant. This is because the material before the Appeal Panel is sufficient for the Appeal Panel to determine the appeal and to correct a demonstrable error it found was contained within the MAC.
During its preliminary review, the Appeal Panel also considered whether it should receive into evidence a statement the appellant signed on 28 September 2022.
Section 328(3) of the 1998 Act provides that evidence that is fresh evidence or evidence in additional to or in substitution for the evidence received in relation to a medical assessment appealed against may not be given on an appeal by a party unless the evidence was not available to the party before the medical assessment and could not reasonably have been obtained by the party before that medical assessment.
The appellant in his statement of 28 September 2022 detailed:
(a) his recollection of parts of the conversation that occurred between him and the Medical Assessor relating to the history the Medical Assessor obtained from him during the examination, and
(b) the effect his injury in 1992 had on his ability to kneel.
The appellant made no submissions regarding whether the Appeal Panel should receive his statement into evidence, other than that his statement supports his submissions. The respondent submitted that the appellant’s statement is a competing assertion of what occurred during examination and should not be received into evidence because there is no reason not to accept what the Medical Assessor recorded what was told to him by the appellant.
The appellant’s statement is not fresh evidence insofar as it deals with the affect his injury has on his ability to kneel. That is evidence of what was occurring before the assessment and the appellant could have recorded his evidence on that matter in a statement and filed that with the Commission before the assessment. Insofar as the appellant’s statement relates to that matter, the Appeal Panel is unable to accept it into evidence.
The appellant’s statement insofar as it relates to the conversation that occurred during the medical assessment is fresh evidence. Notwithstanding that, the Appeal Panel retains a discretion as to where it ought to receive his statement relating to those matters into evidence.[1]
[1] Lukacevic v Coates Hire Operations Pty Ltd [2011] NSWCA per Handley AJA at [102].
In Lukacevic Hodgson JA stated that:
“a dispute by the worker as to the history set out in the certificate, or the observations made by the AMS, can readily be raised; and it could be raised honestly or dishonestly, on strong or flimsy grounds. Having regard to the matters I have set out, in my opinion it would be reasonable for an [Appeal Panel] not to admit evidence raising such dispute unless that evidence had substantial prima facie probative value, in terms of its particularity, plausibility and/or independent support. Otherwise, simply be raising such a dispute, going to a matter relevant to the correctness of the certificate, a worker could put the [Appeal Panel] in a position where it had to have a further medical examination conducted by one of its members. I do not think this would be in accord with the policy of the WIM Act.”[2]
[2] Lukacevic at [78].
In the Appeal Panel’s view, the appellant’s evidence relating to the conversation that occurred between him and the Medical Assessor is not sufficiently reliable such that the Appeal Panel should receive it into evidence. It would in the Appeal Panel’s view, most likely be a less reliable record of what occurred than the history the Medical Assessor set out in the MAC. The appellant signed his statement approximately a month after the examination and hence recollection of the conversation is provided a significant time after the actual conversation occurred. The Medical Assessor issued the MAC within two weeks of the examination, which is a shorter time. Further the history the Medical Assessor set out in the MAC is likely to have been based on notes he made at the time of examination. By virtue of that alone, it is likely to be a more reliable record of the history that was provided, than what the appellant recounted in his statement. Further, the Appeal Panel notes that it is unable to put what the appellant says in his statement to the Medical Assessor so as to ascertain from the Medical Assessor whether what the appellant says is accurate.
The Appeal Panel consequently exercises its discretion not to receive his statement into evidence.

EVIDENCE

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.

