Figure 4.2 (a)–(d) The patient illustrated had unusually severe bilateral anteromedial OA. Standing, (a) she has marked varus deformities and the radiographs (b) show deep erosions of both medial tibial plateaux. Sitting, (c) the varus corrects. The radiograph (d) shows that this is because in flexion the medial condyles roll out of the anteromedial erosions on to the intact articular surfaces posteriorly.
Figure 4.2 (e) –(i) Because the varus corrected every time the knees were flexed, structural shortening of the medial collateral ligament could not occur. Therefore, with the knees flexed a little, the patient could correct the varus with her own muscles (e). On the radiographs (f), the varus is corrected by applied valgus force. The intraoperative picture (g) shows the anatomical features of anteromedial OA. Note the intact ACL. (Reproduced with permission and copyright © of the British Editorial Society of Bone and Joint Surgery [White SH, Ludkowski PF, Goodfellow JW. Anteromedial osteoarthritis of the knee. J Bone Joint Surg [Br] 1991; 73-B: 582–6].) (h) & (i) show clinical photographs of the same patient with well functioning knees 23 years after her bilateral Oxford medial knee replacements. The patient died in 2013, aged 100 years.
Principal physical signs
1. Pain in the knee is present on standing and is severe when walking. It is relieved by sitting.
2. With the knee (as near as possible) fully extended, the leg is in varus (5–15°) and the deformity cannot be corrected.
3. With the knee flexed 20° or more, the varus can be corrected.
4. With the knee flexed to 90°, the varus corrects spontaneously.
