ADDUCTOR INJURY

Adductor brevis Adductor brevis is the shortest adductor muscle. Arising from a narrow attachment on the inferior ramus of the pubis, it lies pos- teriorly to adductor longus inserting into the linea aspera (12).

Pectineus Pectineus is a flat muscle in the femoral triangle. The muscle aris- es from the anterior aspect of the pubic ramus and inserts into the linea aspera (12).

Gracilis Gracilis is the weakest, most superficial adductor muscle and is the only muscle in this group to cross the knee joint. Gracilis arises from a thin aponeurosis on the pubis and inserts into the upper area of the medial surface of the tibia (12). Gracilis arises from a flattened tendon where it is strap-like but inserts into the tibia between sar- torius and semimembranosus with a rounded tendon (10).

Anatomical anomalies It is common that anomalies of the musculotendinous junction of adductor longus exist between individuals. Anomalies of the

■ Abdominal muscles BOX 1: ADDITIONAL GROIN MUSCLES FOR CONSIDERATION

■ Hamstring muscles ■ Piriformis, obturator internus, gemelli ■ Sartorius and quadriceps ■ Gluteal muscles ■ Psoas/iliopsoas ■ Tensor fascia lata/iliotibial band

tendon can lead to diagnostic problems. Localising the site of injury can be very difficult and highlights the need for individual management of each patient presenting with an injury. There may occasionally be some fusion of gracilis with adductor longus, brevis or pectineus. Additionally, anomalies of the origin of these four muscles may exist which can make differential diagnosis difficult.

Additional muscles in the groin region There are several other muscle groups to consider in the examina- tion of a patient with groin pain. It can be useful to test and

4. END STANCE PHASE – eccentric control of hip extention 5. SWING PHASE – concentric initiation of swing phase (32) The adductor muscles and the lower abdominal muscles work together to counteract lateral rotation of the pelvis, particularly during the double support phase of walking when the anterior limb is flexed and the posterior limb is extended (20).

This means that an athlete requires good pelvic or core stability to prevent excessive eccentric load on the adductors (21). Single leg stance adductors work with lower abdominals and hip abduc- tors to maintain pelvic stability.

In gait, the adductors work with gluteus medius and minimus to stabilize the pelvic girdle on the femoral head. It is thought that the adductor muscle group may be reflexely inhibited when the sacroiliac joint is unstable. This would result in weakness of the force closure system contributing to compensatory movements of the lumbar spine and lower limbs (30).

The individual adductor muscles also have distinct roles within the phases of the gait cycle: ■ Adductor magnus - during the gait cycle adductor magnus decelerates forward hip flexion and forward thrust of the body with three distinct periods of activity in stance, early swing and middle swing phases (20)

■ Adductor longus - the principle role in the gait cycle is to eccentrically control abduction of the femur on the pelvis with the greatest activity at toe off through recovery phase (22)

■ Gracilis - acts to adduct the hip and assists in hip flexion and internal rotation of the leg (22).

ROLE OF THE ADDUCTOR MUSCLES IN RUNNING As the speed of gait increases, the range of movement of the hip increases and muscles such as the adductor muscles, hamstrings and abductors need to be able to tolerate lengthening to achieve

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increased range of movement. If the adductor muscles are short and tight they will lead to pelvic instability (6). The adductor muscles play an important role after the propulsion phase in run- ning, controlling abduction of the hip (21). At the beginning of the swing phase the adductors are working synergistically with iliopsoas and at the end of swing phase they assist hamstrings to prevent excessive hip flexion (20).

The adductor muscle group is different to many other muscle groups because while helping to maintain pelvic stability these muscles have the ability to provide power for activities involving acceleration and deceleration. The muscles can also interchange- ably contract concentrically and eccentrically, for example in changing direction and kicking while an athlete either speeds up or slows down.

During the single leg phase of running any weakness of the adduc- tor muscles may increase the shearing force on the sacroiliac joint and on the pubic symphysis.

LOSS OF ADDUCTOR MUSCLE POWER The pattern of gait may be dramatically altered in an individual with loss of adductor muscle activity. There will be varying amounts of deficit resulting from obturator nerve damage depend- ing on the degree of injury to the nerve (32).

The abnormal gait pattern in this patient will be characterised by observing them slinging forward their limb and trunk to initiate swing phase. There will be a shortened stance phase on the affect- ed side. They may also throw the pelvis forward on the unaffect- ed side to initiate swing phase (32).

The patient must compensate for the loss of adductor muscle activity in order for lower limb functioning and also to reduce their energy expenditure during gait (32).

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