MEDICAL ASSESSMENT CERTIFICATE

As mentioned above, the issue the appellant raises in his Appeal relates to the deduction the Medical Assessor made under s 323(1) of the 1998 Act. Relevant to this, the Medical Assessor noted within the history obtained from the appellant that the injury that the appellant suffered occurred as the appellant was stepping down from a truck and feeling a “pop in his right knee and immediate pain”. The Medical Assessor noted that the appellant had physiotherapy for his injury and wore a brace for a year. The Medical Assessor recorded that the appellant had a right knee replacement in August 2021.
The history the Medical Assessor obtained included the injury that the appellant suffered in 1992 when the appellant dislocated his right knee and ruptured his anterior crucial ligament and suffered a meniscal tear. The Medical Assessor noted that the appellant had surgery for an ACL reconstruction and meniscectomy.
The Medical Assessor extracted in the MAC various parts of the documentary evidence that had been forwarded to him that he felt was of interest. That included a letter from Dr Viswanathan dated 7 August 2019 in which Dr Viswanathan noted that his initial consultation with the appellant was for a twisting injury the appellant suffered after stepping from a truck and in which Dr Viswanathan also noted that the appellant’s X-ray showed advanced tricompartmental arthritis and that his MRI showed a ruptured ACL graft and degenerate tearing of his medial meniscus. The part from that letter that the Medical Assessor extracted from the MAC also included that Dr Viswanathan’s view that the appellant’s surgical was of a knee replacement but the appellant firstly needed to lose some weight.
The Medical Assessor also recorded in the MAC that the appellant bought imaging studies with him to the examination that were not within the documentation that the Commission had forwarded to him, which included an X-ray and MRI scan of the appellant’s right knee done on 27 July 2019. The Medical Assessor noted that those investigations revealed:
“Previous surgery ACL surgery with tunnels seen and screw in proximal tibia. Loss of joint space medial compartment to 1mm. Varus 4 degrees.”
The Medical Assessor considered that the diagnoses based estimates method was the most appropriate method by which to assess the appellant’s degree of permanent impairment from the injury to his right knee given that the appellant had a total knee replacement. The Medical Assessor considered that that appellant had a poor result from that surgery and, in accordance with Table 17-35 of AMA 5, rated the appellant’s impairment as being 75% lower extremity impairment, which converted to 30% WPI.
No challenge is made by either the appellant or the respondent with respect to that assessment.
As indicated earlier, the Medical Assessor considered a portion of the appellant’s permanent impairment relating to his right knee was due to the previous injury the appellant suffered in 1992 and the condition in his knee that ensued from that injury and that that proportion was two-thirds. The Medical Assessor provided the following explanation for that opinion:
“According to the Guidelines 4th edition, section 1.27 and 1.28, page 6, 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. This proportion is known as ‘the deductible portion’ 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.
The following factors are taken into account when considering deductions for pre-existing conditions:
• Mr Collinson sustained a significant right knee injury while working at ICI Films as a Factor worker in 1992. He sustained a dislocation of the right knee with a ruptured anterior cruciate ligament and meniscal tear. He underwent surgery for an ACL reconstruction and meniscectomy. This injury was a significant risk factor for the development of arthritis of the right knee, and I would consider was the main contributing factor to the development of arthritis of the right knee.
• Mr Collinson indicated that the right knee was never normal and he could never kneel on the right knee, indicating that he had ongoing symptoms of the right knee. Mr Collinson admitted to some aching of the right knee usually in winter time.
• Mr Collinson was obese which is also a significant risk factor for the development of knee arthritis. Other risk factors for knee arthritis include advanced age.
• The mechanism of injury sustained on 1 July 2019 was of a minor kind and was described as him stepping down from the truck and feeling pain in the knee. X-rays from 27 July 2019 were reviewed at the time of the assessment, which revealed significant loss of joint space of the medial compartment to a 1mm cartilage interval, and a significant varus knee. There were no acute injuries. Thus, the injury sustained resulted in a exacerbation of preexisting knee arthritis.
• Mr Collinson was treated with conservative treatment and wore a brace for one year.
Surgery for a knee replacement was performed in August 2021. The injury therefore did not result in the need for surgical treatment, and did not result in any worsening pathology, as the arthritis was already severe at the time of the subject injury.
• Mr Collinson indicated that after the injury he was off work and then returned to light duties until December 2019, and then his work with GM Kane and Sons Pty Ltd ceased. Thus, further work duties after the injury were not a factor in any ongoing symptoms and the need for treatment.
Considering the above information, I consider that the presence of arthritis was pre-existing at the time of the subject injury and was significant with advanced arthritis at the time of the injury. The work place injury did not result in significant worsening of the objective pathology. Surgical treatment was not performed at the time of the injury but rather was performed two years later. Thus I consider that the work place injury did not result in a significant aggravation or acceleration of the right knee condition. Rather the need for a total knee replacement was due to the preexisting condition of advanced knee arthritis. The history and documentation indicated that Mr Collinson was capable of work prior to the subject injury and then symptoms became worse after the subject injury. I consider there is justification to apply some impairment to the work place injury. However, I consider that the majority of impairment is attributable to the pre-existing condition. I consider therefore a 2/3 deduction is reasonable.”

The Medical Assessor also, when commenting on Dr Poplawski’s report of 13 December 2021, observed that Dr Poplawski had indicated that “the appellant had no problems with his right knee until the time of injury and had been working for thirty years in the industry since his ACL rupture”. With respect to that the Medical Assessor said the following:
“I agree with this comment. However, the clinical history supports that the significant contributor to the development of knee arthritis was the ACL rupture over twenty years earlier. It is often the case with knee arthritis that knee pain will worsen at some stage in life regardless of injuries, especially when advanced arthritis is present, as was the case with Mr Collinson. The clinical picture of worsening symptoms in the presence of advanced arthritis was expected at this stage in Mr Collinson’s life, regardless of the work place injury. As the injury did not result in any worsening pathology, and surgery was not performed for two years from the date of injury, I consider that the pre-existing condition was a more significant contributor to the need for knee replacement than the work place injury, justifying my reasoning for a more significant deduction than applied by Dr Poplawski.”

