Muscles adducting the hip joint

Adductor magnus

Adductor longus

Adductor brevis

Gracilis

Pectineus

These muscles are situated on the medial side of the hip joint running down the medial side of the thigh.

Adductor magnus

Adductor magnus is the largest and most posterior of the group, with adductor brevis and adductor longus in front, and semimembranosus and semitendinosus behind. The muscles is really composed of two parts, an adductor part and a hamstring part, forming a large triangular sheet of muscle with a thickened medial margin.

Its upper attachment is from the femoral surface of the ischiopubic ramus running down to the lateral part of the inferior surface of the ischial tuberosity. The part of the muscle which attaches anteriorly to the ischiopubic ramus represents a sheet of muscle which twists before attaching to the femur while the posterior fibres of adductor magnus, from the ischial tuberosity, pass vertically downwards as a thickened cord of muscle fibres.

The ischiopubic fibres fan out and are seen as a large triangular muscular sheet. The most anterior of these fibres pass laterally and slightly backwards to attach to the upper part of the linea aspera continuing upwards as far as the greater trochanter medial to the attachment of gluteus maximus. These upper fibres may be fused with quadratus femoris. Fibres from the posterior part of the ischiopubic ramus attach to the whole length of the linea aspera and medial supracondylar ridge. This attachment to the femur is not continuous as there are small fibrous arches close to the bone which allow vessels and nerves to pass from the adductor to the posterior compartment of the thigh. The posterior ischial fibres pass downwards and attach mainly to the adductor tubercle situated on top of the medial condyle of the femur at the lower end of the medial supracondylar ridge. Some of these fibres continue downwards to fuse with the medial collateral ligament of the knee.

Nerve supply

Because of its two parts, adductor magnus has a dual nerve supply. The adductor part from the ischiopubic ramus is supplied by the posterior division of the obturator nerve (L2, 3), while the hamstring part from the ischial tuberosity is supplied by the tibial division of the sciatic nerve (L4), the skin covering the inner side of the thigh being mainly from L3.

Action

Working as a whole, the muscle is an adductor of the hip joint; although the posterior portion will aid in extension of the hip. Some people believe that this muscle, together with the adductor longus, medially rotates the hip joint, although it was believed in the past that they also acted as lateral rotators. Whether the muscle acts acted a medial or lateral rotator will depend on the position of the thigh, and the line of action of the muscle with respect to the mechanical axis of the femur. All the adductor muscles are important in preventing lateral overbalancing during the support phase of walking.

It is worth noting that the medial collateral ligament of the knee joint appears to be a downwards continuation of the adductor magnus tendon and as such this muscle may very well at some time have crossed the knee joint and therefore have been a flexor of the knee in a similar fashion to gracilis.

Palpation

Adductor magnus is a deep muscle and is therefore difficult to palpate, nevertheless, if the fingers are pushed in just above the medial condyle of the femur, the adductor tubercle can be identified. If the inside of the same foot is now pressed against a stationary obstacle, one can feel the vertical part of the muscle contracting. The muscle can be traced about one-third of the way up the thigh until it becomes hidden by other muscles.

Adductor longus

Adductor longus is a long, slender, triangular muscle situated on the medial aspect of the thigh, overlying the middle part of adductor magnus. Its upper, narrower attachment comes from a small roughened area just below the medial end of the obturator crest on the anterior aspect of the body of the pubis.

Its fibres pass downwards and laterally spreading out as they go to attach to the middle two-quarters of the linea aspera, anterior to adductor magnus below and adductor brevis above and posterior to vastus medialis.

Nerve supply

Adductor longus is supplied by the anterior division of the obturator nerve, root value L2, 3, 4. The skin covering the area of adductor longus is supplied by L3.

Action

Adductor longus is an adductor of the thigh, but as a rotator of the thigh there is some doubt. Adductor longus can also flex the extended thigh, and extend the flexed thigh.

Adductor brevis

Adductor brevis is again a triangular muscle situated on the medial aspect of the thigh.

Its upper attachment is from the lateral part of the front of the body and inferior ramus of the pubis. Its fibres pass downwards, laterally and backwards to attach to the upper half of the linea aspera anterior to adductor magnus. Its upper part is posterior to pectineus and its lower part is posterior to adductor longus.

Nerve supply

Adductor brevis is supplied by the anterior division of the obturator nerve, root value L2, 3, 4. The skin covering the area of adductor brevis is supplied by L2. 

 Action

Adductor brevis is an adductor of the thigh.

Palpation

If the fingers are placed high up on the inside of the thigh and the lower limb is adducted against resistance a mass of muscle can be palpated running down towards the thigh. These are the adductors; however it is difficult to distinguish between the different muscle masses.

The adductors

Gracilis is the most medial muscle of the adductor group. It is an adductor of the thigh as well as flexor of the knee. 

Functional activity

Although it is quite clear that these muscles are adductors of the thigh, they appear to work most strongly when the hip joint is in the neutral position, that is the anatomical position. They certainly work strongly, synergically, when the knee and hip are being flexed and extended when weight-bearing. There is still some confusion over whether these muscles are involved in either medial or lateral rotation of the thigh. They work strongly during walking, as they pull the supporting leg into adduction, thereby moving the line of gravity over the supporting foot. They also contribute to the delicate balancing of the pelvis on the hip joint. The adductors, as a group, are used very strongly when some object is being held between the knees in the sitting position, for example, when sitting on a horse, particularly when the horse is moving.

