Femoral retroversion is a rotational or torsional deformity where the thigh bone, or femur, has an abnormal backward twist along its axis. This condition affects the entire alignment of the lower limb, causing the knee and foot to turn outward relative to the hip joint. The misalignment shifts the biomechanical forces across the hip and knee, often resulting in compensatory movement patterns. This structural variation can lead to pain and functional limitations.
Understanding the Anatomy of the Femoral Neck Angle
The normal orientation of the femur involves a slight forward twist of the femoral neck relative to the knee, a condition known as femoral anteversion. This angle, measured between the axis of the femoral neck and the axis of the knee joint, determines the hip’s rotational alignment. In healthy adults, the average femoral anteversion falls within a range of approximately 8 to 15 degrees.
Femoral retroversion describes the opposite structural variation, where this angle is significantly lower than the normal range, or even reversed backward, often indicated by a negative value. The degree of twist dictates how the ball of the femur sits within the hip socket. The natural forward twist of anteversion ensures the femoral head is optimally covered and contained within the acetabulum when the knee and foot are pointing straight ahead.
In retroversion, the backward twist means the femoral head is not optimally aligned when the lower leg is pointing forward. To achieve proper joint congruence and stability, the entire leg must rotate externally.
Why Femoral Retroversion Develops
Femoral retroversion is primarily a developmental or congenital condition, meaning the rotational difference forms before or during early childhood growth. The exact cause is often unclear, but it is believed to be multifactorial, involving a combination of genetics and mechanical forces during development. It frequently runs in families, suggesting a hereditary component.
The position of the fetus within the womb, known as in utero forces, is thought to play a role in the initial torsional alignment of the femur. While most children are born with a high degree of femoral anteversion that gradually self-corrects as they grow and begin to walk, those with retroversion do not experience this normal developmental derotation. This lack of correction results in the persistent backward twist seen in the adult form. In rare instances, retroversion can develop later in life following a severe trauma, such as a femur fracture that heals in an improperly rotated position, known as malunion.
How Retroversion Affects Movement and Causes Pain
The structural misalignment of femoral retroversion forces the hip joint to compensate to maintain a stable connection between the ball and socket. Since the femoral neck is twisted backward, the individual must externally rotate their entire leg to seat the femoral head correctly within the hip socket. This necessary compensatory rotation results in the classic “out-toeing” or “duck-footed” gait pattern, where the feet point outward during walking.
Clinically, a physical examination of a person with retroversion will reveal a significantly limited range of internal hip rotation and a greater-than-normal range of external rotation. This difference in rotational capacity is a diagnostic sign that reflects the underlying bony twist. The altered biomechanics place abnormal stress on surrounding joints and soft tissues, leading to common pain referral patterns.
Many individuals experience hip or groin pain due to the abnormal contact forces within the joint, which can contribute to conditions like femoroacetabular impingement. Additionally, the altered alignment can strain the knee and ankle, causing pain in those areas, such as patellofemoral pain syndrome. Imaging techniques, particularly computed tomography (CT) scans, are used to accurately measure the degree of femoral torsion and confirm the diagnosis.
Treatment Approaches for Femoral Retroversion
Management of femoral retroversion depends on the patient’s age, the severity of symptoms, and the degree of the rotational deformity. In children, mild cases are often managed with observation, as some spontaneous correction may occur during growth. For older patients with mild symptoms, conservative management, focusing on physical therapy, is usually the first step.
Physical therapy aims to strengthen the muscles surrounding the hip and knee to improve stability and address any compensatory muscle imbalances that have developed. This approach can help manage pain and improve function without altering the underlying bone structure. However, if the rotational deformity is severe and causes significant functional impairment, chronic pain, or progressive joint damage, surgical correction may be considered.
The definitive surgical procedure for correcting femoral retroversion is a derotational osteotomy. This surgery involves cutting the femur bone, rotating it to a more normal anteversion angle, and then fixing it in the new position with a plate and screws until the bone heals. This realignment procedure is reserved for adolescents and adults whose skeletal structure is mature and whose symptoms have not responded to conservative treatment.