Knee laxity in patients with osteoarthritis and rheumatoid arthritis.

Thirty-four patients with osteoarthritis (OA) and 32 patients with rheumatoid arthritis (RA) were studied to determine the effects of OA and RA on the laxity of the knee joints. Laxity was measured with the Genucom Knee Analysis System. The antero-posterior laxity of the OA and RA knees was greater than the control, normal knees in the early stage, and decreased with the severity of disease in OA, but not in RA. Severe OA and RA were associated with a restricted internal-external rotation at the knee joint compared with the control. Internal-external rotation decreased with worsening of both diseases. Varus-valgus laxity tended to increase slightly with the severity of disease. While the morphological changes of the cruciate ligaments in advanced OA and RA were not statistically different, the laxity of OA-afflicted knees was affected slightly by the severity of the damage to the cruciate ligaments.