Abnormalities in quadriceps-hamstring strength. Relationships in polymyositis and dermatomyositis.

Muscle strength determined as torque was measured in patients with dermatomyositis and polymyositis. Patients demonstrated weakness in both quadriceps and hamstring muscle groups. The ratio of quadriceps to hamstring torque (Q:H) was 1.93 +/- 0.38 in controls and 1.60 +/- 0.62 in patients. Patients with Q:H ratios that were below this mean were older, weaker, and were treated with greater doses of prednisone. Fifty-six percent of patients studied initially had low Q:H ratios, and 64% of all patients had low Q:H ratios at some time. The Q:H ratio in patients with steroid and thyroid myopathy, however, was not different than controls. It is hypothesized, therefore, that preferential involvement of the quadriceps group characterizes patients with inflammatory muscle disease.