Selective type II fibre muscular atrophy in patients with osteoarthritis of the hip.

The size and the distribution of type I and tye II fibres was determined in the gluteus maximus (21 cases), gluteus medius (56 cases) and tensor faciae latae (27 cases) muscles of patients with osteoarthritis of the hip. The patients were of both sexes, aged between 37 and 64 years (younger group) and between 65 and 78 years (older group). Autopsy material of the two comparable age groups and of a group of "normal" adults (aged 22-44 years) served as controls. It was shown statistically that the diameter of both types of fibres and the relative number of type II fibres diminished with progressing age. In patients with osteoarthritis the degree of the selective atrophy of type II fibres was significantly higher than in the control groups. The atrophy is interpreted as a consequence of diminished muscular activity. No neurogenic lesions were detected either in the muscles of the patients or in those of the control groups.