Anatomy and supply
The adductors of the hip are part of the inner hip musculature and range from the lower pelvic bone to the femur and knee region. Thereby it lies in between the extensor and flexor group of the thigh muscles. The hip adductors shape the surface anatomy of the medial thigh. The innervation is mainly supplied by the obturator nerve which arises from the lumbar plexus and reaches the adductors through the obturator canal; two muscles have a double innervation. The hip adductors are as follows:
- Pectineus muscle: runs from the superior pubic ramus to the pectineal line and linea aspera of the femur. It is additionally innervated by the femoral nerve.
- Adductor magnus muscle: is one of the biggest muscles of the human body. It originates at the inferior pubic ramus, the ischial ramus and the ischial tuberosity and inserts both at the linea aspera (“fleshy insertion”) and the medial epicondyle (“tendinous insertion”). The superficial part of the adductor magnus is supplied by the tibial nerve.
- Adductor longus muscle: has its origin at the superior pubic ramus and the pubic symphysis and insertion at the linea aspera. Distally it forms an aponeurosis extending to the vastus medialis muscle (vastoadductorial membrane).
- Adductor brevis muscle: originates at the inferior pubic ramus and inserts at the linea aspera.
- Adductor minimus muscle: describes the inconstant cranial separation of the adductor magnus which is found in many people. It extends from the inferior pubic ramus to the linea aspera.
- Gracilis muscle: runs from the inferior border of the pubic symphysis to the medial surface of the tibia, where it inserts as the superficial pes anserinus. Its tendon is easy to palpate in the inguinal region – together with the tendon of the adductor longus muscle.
Both the femoral artery and vein as well as the saphenous nerve proceed within a groove between the adductor magnus, adductor longus and vastus medialis muscles. This so-called adductor canal (Hunter’s canal) is ventrally covered by the vastoadductorial membrane. Distally it ends between the “fleshy” and “tendinous” insertion of the adductor magnus and leads to the popliteal fossa.
As the name suggests the main function of the hip adductors is the adduction of the hip joint. Furthermore it supports the outward rotation (pectineus, adductor minimus, brevis and magnus), inward rotation (tendinous insertion of the adductor magnus), flexion (all) and extension (tendinous insertion of the adductor magnus). Being the only two joint adductor the gracilis muscle moves the knee joint as well where its contraction causes a flexion and inward rotation. The hip adductors are particularly used when crossing one’s legs. Overall they play an important role in balancing the pelvis during standing and walking.
The adductor muscle tear (groin strain) ranks among the most common sport injuries (e.g. playing soccer, doing the splits, slipping on ice etc.) and affects favorably the origin tendon at the pubic region. It is caused by a disproportional strain of the muscles, often in combination with a poor warm-up and a lack of stretching. Hereby even ruptures and hemorrhages may occur. Symptoms include pain extending to the inguinal and knee region when stretching and straining the muscles. A malposition of the sacroiliac joint can restrict the function of the hip adductors in the long run as well and should be addressed clinically.
The above mentioned orthopedic pathologies are to be distinguished from the neurogenic adductor spasm. This is a common symptom in spastic diplegia (Little’s disease). Due to the spasticity in the hip adductors the affected children walk – if at all – with adducted, flexed and inward rotated legs (scissor gait).