Adductor Magnus

legsAdductor magnus

The adductor magnus is the largest muscle of the inner thigh and a powerful hip extensor as well as an adductor. It is effectively two muscles sharing a name, with two different nerves.

Adductor magnus is a large triangular sheet filling the inner thigh from the pelvis down to the thigh bone. It is the biggest of the adductors and one of the larger muscles in the body, and it is genuinely two muscles that developed together and kept one name.

The adductor part arises from the pubic and ischial rami and runs outward and downward to attach along most of the length of the back of the thigh bone. The hamstring part arises from the sitting bone — exactly where the hamstrings do — and runs almost straight down to a single point on the inner side of the knee.

The two parts have different nerve supplies, and this is one of the standard examples of dual innervation in the body. The adductor part is supplied by the obturator nerve like the other adductors; the hamstring part is supplied by the tibial division of the sciatic nerve like the hamstrings. Sources differ on the exact segmental levels, and some describe the hamstring part as receiving contributions from more than one level.

They also do different things. The adductor part flexes the hip; the hamstring part extends it. So the same muscle contains fibres pulling the thigh forward and fibres pulling it backward, and its overall effect on hip flexion depends on which part is working and where the hip already is.

The gap at the lower end of the adductor part, where the femoral vessels pass through to the back of the knee, is the adductor hiatus — a piece of anatomy far better known than the muscle.

Training notes

Its hip extension role is what makes it matter for lifting. In a deep squat it contributes to standing up alongside the glutes and hamstrings, and studies of squat mechanics consistently find it among the most heavily loaded muscles at the bottom.

Wide-stance squatting and sumo deadlifting load it most, since those add adduction demand on top of the extension demand.

It also responds to hip extension work generally — Romanian deadlifts and hip thrusts reach the hamstring part in the same way they reach the hamstrings.

Depth is the variable that matters most, as with the glutes. Its contribution rises sharply as the hip flexes further.

Anatomy

Origin
  • Adductor part: inferior ramus of the pubis and the ramus of the ischium
  • Hamstring part: the ischial tuberosity
Insertion
  • Adductor part: the linea aspera and the medial supracondylar line of the femur
  • Hamstring part: the adductor tubercle on the medial condyle of the femur
Actions
  • Adducts the thigh, powerfully — it is the largest adductor
  • Extends the hip, through the hamstring part
  • Flexes the hip, through the adductor part
  • Contributes to rotation of the thigh, with the two parts pulling in opposite directions
Innervation
Adductor part: obturator nerve (L2–L4). Hamstring part: tibial division of the sciatic nerve (L4)

Exercises

Antagonists

Synergists