(See also Overview of Bone Disorders in Children.)
The femur is the thighbone. The capital femoral epiphysis is the head of the femur (the ball in the ball-and-socket of the hip joint). The epiphysis can slip off the end of the femur. The slipping occurs at the growth plate. Growth plates are soft areas of cartilage near the ends of bones from which children's bones grow.
Slipped capital femoral epiphysis usually develops in early adolescence and most commonly affects boys. Obesity is a major risk factor. Many children who develop this disorder in one hip eventually develop it in both hips.
The cause of slipped capital femoral epiphysis is not known. However, the disorder most likely results from a weakening in the growth plate. A weakening in the growth plate can result from injury, hip deformities, complications due to obesity, inflammation, or changes in levels of hormones in the blood (such as a low thyroid hormone level), which normally occur around puberty (see Puberty in Girls and see Puberty in Boys). The separation causes the top part of the thighbone to eventually lose its blood supply, decay, and collapse.
The first symptom of slipped capital femoral epiphysis may be stiffness or mild pain in the hip. However, the pain may seem to come from the knee or thigh. The pain lessens with rest and worsens with walking or moving the hip. Later, a limp develops, followed by hip pain that extends down the inner thigh to the knee. The affected leg is usually twisted outward.
X-rays are taken of both hips. X-rays of the affected hip show slippage or separation of the head of the thighbone from the rest of the bone.