Muscle mass, isokinetic torque, and functional capacity in women with osteoarthritis of the knee.

OBJECTIVES: To investigate the relations between cross-sectional area and concentric and eccentric torques in the quadriceps and hamstring muscles and to determine how functional capacity relates to pain, muscle mass, and concentric and eccentric knee torques in women who have bilateral osteoarthritis (OA) of the knee.
DESIGN: Randomized, descriptive study.
SETTING: A university exercise physiology laboratory in Turkey. PARTICIPANTS: Eighteen women with bilateral knee OA (grades 2 or 3) graded radiographically.
INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Selected functional tests included the 15-m walk, rising from a chair, descending stairs, and stair climbing. Pain during the functional tests was subjectively measured on an 11-point scale (range, 0-10). Concentric and eccentric torques of the quadriceps and hamstring muscles were measured by isokinetic dynamometry with angular velocities of 60 degrees, 120 degrees, and 180 degrees /s; cross-sectional areas of the quadriceps and hamstring muscles were measured by computed tomography.
RESULTS: Eccentric torque was significantly (P range, <.05 to.001) greater than concentric torque for the quadriceps (range, 16%-100%) and hamstring (range, 50%-158%) muscles at all angular velocities. Torque-velocity curves for concentric and eccentric contractions were almost identical to those found in healthy young and elderly people. According to r(2) values, cross-sectional area of the quadriceps and hamstring muscles explained 24% to 61% (r(2) range,.24-.61) and 38% to 51% (r(2) range,.38-.51) of the variations in concentric and eccentric peak torques, respectively. Very small to moderate correlations (.01-.75) were observed among torque at any velocity and the variables of functional capacity and pain. For stair-climbing times, the best predictor variable was the eccentric hamstring to concentric quadriceps torque ratio. For stair descending, it was the concentric hamstring to eccentric quadriceps torque ratios. These torque ratios explained 81% (r(2)=.81) and 61% (r(2)=.61) of the variations, respectively.
CONCLUSIONS: The findings in a patient group with bilateral OA of the knee showed that (1) eccentric torque is greater than concentric torque in knee muscles; (2) the correlation coefficients (r) between concentric and eccentric torques at different velocities (r range,.63-.86), but not between reciprocal torque ratios (r range,.02-.69), are good; (3) cross-sectional area cannot be considered as a single predictor of peak torque for either quadriceps or hamstring muscles; and (4) the variation in descending stairs and stair-climbing capacities can be explained by the reciprocal torque ratios of knee muscles.