Muscles laterally rotating the hip joint

Gluteus maximus

Piriformis

Obturator internus

Gemellus superior

Gemelus inferior

Quadratus femoris

Obturator externus

Piriformis

Piriformis is found posterior to the hip joint, being in the same plane as gluteus medius. It is triangular in shape, with its base in the pelvis and apex in the gluteal region.

Its upper attachment is to the front of the second to fourth sacral segments, coming between and lateral to the anterior sacral foramina. It has an additional attachment from the gluteal surface of the ilium and the pelvic surface of the sacrotuberous ligament as it passes out of the pelvis through the greater sciatic foramen into the gluteal region. Its fibres continue to pass downwards, laterally and forwards, narrowing into a tendon which attaches to the upper border and medial side of the greater trochanter of the femur. The fibres run in a straight line from the origin to the insertion through the greater sciatic foramen.

Nerve supply

Piriformis is supplied from the anterior rami of the sacral plexus, L5, S1, 2; and mainly S1. The skin covering this area is supplied by the same nerve roots but it must be remembered that this is a deep muscle and the gluteus maximus intervenes between the two.

Action

In the anatomical position this muscle will certainly be a lateral rotator of the thigh, although it is situated a little high. However, in the sitting position it is concerned in the important action of the abduction, and in this particular situation is well positioned for this action. It is an important muscle in holding the head of the femur in the acetabulum.

Functional activity

It is well to remember that many times we only consider the action of a muscle in the anatomical position. In the sitting position, the pull of muscles changes and the movement produced may bear little or no relation to the previous action. Piriformis will be particularly concerned in the following activities:

1. abduction when sitting, for example in moving from one chair to another without standing up;
2. moving the legs to the outside of a car in preparation for standing up;
3. stabilizing the pelvis when the trunk is rotated;
4. controlling the balance of the pelvis when standing on a moving bus.

It is not therefore surprising that strain of this muscle is quite common, but unfortunately easily overlooked.

Palpation

This is not easy as piriformis is situated deep inside the buttock. Dig your fingers into the buttock just lateral to the sacrum and then push the outside of the thigh up against the leg of a table or some such resistance; you can feel then the muscle contract, although it must be remembered that a large part of the muscle is in the pelvis.

 

Obturator internus

Obturator internus is again a triangularly shaped muscle, situated partly in the pelvis and partly in the gluteal region posterior to the hip joint. It arises from the internal surface of the obturator membrane and surrounding bony margin, except at the obturator canal. The bony attachment extends backwards as far as the pelvic surface of the ilium. The muscle fibres pass laterally, but mainly backwards towards the lesser sciatic foramen, through which they pass, narrowing down and becoming tendinous.

As the tendon passes through the lesser sciatic foramen deep to the sacrotuberous ligament it changes direction to the sacrotuberous ligament it changes direction to pass forwards and laterally to insert into the medial surface of the greater trochanter of the femur in front of and above the trochanteric fossa. Before attaching to the femur, the tendon is commonly joined by the tendons of the gemellus superior above, and the gemellus inferior below. Occasionally these two tendons will insert into the greater trochanter above and below the tendon of the obturator internus.

The inner(pelvic) surface of obturator internus is covered by the obturator fascia, from which arises part of levator ani. As the tendon of obturator internus turns around the lesser sciatic notch the surface of the bone in this region is grooved and covered with cartilage. A bursa intervenes between tendon and cartilage.

Nerve supply

This muscle is supplied by the nerve to obturator internus, root value L5, S1, 2. The skin covering this area is mainly supplied by S3.

Action

In the anatomical position this muscle is a lateral rotator of the thigh pulling the greater trochanter backwards using the hip joint as the fulcrum. However, when the hip is flexed to a right angle, it will pull the upper end of the femur medially, and therefore the lower end will move laterally as in abduction.

Functional activity

As in the case of the piriformis, obturator internus will be used when moving sideways in the seated position, in swinging the lower limb sideways, as in placing the limb outside a car, and in balancing and controlling the stability of the trunk when the seated person is being rocked from side to side. For the same reasons, moving around on the floor or on a platform, either sitting or crawling will require considerable activity in this muscle.

Gemellus superior

As obturator internus passes out of the pelvis around the lesser sciatic notch it is joined by gemellus superior and inferior.

Gemellus superior arises from te gluteal surface of the ischial spine. It runs laterally and slightly downwards to blend with the superior aspect of the tendon of the obturator internus. Sometimes its fibres are prolonged onto the medial surface of the greater trochanter of the femur.

Nerve supply

The muscle is supplied by the nerve to obturator internus, root value L5, S1, 2.

Gemellus inferior

Gemellus inferior arises from the upper part of the ischial tuberosity. It runs laterally and slightly upwards to blend with the inferior aspect of the tendon of obturator internus.

Nerve supply

The muscle is supplied by the nerve to quadratus femoris, root value L4, 5, S1.

Action

The gemelli aid obturator internus in its action. As obturator internus turns around the lesser sciatic notch it will lose some of its power; this will obviously be compensated for by the pull of the gemelli.

Quadratus femoris

This muscle is situated below gemellus inferior and above the upper margin of adductor magnus. It is a flat quadrilateral muscle, separated from the hip joint by the obturator externus.

It attaches to the ischial tuberosity just below the lower rim of the acetabulum. The fibres pass laterally to attach to the quadrate tubercle situated half way down the intertrochanteric crest of femur and the area of bone surrounding it.

Nerve supply

The muscle is supplied by the nerve to quadratus femoris, root value L4, 5, S1.

Action

In the anatomical position quadratus femoris is obviously a lateral rotator of the hip joint, but with the hip flexed, it will act as an abductor of the hip.

Obturator externus

This is a triangular muscle having its muscular base attached to the outer surface of the obturator membrane and the surrounding margins of the pubis and ischium, excluding the area superiorly around the obturator canal. The muscle fibres converge on to a tendon which runs in a groove below the acetabulum across the back of the neck of the femur, which it grooves, to insert into the trochanteric fossa of femur. The muscle lies deep to quadratus femoris.

Nerve supply

The muscle is supplied by the posterior branch of the obturator nerve, root value L3, 4.

Action

In the anatomical position obturator externus laterally rotates the femur. However, when the hip is flexed it will pull the upper part of the femur medially with the lower part passing laterally, as in abduction.

Functional activity

The functional activity of these muscles must be considered together. Piriformis, the gemelli, obturator externus and internus, and quadratus femoris are always considered in the anatomical position. In this position these muscles will perform an important role in the control of the pelvis, particularly when only one foot is on the ground and even more so in the walking. They are responsible, together with gluteus maximus and the posterior part of gluteus medius, in producing lateral rotation of the lower limb in the forward swing-through phase of gait. In sitting, crawling and turning over when lying down they will, however, have a completely different role, producing abduction of the hip and thereby controlling the movements of the pelvis on the flexed thigh.

Palpation

These muscles are situated deep to the thick gluteus maximus and it is almost impossible to distinguish the contraction of these muscles through the overlying muscle tissue, especially as gluteus maximus is usually contracting at the same time. However, overactivity or strain of these muscles may result in acute tenderness deep to the back of the hip joint; the production of this pain with the relevant movement is then obvious.

It is difficult to research the actions of these lateral rotators primarily because of their depth in the gluteal region, but also because much of their action is concerned with the control of the movements of the hip and pelvis. Thus they may be in a state of contraction even when the opposite movement to their primary action is occurring.

To see these muscles, gluteus maximus must be removed – the muscles resembling the rungs of a ladder: consequently, they are often referred to as the ladder of muscles.