Isokinetic, electrophysiologic, and clinical function relationships following tourniquet-aided knee arthrotomy

Few data exist pertaining to the validity of isokinetic muscle function tests, particularly in describing their interrelationships with other common clinical assessments. The purpose of this study was to critically analyze the maximal voluntary knee torque, motor unit activity, range of motion, and gait sequelae in a series of 95 patients who had tourniquet-aided meniscectomy or intra-articular loose-body removal. Prior to arthrotomy, affected and contralateral knee data differed minimally. In the first days following arthrotomy, the patients invariably demonstrated severe gait and muscle mechanical impairments, with grossly abnormal quadriceps femoris muscle motor unit activity. Of 32 patients consenting to one-month postoperative diagnostic electromyographic and nerve conduction velocity testing, 17 (53%) were found to have femoral neuropathies, with 8 of the 17 having other thigh and leg neuropathies as well. Patients with neuropathy recovered more slowly and scored significantly lower on functional and electrophysiological measures than patients without neuropathy. One month postarthrotomy, knee extensor torques, motor unit activity, and gait scores averaged about half the normal values, and knee flexion torques and ROM were about 75% of normal. Isokinetic device measurements were moderately related to other clinical measures of postarthrotomy outcome (.58 less than r less than .80). Knee torque measurements alone do not adequately characterize functional capacity.