Isokinetic and isometric testing of knee musculature in patients with rheumatoid arthritis with mild knee involvement.

This study sought to determine if weakness and poor endurance of quadriceps and hamstring muscles are present in rheumatoid arthritis (RA) patients with minimally involved knees; determine if there is an abnormal hamstring/quadriceps ratio or abnormal torque curves in RA patients; and begin to evaluate the feasibility of isokinetic (IK) exercise in RA patients. Sixteen RA patients with minimally involved knees and 16 matched control subjects were tested bilaterally with a Cybex II dynamometer. Torque values in the RA group were significantly less (78% for isokinetic and 81% for isometric). The hamstring/quadriceps torque ratio was significantly higher in the RA patients than in the controls: 66.8% vs 61.7%. There was no significant difference in endurance between the two groups. In the RA patients the angle at which peak torque occurred shifted later in the range of motion (37.4 degrees) compared with the control subjects (28.7 degrees). Except for IK torque of hamstring muscles in the control group, there was no significant difference in the torque values between the right and left sides in RA patients or control subjects. The findings suggested that even in RA patients with minimally involved joints, muscle weakness was present; exercise of quadriceps should be emphasized since in RA patients quadriceps were weaker than hamstrings; and isokinetic testing is feasible in selected patients with RA.