Symptoms of Perthes Disease
The age of onset, severity, duration, and associated complications of Legg-Calvé-Perthes disease vary greatly from one person to another. Generally, the onset is slow and the progression is gradual. The disorder usually affects children between the ages of eight and ten years, with some instances occurring as early as age two or as late as age 12. The disease typically affects one leg (unilateral); however, in approximately 10% of cases, the condition may subsequently develop in the other leg (bilateral).

In most children, the first symptom is a limp with or without pain. Affected children may experience pain in the hip, knee, thigh, and/or groin. In some cases, the pain may be limited (localized) to the knee or inner part of the thigh. In addition, affected children may also experience muscle spasms of the legs; loss of muscle mass (atrophy) of the front thigh muscles; limited or restricted movements of the hips; and/or inflammation of the membrane lining the hip joint (synovitis). As affected children age, they may also exhibit slightly differing lengths of their two legs (leg length discrepancy).

In all cases, blood supply to the capital femoral epiphysis is re-established and degenerative (necrotic) bone is resorbed and rehardens (re-ossifies). This occurs without therapeutic intervention (spontaneously). The regenerated bone may be only slightly abnormal, misshapen, or significantly misshapen (e.g., abnormally flattened or unusually enlarged). In almost all cases, some shortening of the leg occurs, and in more severe cases, the femoral head may be deformed. The length of time between onset of LCPD and new bone formation may be as short as 18 months or as long as four years.

When onset occurs during the ages of four to nine years, it is, depending on treatment, less likely that osteoarthritis will develop later in life than it is in children with onset after the age of 10. Affected individuals who present significant deformity during re-ossification of the capital femoral epiphysis have an increased risk of developing osteoarthritis later in life.