Other linked birth defects include the dislocation or instability of the joint between the femur and the kneecap, a shortened tibia or fibula, and foot deformities.

This deformity is sometimes called congenital short femur, because the child’s anatomy from hip to knee is contiguous and similar to their peers except for the one shortened bone.

This defect is more severe than type A deformities because it will not heal spontaneously and, at skeletal maturity, the proximal femur (lower part near the knee) will not connect with the femoral head.

In fact, many children with type C deformities also have acetabular dysplasia, a condition in which the acetabulum (hip socket) is shallow, abnormally shaped, and oriented outward.

Depending on the severity of the deformities, the treatment may include the amputation of the foot or part of the leg, lengthening of the femur, extension prosthesis, or custom shoe lifts.

In less severe cases, the use of an Ilizarov apparatus can be successful in conjunction with hip and knee surgeries (depending on the status of the femoral head/kneecap) to extend the femur length to normal ranges.