We studied the musculature of the lower extremity in forty-one patients
with chronic symptomatic instability of the anterior cruciate ligament.
Computed tomographic and clinical measurements of the limb were taken at
levels fifteen and twenty-five centimeters proximal to the medial joint
line and ten centimeters distal to it. Biopsy specimens from the vastus
lateralis of both lower extremities were analyzed by histochemistry and
electron microscopy. Computed tomography revealed a decrease in the muscle
square area of the affected thigh of 8 per cent as compared with the
control lower extremity. There was quadriceps atrophy of 10 per cent and
hamstrings atrophy of only 4 per cent. The atrophy of the vastus medialis
was significantly greater than that of the entire quadriceps.
Histochemistry revealed a similar decrease in fiber size for all fiber
types, and hence no shift in fiber type. Electron microscopy showed an
increase in intracellular fat but no change in mitochondrial volume density
or capillarization.