Immobilization leads to early changes in hydrostatic pressure of bone and joint. A study on experimental...

Immobilization of a rabbit leg in extension results in the early development of an aseptic inflammation, synovial effusion and stiffening, and subsequent osteoarthritis of the knee. To study the pathogenesis of this experimental osteoarthritis, the hydrostatic pressures were measured in the knee, and distal metaphysis and diaphysis of the femur, after different periods of immobilization in 28 rabbits and eight control rabbits. A marked rise in pressure was registered early in the femoral metaphysis, diaphysis and especially in the knee. The maximal pressures were found after two days of immobilization in the metaphysis and seven days in the knee. During the next two weeks the pressures decreased slowly towards the normal values. These changes were related to the thickening and stiffening of the knee. The increased pressure in the bone and joint may be an important pathogenetic factor in the experimental osteoarthritis following immobilization. Measurements of the hydrostatic pressure may be a valuable parameter aiding the development of better preventive and curative methods in arthritis and osteoarthritis.