Intracapsular pressure and pain in coxarthrosis

Intracapsular hip pressure was measured before surgery in 17 patients (18 hips) with coxarthrosis. The results were correlated to pain as registered on a visual analog scale. With the hip in extension, the pressure was 49.5 mmHg (SD, 40.2); in 45 degrees of flexion, it was 21.3 mmHg (SD, 14.6); in extension and inward rotation, it was 105.7 mmHg (SD, 76.0); and in extension and outward rotation, it was 40.8 mmHg (SD, 32.0). A small amount, 0.7 mL (SD, 1.14), of joint fluid was aspirated following pressure registration. Pressure correlated significantly to pain at night, when starting to walk, and on walking. It is suggested that the increase in intracapsular hip pressure is a cause of pain in coxarthrosis, with subsequent limitation of movement and joint contracture.