Muscle strength.
Isometric hip abduction and knee extension strength (force-generating capacity) was assessed bilaterally with a Nicholas Manual Muscle Tester (model 01160)*according to the protocol of Bohannon.23 The hip abductors were chosen because some data have suggested that stronger hip abductors may assist in reducing the knee adduction moment.24 The quadriceps femoris muscles were assessed because knee extensor strength has been correlated with both pain severity and physical function in knee OA.25–27 The peak strength of each muscle group was assessed 3 times, and the highest score was recorded (in kilograms).Handheld dynamometry demonstrated adequate test-retest reliability for the muscles of the lower limbs in a community-dwelling group of
older people (intraclass correlation coefficients [ICCs] .95–1.00).28