Clearly enough she was not giving an account of her medical retirement that treated the knee as other than central to it.
35 And earlier in examination in chief the Respondent gave a much fuller account why she had had to give up work which reinforces that centrality. A fair reading of that evidence shows that she attributes her medical retirement to disability in performing her nursing functions stemming from pain and restricted movement which she experienced with her knee. These were precisely the trial judge's findings (Red Book, 35 F to I). Thus after the twisting injury she went back to work on restricted duties, limited initially to paper work. She then progressed to night duty soon interspersed with day duty. She explains that she suffered a lot more pain in her knee than immediately after the second arthroscopy (Combined Appeal Book, 11 W to 12 E). She could not carry out functions such as wiping the patients' bottoms when they were sitting on colludes and lifting anything that was low on the ground and the nurses had to help her (Combined Appeal Book, 12 P-T and again 14M-V). She was eventually flown down to Sydney where Health Quest "suggested medical retirement because of my condition", meaning the condition she had previously described; see Combined Appeal Book, 12 Y-13 E)
36 She gave evidence that the worse her knee was the worse her back was. Thus Combined Appeal Book, 13 W-14 H:
"Q. Let me ask you about something else. At some point did you have any pain in your back?
A. Yes.
Q. When did you first get that?
A. About six months before I finished work I started to get muscle spasms in my back and I went to Dr Perry and he gave me Valium which didn't help a lot and when my knee was really playing up my back was really tight.
Q. Was this the situation that the worse your knee was the worse your back was?
A. Yes.
Q. Is that still the situation now?
A. Yes.
Q. Prior to that first onset which I think would've been about March/April 97, about six months before you finished work, had you had any back problems?
A. No."
37 That provides context for the cross-examination so strongly relied upon by the Appellant quoted in para 23 above. It becomes quite clear both from that context and from the use of the word "immediate" before "cause" in the passage itself as well as the later reference to "immediately" that the evidence given by the Respondent certainly did not preclude a finding that her knee remained the operative or substantive cause of her ceasing permanently to work. Rather the pulling incident relating to her back simply precipitated her contacting her work supervisors to say that she was "unable to continue to work" (Combined Appeal Book, 28D). That, it should be remembered, did not lead then and there to medical retirement, but to her twenty-one day sick leave. It was not till a month later (24 November 1997) that her employment actually terminated following Dr Gapper's report of 13 November 1997. If the Appellant wanted to rely on the Respondent's evidence as a concession that the real cause of her medical retirement was her back problems exacerbated by the pulling incident and wholly independent of any effect of the fall, that in fairness should have been put to her squarely. It was not.
38 I understand the trial judge to be saying, albeit with some understandable imprecision, that the lower back symptoms firstly of March or April 1997 were not "a material cause" of her ceasing her employment in October 1997.
39 By necessary implication, the trial judge is to be understood as saying that back symptoms generally, and thus also those which followed the pulling incident, were not "a" material cause of the medical retirement either; I interpolate that they may well have precipitated her taking sick leave but should not be considered the sufficient cause of her medical retirement. It might have been clearer had the trial judge in rejecting those circumstances as a material cause used the definite article "the" instead in conveying rejection of those circumstances as being sufficient in themselves and irrespective of the Appellant's negligence, to bring about medical retirement. Clearly enough use of that expression "the material cause" of medical retirement in the following sentence where he refers to the pain, discomfort, etc. following the fall, indicates that he saw those rather as the operative cause. That was a conclusion properly open to him on the medical evidence as well as the Respondent's own account.
40 I should interpose here that terminological inexactitude about causation is not uncommon in negligence cases. It simply reflects that causation in the law is not a matter of scientific precision. It has been said often enough that causation is a question of fact, to be resolved as a matter of common sense, by reference to the correct legal principles operating in the particular context and where policy issues play a now acknowledged part; see for example Bennett v Minister for Community Welfare (1992) 176 CLR 408. What the trial judge was really doing was explaining what happened in a commonsense way, just as authority requires; see the discussion on this in Jane Stapleton "Perspectives on Causation" in Oxford Essays in Jurisprudence (OUP, 1999).