SUBMISSIONS

Both parties made written submissions. They are not repeated in full, but have been considered by the Appeal Panel.
In summary, the appellant submitted that the Medical Assessor wrongly focused on the contribution of his employment to his impairment rather than starting from the assumption that his injury and impairment is work related. The appellant submitted that there is no evidence or inadequate to justify a 75% deduction being made under s 323(1) of the 1998 Act for a pre-existing condition and that the Medical Assessor ought to have assumed the deduction was 10% in accordance with s 323(2). The appellant submitted that the Medical Assessor failed to identify the relevant clinical history relating to the deduction the he made.
The appellant submitted that all scans of the appellant’s knee were done after his injury on 1 July 2019 and the appellant further submitted that “there is only limited factual basis to assert that the degenerative changes are ‘pre-existing’”.
The appellant submitted that “the evidence and explanation adopted by the AMS [sic] was inadequate to justify a 75% deduction for a pre-existing condition or any departure from s323(2) of the WIM Act”. The appellant submitted that the Medical Assessor’s “reasoning lacks logic” and that “there was no basis in which it can reasonably be concluded that the s323 deduction should be 2/3”. The appellant noted that he had his total knee replacement surgery occurred on 11 August 2020 and not in August 2021 as the Medical Assessor recorded in the MAC. The appellant submitted that “this error afflicts the AMS’s reasoning”.
The appellant submitted that the “AMS” recorded an incorrect history. The appellant submitted that the Medical Assessor incorrectly assumed the subject incident was minor, and this was a demonstrable error.
In reply, the respondent submitted that the findings the Medical Assessor made with respect to the injury the appellant suffered were open for the Medical Assessor to make. The respondent submitted that the Medical Assessor proceeded correctly on the premise that the appellant’s injury had resulted in an aggravation or acceleration of pre-existing knee arthritis and that a deduction was applicable in light of the significant nature of that pre-existing arthritis. The respondent noted that the Medical Assessor also obtained a history and was aware of the correct mechanism by which the appellant suffered his injury. The respondent submitted the Medical Assessor undertook a comprehensive review of the available clinical documentation.
The respondent submitted that whilst the Medical Assessor did cite the wrong date for the knee replacement surgery, the Medical Assessor nevertheless provided adequate reasons for the contribution that the appellant’s pre-existing condition made towards the appellant’s total knee replacement and consequently the error with respect to the date of surgery did not result in the Medical Assessor’s assessment of the appellant’s impairment being flawed.
The respondent submitted that the Medical Assessor provided a comprehensive outline of the factors that he took into account in making the deduction for the pre-existing condition and that there was adequate evidence to support the deduction that the Medical Assessor made.

