[An analysis of quadriceps muscle force in boys with Osgood-Schlatter disease].

Osgood-Schlatter disease is thought to be a consequence of microavulsions caused by repeated traction on the tibial tuberosity. For determination of the etiologic factor of this disease, concentric and eccentric force of the quadriceps muscle was measured in the unaffected side and compared with that of normal boys and girls, normal men and women, and patients with cruciate ligament injury of the knee. The relation between the maximum force and its angle velocity was approximated and the ratio of the eccentric force to the concentric force was calculated at 90 deg/sec. In the group with Osgood-Schlatter disease, the eccentric force was especially strong and this group had the highest ratio among all groups. This finding suggests that the increased eccentric force in the extensor mechanism of the knee is an etiologic factor in the disease.