Based on what you've told us, it sounds like your daughter may have a problem called slipped capital femoral epiphysis (SCFE). The capital femoral epiphysis is a growth plate at the top of the femur (thighbone).

The epiphysis is made up of cartilage until the bone stops growing. Then it hardens and becomes part of the bone. If shear forces are strong enough, this cap of cartilage can actually slip off the top of the bone.

According to data from the studies done so far, SCFE occurs as a result of obesity. If a girl is overweight, she has an increased risk of developing SCFE. Most cases begin around age 12 but this condition can occur as early as nine years old or as late as 16.

Racial differences may have more to do with socioeconomic factors than ethnicity. Since obesity is linked with SCFE, then poor diet associated with low income may be a key factor. Other factors may be at play in cases of SCFE in normal weight or underweight children.