41 The trial judge relied substantially on the Appellant's own account. The Appellant's own account is important for two reasons. First, the Respondent is the best witness of her own symptoms, including experience of pain. Second, she can express her attitude to her continued working, and the trial judge assess its genuineness. It was an attitude which the trial judge described as stoical (Red Book, 35U). It is for these reasons that the trial judge would have derived some advantage from seeing the witness. I should add that it might have been preferable had the conflicting medical evidence been tested by some limited cross-examination. Of course this was not primarily a decision for the judge but the parties. Nonetheless issues such as the extent the back condition was affected by the knee might have been probed. In saying this, I make no criticism of the trial judge, who is largely in the hands of the parties and operates with a busy list.
42 This appeal has proceeded on the basis that neither party challenged the trial judge's earlier finding that he was not satisfied that the lower back symptoms were causally connected with the fall. That too was a conclusion open to the trial judge, who in that regard did not accept Dr Searle's evidence though he did accept it as to the right knee. As to the latter the trial judge confirms that he does accept the following quoted passage from Dr Searle's report of 1 July 1998: "the injury suffered in the accident materially contributed to her being unable to continue with her employment as a nurse as and from the actual date of cessation of her employment"; see Red Book, 35 O-R and Combined Appeal Book, 215D-F).
43 The medical evidence further supports the trial judge's rejection of the lower back symptoms as the operative cause of her ceasing employment. Thus the Respondent had never complained of back pain in isolation before its exacerbation in October 1997 from the pulling incident. The sick leave record (Combined Appeal Book, 60) shows that there was no time off for back pain prior to October 1997. Three periods of 9, 10 and 2 days off in October and November 1997 were all for back pain "related to knee injury"; see Combined Appeal Book, 61 K-M.
44 Moreover, the history of back pain was minor compared to the knee. Thus Dr Opie in a report dated 16 March 1998 recorded, "back pain is now intermittent and mainly comes when the knee pain is severe" (Combined Appeal Book, 106 P). He noted, "right knee pain", "right knee swelling", and "minor low back pain". That in turn explains his conclusion that "back pain and right knee pain contributed to her invalidity and made her incapable of full-time work"; see Combined Appeal Book, 109. The evidence of the Respondent was that when her knee was worse her back was worse; see Combined Appeal Book, 13 Y-14 F.
45 Significantly in the Health Quest report which finally led to her medical retirement, dated 13 November 1997, the history of knee problems is set out (Combined Appeal Book, 197 P-R). Significantly, the report refers to a combination of lower back pain and right knee problems (Combined Appeal Book, 197S).
46 Finally, the risk that the back (or indeed her pre-existing arthritic knee) might have caused the Plaintiff problems anyway is fully and adequately catered for in the heavy discount the trial judge imposed on future economic loss. In so doing, he had basis in authority: see for example the judgment of Windeyer J in Faulkner v Keffalinos (1971) 45 ALJR 80 at 85-6. While her residual earning capacity may have been the reason for the first element of discount, namely reducing her working age from 65 to 60 and her net weekly earnings from $650 per week to $400 per week, clearly increasing the percentage for the usual vicissitudes of life from 15% to 25% was directed to "her pre-existing problems". I am satisfied that I may infer that these would have included not only the arthritic condition in her knee but also her as yet symptomless back problem at the time of the accident; see Red Book, 37 M-38 D. Indeed the reduction in her working age is also recognition of these factors.
47 The foregoing analysis of the evidence disposes of any appeal based on there being either insufficient reasons or failure to consider relevant matters or finding against the evidence and weight of evidence in relation to the Respondent's back condition. Moreover, the trial judge's approach to the back condition as also to the pre-existing knee condition is in accordance with the principles applicable to pre-existing conditions to which I now turn.