Significance of synovitis in Legg-Calve-Perthes disease

Synovitis is an important feature in Legg-Calve-Perthes disease (LCPD) with a significant prognostically negative impact on clinical symptoms, cartila ge biochemistry, mechanical properties of the cartilage, joint biomechanics , and prognosis toward healing with a congruent, spherical head of femur. S ynovitis causes cartilage edema, deterioration of the cartilage's mechanica l properties, cartilage hypermetabolism, and, subsequently, cartilage hyper trophy. This sequence of events could explain the clinical course, which co nsists of cartilage hypertrophy, lateral subluxation, anterolateral deforma tion of the head, and, subsequently, joint incongruence in prognostically p oor cases of LCPD. A factor in the deformation of the hypertrophic cartilag e of the epiphysis is decreased range of motion of the hip, because of pain caused by the increase in intracapsular pressure and the subsequent decrea se in the "molding" ability of the acetabulum. Synovitis in LCPD causes an increased intracapsular pressure, the magnitude of which may, in some patie nts, intermittently compromise the blood supply to the proximal femoral epi physis. Whether synovitis is the consequence of, or precedes, the loss of b lood supply and epiphyseal necrosis is not yet established. Significant and persistent synovitis during the entire course of the disease emphasizes th e importance of magnetic resonance imaging as the method of choice for the diagnosis and the prognosis, as well as the monitoring of therapy. The prog nostically negative effects of synovitis suggest that more therapeutic effo rts should be focused on the treatment of synovitis, from a palliative and prognostic point of view.