Pathological changes in this angle result in abnormal posture of the leg: a small angle produces coxa vara and a large angle coxa valga; the latter is usually combined with genu varum, and coxa vara leads genu valgum. Additionally, a line drawn through the femoral neck superimposed on a line drawn through the femoral condyles forms an angle, the torsion angle, which makes it possible for flexion movements of the hip joint to be transposed into rotary movements of the femoral head. Abnormally increased torsion angles result in a limb turned inward and a decreased angle in a limb turned outward; both cases resulting in a reduced range of a persons mobility. Muscles
Hip
There are several ways of classifying the muscles of the hip:

By location or innervation (ventral and dorsal divisions of the plexus layer);
By development on the basis of their points of insertion (a posterior group in two layers and an anterior group); and
By function (i.e. extensors, flexors, adductors, and abductors).Some hip muscles also act either on the knee joint or on vertebral joints. Additionally, because the areas of origin and insertion of many of these muscles are very extensive, these muscles are often involved in several very different movements.
Stabilization exercises like the BOSU ball squat are also important especially as they assist in the ankles having to adjust to the balls form in order to balance. Clinical significance
Lower leg injury
Lower leg injuries are common while running or playing sports. About 10% of all injuries in athletes involve the lower extremities. The majority of athletes sprain their ankles; this is mainly caused by the increased loads onto the feet when they move into the foot down or in an outer ankle position. All areas of the foot, which are the forefoot, midfoot, and rearfoot, absorb various forces while running and this can also lead to injuries. Running and various activities can cause stress fractures, tendinitis, musculotendinous injuries, or any chronic pain to our lower extremities such as the tibia. Types of activities
Injuries to quadriceps or hamstrings are caused by the constant impact loads to the legs during activities, such as kicking a ball. While doing this type of motion, 85% of that shock is absorbed to the hamstrings; this can cause strain to those muscles. Jumping – is another risk because if the legs do not land properly after an initial jump, there may be damage to the meniscus in the knees, sprain to the ankle by everting or inverting the foot, or damage to the Achilles tendon and gastrocnemius if there is too much force while plantar flexing.