We set up a trial to test whether the KT1000 arthrometer would give consistent measurements of anteroposterior laxity when used by the same and different examiners on the knees of the same subjects on the same day. The results showed substantial inter- and intra-examiner variation in the measurements both of absolute displacement in single knees and of side-to-side differences between pairs of knees. This casts doubt on the reliability of the instrument when used to compare the results of different techniques for reconstructing injured cruciate ligaments.

One of the objectives of knee replacement is to correct flexion deformity, the frequent consequence of rheumatoid arthritis and osteoarthritis. A review of 697 primary and revision replacements carried out between 1969 and 1985 and followed up from 1 to 16 years found that such deformity was present in 61% of knees before the primary operation. Replacement reduced this to 17% and the improvement was usually maintained. The deformity was present in only 21% of the replacements which required revision and the second operation reduced this to 8%. Flexion contractures affected rheumatoid knees more often and more seriously than osteoarthritic knees, but arthroplasty was more successful in correcting the deformity in the former. All of the 11 types of prosthesis used achieved some degree of correction, but the Walldius hinge and the variants of the Freeman condylar design were the most successful. Surprisingly, the best outcome, in terms of pain and reduced need for revision, was found in the rheumatoid knees most seriously deformed before operation, but this association was absent in the osteoarthritic knees. Postoperative deformity in knees without pain or extreme weakness did not appear to influence the patients' ability to walk or to use stairs or a chair, as measured by unexacting tests in the clinic.

Many knee replacement prostheses, embodying various principles of design, are now available and there is need for a method by which valid comparisons of results can be made. An important criterion of success is durability, so the length of time the prostheses have been in situ must be taken into account. Such a method is proposed here and is applied to the results of 673 knee replacements, of nine different types, implanted at the same hospital between 1970 and 1983. A prosthesis was considered to have failed if it had been removed or persistently caused severe pain. Two types of prosthesis were found to be significantly less successful than the other seven, between which none consistently showed significant superiority. Results for the seven types were similar despite the facts that they had been used for knees with different degrees of damage, some as secondary implants, and that they were of different design and at different stages of technical development. The more recently introduced types of prosthesis, designed to have theoretical advantages, were found in practice to be no more successful than the models they superseded.

Experiments have been performed on rabbits and sheep which demonstrate that pure carbon, in a flexible and filamentous form of great strength, can be used successfully to induce the formation of new tendons. A concept fundamentally different from that underlying the use of other artificial tendon replacements is involved, in which rapidly developing tendon-like tissue is induced to form around the implant. This gradually takes over the function of the implant. The early results in rabbits and the late results in sheep suggest that filamentous carbon may have a place in the replacement of the calcaneal tendon and the collateral ligaments of the knee.