In eighty-five growing rabbits one or both hind limbs were temporarily immobilized with the knee in extension but with the hip free and movable. In almost all of the younger rabbits a subluxation, dislocation, or other skeletal deformity (dysplasia) of the hip joint developed. The dysplastic changes observed were typical of those seen in congenital dislocation of the hip in man.
The development of permanent dislocation or dysplasia of the hip in these experiments was dependent on the duration of the immobilization of the knee in extension. If the hamstring muscles were cut either distally or proximally before immobilization of the knee neither dislocation nor obvious dysplasia of the hip developed.
The prolonged tension of the hamstring muscles provoked by keeping the knee joint in extension is assumed to have been the main factor causing the dislocation and dysplasia of the hip joint in these experiments.
The special phenomenon of coxa vara appearing after immobilization of the knee will be described in detail in a separate article.