Femoral anteversion is a common orthopedic variation describing an inward twist in the thigh bone (femur) that affects leg alignment. This developmental condition alters the relationship between the hip and knee joints. It is a rotational phenomenon where the head and neck of the femur are angled forward relative to the bone’s lower end. Understanding this alignment issue involves examining how the femur’s rotational position influences movement and posture.
Defining Rotational Alignment of the Femur
The femur has a naturally occurring twist called femoral torsion, which measures the angle formed by the femoral neck and the axis of the knee joint. In typical alignment, the femoral neck is rotated slightly forward relative to the shaft; this angle is referred to as anteversion. This normal forward rotation helps the femoral head fit optimally into the hip socket (acetabulum). The average anteversion in a mature skeleton is typically around 15 degrees.
Excessive femoral anteversion occurs when this angle significantly exceeds the average, sometimes reaching 30 degrees or more, causing the entire leg to rotate internally. This inward twist means the hip joint operates best when the leg is turned toward the midline of the body. Conversely, femoral retroversion describes an angle less than 15 degrees, where the neck is angled backward, leading to external rotation. This rotational variation is primarily developmental, often noticed in children as they begin to walk, and it tends to affect both legs equally.
Recognizing Clinical Signs and Symptoms
The most noticeable sign of excessive femoral anteversion is in-toeing, commonly called “pigeon-toeing,” where the feet turn inward during walking. This is a compensatory mechanism; the individual turns the leg inward so the femoral head sits more securely within the hip socket. The severity of the in-toeing often becomes more apparent when the child is tired or running, as the internal rotation of the femur is exaggerated.
Another characteristic sign involves the alignment of the knees, where the kneecaps (patellae) also appear to point inward when the child is standing or walking. This inward rotation is a direct consequence of the femur’s internal twist. Children with this condition often adopt a specific sitting posture, preferring to sit in a “W” position with their knees bent and feet flared out. This position maximizes hip comfort and stability by accommodating the excessive internal rotation.
Methods for Diagnosis and Measurement
Diagnosis begins with a thorough physical examination assessing the hip’s range of motion. A clinician measures the amount of internal and external rotation while the patient lies on their stomach. A key finding suggesting excessive anteversion is a substantial increase in internal rotation, often exceeding 70 degrees, coupled with a corresponding decrease in external rotation.
The most common technique used in the physical exam to estimate torsion is the Ryder’s test (Craig’s test), which determines the angle of the femoral neck relative to the examination table. While the physical exam provides clinical suspicion, imaging studies are necessary to precisely quantify the rotational angle. Specialized computed tomography (CT) scans are the gold standard for accurately measuring the angle of femoral torsion.
Radiographic studies, such as specialized X-rays, can also measure the rotational difference, though they are less precise than CT scans. The final diagnosis integrates clinical observations of in-toeing and altered hip rotation with the objective measurement of the anteversion angle obtained from imaging. This combination helps distinguish excessive anteversion from other causes of in-toeing, such as tibial torsion or metatarsus adductus.
Treatment Options and Long-Term Outlook
Management of excessive femoral anteversion is overwhelmingly non-operative, as the condition often resolves spontaneously with growth. The angle of anteversion typically undergoes natural de-rotation, decreasing to the normal adult range by approximately eight to ten years of age. Therefore, the standard approach is “watchful waiting,” involving regular monitoring of the child’s gait and hip rotation without immediate intervention.
Physical therapy is sometimes recommended to improve muscle strength and flexibility, although there is limited evidence that exercises alone can alter the underlying bony rotational angle. Braces, special shoes, or orthotics are generally ineffective in correcting the twist of the bone and are not recommended for this condition, as they cannot change the inherent anatomical rotation of the femur.
Surgical intervention, known as a derotational osteotomy, is reserved for a small minority of individuals. Surgery is considered when severe anteversion persists significantly past age ten and causes functional limitations, such as tripping or pain. This procedure involves cutting the femur, rotating it into a more normal alignment, and fixing it with a plate and screws. For the vast majority of people, the long-term prognosis is excellent, as the condition either resolves naturally or the body adapts to the rotational variation.