The thigh bone (femur) is connected to the pelvis, where it forms the hip joint, and the knee, where it forms the knee joint.  Starting at the hip joint, the femur has a ball-shaped section that rotates within the hip socket – this is called the femoral head and it is covered with cartilage.  We bear the weight of the body with standing, walking, running and jumping through the femoral head and the top of the hip socket.  Below the femoral head is a transition point called the neck.  The neck is important as the blood supply to the ball enters the bone at this location.  The neck is also frequently injured with a fracture of the hip.  Below the neck is the shaft of the femur.  The shaft is the main portion of the thigh bone, and it is a strong, tube-like structure (like a pipe) that goes all the way down to the knee.  At the knee, the shaft flares out and is covered by cartilage at the end, making up the knee joint.  The relationship between the position of the femoral head/neck and the knee determines how the hip rotates and this is called femoral version (or torsion).  Normal version (or rotation) allows the hip to rotate in or out normally.  Some patients have excessive forward rotation (anteversion) and others have excessive backward rotation (retroversion).  Patients with excessive anteversion tend to sit in the “W position” and have difficulty rotating their legs out (external rotation) or sitting with crossed legs.  Alternatively, patients with excessive retroversion have difficulty rotating their legs in (internal rotation).  Both forms of abnormal rotation can cause impingement and tears of the labrum, especially in conjunction with other forms of hip impingement (cam, pincer etc.).  This rotation should be evaluated during every examination and can be quantified using special CT or MRI scans.  If the abnormal rotation (version) is determined to be a cause of the hip pain, there are non-surgical and surgical options for treatment.