A Roentgenographic Study of Transitory Synovitis of the Hip Joint

Transitory synovitis of the hip joint, called also intermittent hydrarthrosis (2), has been described (1–9) as a disease entity characterized by the following phenomena: (a) symptoms and physical signs of an arthritis of the hip joint; (b) negative x-ray findings; (c) disappearance of all symptoms and physical signs within a short period. The disease is one of childhood. The main symptom is most frequently pain of sudden onset in the region of the hip joint, with a limp on the affected side, associated with the usual signs of an infection. A history of previous injury has been obtained in some cases. Limitation of movement, especially of abduction internal rotation, and extension, seems to confirm the clinical diagnosis of arthritis of the hip joint. The pathological changes of this condition, which is also called “coxitis serosa,” are to be found within the synovial membrane of the hip joint, and consist in a swelling of the joint capsule following an intra-articular effusion. As for the nature of the effusion and the etiology of the disease, all authors agree that the cause of the condition is “non-specific.” A low-grade infection in combination with allergy has been cited as a causative factor. Edwards (3) aspirated the involved joint on two occasions. The fluid was xanthochromic. No bacteria were present in stains. It is universally agreed that the x-ray findings are always negative. This, however, concerns only changes in bone. When studying the x-ray appearances of the soft tissues, we were able to find changes which were pathognomonic for a swelling of the synovial membrane, which indicates a synovitis. Our findings are based on the fact that a swelling of the synovial membrane is associated with a swelling of the musculature surrounding the joint. Among the muscles which are in direct anatomic relation to the hip joint are three which can easily be recognized in the roentgenogram, the internal obturator, the gluteus minimus, and the ileopsoas. Hefke and Turner (7) described the swelling of the obturator internus as an early x-ray sign of infectious arthritis of the hip joint and called it the “obturator sign.” The muscular swelling can be recognized in the roentgenogram as a broadening of the affected muscles and the disappearance of the intermuscular septum, which normally is more radiolucent than the rest of the muscle. When the diseased side is compared with the healthy one, the muscle edema can be recognized either by a circumscribed swelling or by a disappearance of the normal demarcation line between neighboring muscles (Fig. 1, right side). The normal obturator shadow can be recognized at its origin within the obturator foramen, and its course can be followed into the small pelvis by its slightly S-shaped outline (Fig. 1, left side).