Gracilis

Gracilis, as its name implies, is a long, thin muscle, situated on the medial side of the thigh. It is the most superifical of the adductor group. Its upper attachment is to the front of the body of the pubis and its inferior ramus, just encroaching on to the ramus of the ischium. The muscle, as it descends between semimembranosus posteriorly and sartorius anteriorly, develops a fusiform-shaped belly at about its middle. It becomes tendinous above the knee and crosses the joint before expanding to attach to a short vertical line on the upper part of the medial surface of the shaft of the tibia. This attachment is above that of semitendinosus and behind and blending with that of sartorius. Bursae separate the tendon of gracilis from those of sartorius and semitendinosus.

Nerve supply

Gracilis is supplied by the anterior division of the obturator nerve, root value L2, 3. The skin covering this area is innervated by roots L2, 3; the upper part by the obturator nerve and the lower part by the femoral nerve.

Action

Although this muscle is situated with the adductor group of muscles, its action of adduction on the thigh is not so important as its action on the knee. It is mainly a flexor of the knee, but with the knee in a semiflexed position it will aid medial rotation of the leg on the thigh.

Functional activity

As a flexor of the knee this muscle will help the hamstrings in simple flexion activities, such as the beginning of the swing phase in walking when the knee needs to be flexed. It will also help when strong flexion is required, as when pulling the body forward on the sliding seat of a rowing boat. In horse riding, gracilis is used in all its actions. When the rider is gripping the horse, gracilis will help the adductor muscles, whilst at the same time helping to control the flexed knee.

Palpation

In the sitting position with the medial aspect of the foot against a solid object, such as the leg of a table, or when the toes are inwardly rotated, the tendon can be felt on the posteriomedial aspect of the knee joint, being the upper of the two obvious tendons. If traced upwards, the belly of the muscle can be palpated and traced to its attachment on the front of the pubic body.

Pectineus

Pectineus is a quadrilateral muscle situated at the upper and medial part of the thigh, deep in the groin. It appears to be made up of two layers, superficial and deep, and these are generally supplied by different nerves.

Its upper attachment is to the superior ramus (pectin) of the pubis, the iliopubic eminence and the pubic tubercle. It also attaches to the fascia which covers it. The fibres pass downwards, backwards and laterally between psoas major and adductor longus to attach to a line which runs from the lesser trochanter of femur to the top of the linea aspera, anterior to the upper part of adductor brevis. This is often called the pectineal line. 

Nerve supply

Pectineus is supplied by the femoral nerve from its L2, 3 nerve roots and occasionally from the obturator or the accessory obturator nerve by its L3 root. The skin covering this area of the groin is supplied from the root of L1.

Action

Pectineus flexed and adducts the hip joint. Some authorities also believe the muscle to be a medial rotator of the hip.

Functional activity

It is easy to see how this muscle acts as a flexor and adductor of the hip by looking at the direction of its fibres, which pass downwards, backwards and laterally. Contraction of the muscle will therefore draw the thigh inwards and forwards. Most authorities dismiss the rotation element as there is certainly disagreement, although some feel that there must be more to the rotation than has yet been deduced.

There is no doubt that the insertion of pectineus is lateral and in front of the mechanical axis of the femur (the line around which rotation would occur in the standing position). Thus the muscle in this case would produce medial rotation. However, when the foot is off the ground, as in the carrying-through phase in walking, the axis would still pass through the hip joint, but now would vary considerably according to the position of the thigh and also that of the pelvis. In fact it would depend very much on the swing of the lower limb.

So far, the functional activity of this muscle has only been considered in the upright, standing or walking position. Much of the time is spent in the sitting position with the hip joint flexed at a right angle. The relationship between the origin and insertion of this muscle is now completely reversed. To make the situation even clearer, the thigh can be raised off the seat until it is at an angle of 45° to the horizontal – as if the legs were going to be crossed. The muscle fibres now pass forwards and upwards, passing well behind the axis of the rotating thigh. The action of the muscle in this position will now be adduction as before, but also extension and lateral rotation; in fact a movement very similar to that of crossing the legs except that the thigh is being pulled down on to the opposite thigh. This movement is comparable with the initial stages of rising from a very low chair, or from the squat position, especially if the movement is being carried out at some speed and under load.

If the argument is taken one stage further, the muscle is obviously a flexor and adductor in the upright position with perhaps medial rotation.

The muscle is an extensor and lateral rotator in the fully flexed position, but still performing adduction. Therefore, as in the case of many muscles in the body, pectineus can perform different actions according to its starting position and the relative position of its origin and insertion. It is not surprising, therefore, that it is supplied by nerves from both the flexor and adductor compartments of the thigh.

Remembering the dual nerve supply, the dual action, the closeness of the muscle to the hip joint and its important relations, it is surprising that pectineus only merits a few lines in most anatomy texts. It must have played a vital role in locomotion with a flexed hip, either in climbing or when all four limbs were on the ground. Has its role diminished that much or are we overlooking the true action and worth of pectineus?