FINDINGS AND REASONS

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.
In Campbelltown City Council v Vegan [2006] NSWCA 284 the Court of Appeal held that the Appeal Panel is obliged to give reasons.
The Appeal Panel rejects the appellant’s submission to the effect that because all the scans of his right knee that are in evidence post-dated his injury the Medical Assessor made an error by finding that the degenerative changes in the appellant’s right knee existed at the time of his injury.
The Appeal Panel notes that the earliest of the investigations of the appellant’s right knee that were done after his injury were an X-ray and MRI scan done on 19 July 2019, that is within three weeks of his injury. The Medical Assessor noted these investigations were reported to reveal loss of joint space in the medial compartment to 1mm. The Medical Assessor also noted that Dr Viswanathan in his report of 7 August 2019 noted that the appellant’s X-ray, which would have been the X-ray of 19 July 2019, showed advance tricompartmental arthritis and that the MRI scan showed a ruptured ACL graft and degenerative tear of the medial meniscus.
The evidence clearly establishes that the appellant suffered an injury to his right knee in 1992 in the form of a tear of the meniscus, a dislocation of the knee and a rupture of his ACL.
The only conclusion to be drawn from that evidence and the evidence in the form of investigations done on 19 July 2019 is that at the time the appellant suffered injury on 1 July 2019 he had substantial osteoarthritis in his knee.
The issue in this case is whether the deduction the Medical Assessor made under s 323(1) of the 1998 Act of two-thirds for the extent to which that pre-existing condition in the appellant’s knee contributed to the appellant’s permanent impairment was supported by the evidence.
There are several authorities detailing the approach a Medical Assessor must take when assessing what if any deduction is to be made under s 323(1) of the 1998 Act.[3]
[3] See especially, Cole v Wenaline Pty Ltd [2010] NSWSC 78; Vitaz v Westform (NSW) Pty Ltd [2011] NSWCA 254 (Vitaz), Ryder v Sundance Bakehouse [2015] NSWSC526 (Ryder) and Pereira v Siemens Ltd [2015] NSWSC 1133.
The Medical Assessor must firstly be satisfied that the worker has an impairment from a work injury at the time of assessment. Secondly, a worker’s prior injury or pre-existing condition or abnormality must be identified. Thirdly, it must be determined whether a proportion of a worker’s post-injury impairment is due to that prior injury or pre-existing condition. Lastly, the extent to which a worker’s post-injury impairment is due to the prior injury or pre-existing condition or abnormality must be determined.
The third stage of the process cannot be done based on assumption or hypothesis, but must be done by reference to the evidence. The evidence must be able to demonstrate that a proportion of a worker’s impairment is due to the pre-existing condition or previous injury.[4] The Supreme Court held in Ryder that the pre-existing condition that a worker has or the prior injury the worker has suffered must make a difference to the outcome in order that a worker’s impairment can be found to be due to it. Insofar as it does make a difference, there must be a deduction.
[4] See Drosd v Workers Compensation Nominal Insurer [2016] NSWSC 1053 at [86].
Further, the fourth stage can also not be done by reference to assumption unless the extent to which a deduction is to be made under s 323(1) would be too difficult or costly to determine, because of the absence of medical evidence or some other reason. In that circumstance, the deduction to be made under s 323(1) is be assumed, in accordance with s 323(2) of the 1987 Act, to be 10%. However, s 323(2) makes clear that that assumption cannot be made if it is not at odds with the evidence.
The evidence in this matter demonstrates the appellant was largely untroubled by symptoms in his right knee following his rehabilitation after his ACL was reconstructed in 1992. The evidence demonstrates that he had been working in arduous employment from that time until the date of his injury. Most of his employment within that time involved him driving trucks and in the last three to five years before his injury driving semi-trailers. That would have necessitated him climbing up to the cabin of the truck and climbing down from the cabin of the truck. During this period of time there is no evidence of his suffering any significant symptoms from the degeneration in his knee which at least in the three to five years preceding his injury would have been substantial. The clinical records do not reveal that he sought treatment for knee symptoms in this time. The injury he suffered on 1 July 2019 resulted in his suffering significant and continuous symptoms in his right knee since then. His symptoms were such that within a short time from the injury he was being recommended a knee replacement.
The Medical Assessor’s reasoning for the deduction he made of two-thirds for the proportion that the appellant’s pre-existing condition made to the appellant’s permanent impairment included that the appellant’s injury did not result in the immediate need for surgical treatment, and did not require surgery until two years after the injury. His reasoning was also based on the appellant’s injury not resulting in any worsening of the appellant’s pathology of osteoarthritis that was already existing in the appellant’s knee at the time of injury.
The Appeal Panel considers that the Medical Assessor’s reasoning in this regard is wrong. It is not supported by the evidence. The injury the appellant suffered was a material and substantial contributor to his need for surgery. The surgery was indicated both because the appellant had extensive osteoarthritis in his right knee and also to alleviate the appellant’s symptoms from this arthritis that were precipitated from the injury the appellant suffered to his right knee. The appellant’s surgery occurred approximately one year after his injury and it was recommended for him within five weeks of his having suffered his injury. The fact that the appellant’s injury did not worsen his osteoarthritis, in the sense of not advancing the pathology, is not on point because the injury did precipitate symptoms from the pathology that the appellant was not previously experiencing, such that the appellant required a knee replacement.
The appellant’s impairment is due to him having an artificial right knee. As just discussed, the appellant’s surgery in the form of his knee replacement, by which he obtained his artificial knee, was due to a combination of his having existing and extensive degenerative osteoarthritis in his knee at the time of injury and that condition being rendered symptomatic as a result of his injury.
The Appeal Panel considers, given that, that the Medical Assessor did err by concluding on the evidence that the need for surgery was to treat the osteoarthritis, rather than the symptoms from the injury. In the Appeal Panel’s view the correct conclusion on the evidence is that both the appellant’s osteoarthritis and the injury played equal roles.
In that circumstance, s 323(2) cannot engaged. This is because the evidence establishes that in all likelihood both the appellant’s extensive osteoarthritis and the injury made equal contributions to the appellant’s need for a total right knee replacement and hence the appellant’s permanent impairment, and consequently it is not difficult to determine the proportion of the appellant’s impairment that is due to the pre-existing condition and, in any event, to make an assumption that it would be 10% would be at odds with the available evidence.
Accordingly, the deduction to be made under s 323(1) is 50%.
For these reasons, the Appeal Panel has determined that the MAC issued on 31 August 2022 should be revoked, and a new MAC should be issued. The new certificate is attached to this statement of reasons.

[2023] NSWPICMP 2

9 January 2023