KNEE LAXITY IN SYMPTOMATIC OSTEOARTHRITIS

Twenty-two patients with primary osteoarthritis (OA) of the knee were studied to determine the effects of OA on laxity of the knee Joint. La xity was measured with a Genucom Knee Analysis System. Ten knees had m ild OA (> 50% preservation of joint space). Fifteen knees had moderate OA (some preservation of joint space, but < 50%). Eighteen knees had severe OA (no joint space). A group of 18 knees from 9 healthy (asympt omatic) subjects of ages similar to those of the OA patients were used as controls. Compared to control knees, severe OA knees had less tota l anteroposterior (AP) translation (12.2 versus 6.6 mm, p < 0.025) and less total tibial rotation (79 versus 59 degrees, p < 0.01). Compared to early OA knees, knees with severe OA had 57% less average total AP translation (15.2 versus 6.6 mm, p < 0.01), 31% less total varus/valg us rotation (15 degrees versus 10.4 degrees, p < 0.016), and 26% less total internal/external tibial rotation (80.1 degrees versus 59 degree s, p < 0.007). These data indicate that osteoarthritic knees tend to h ave less laxity than normal knees, probably because of a combination o f contracture of the ligaments and pressure of osteophytes against lig aments and other capsular structures.