Gracilis

Introduction

Introduction to Gracilis

The gracilis is a long, strap‑like muscle that lies on the medial aspect of the thigh. It is the only muscle of the medial compartment to cross both the hip and knee joints, extending from the pubis to the proximal tibia as part of the pes anserinus. The gracilis adducts the hip, assists in hip flexion, and flexes and medially rotates the knee. Because of its superficial location, expendability, and consistent anatomy, the gracilis is one of the most commonly used muscles in reconstructive surgery, including free functional muscle transfers and pelvic floor reconstruction. Its tendon is also frequently harvested for ligament reconstruction, notably for the medial patellofemoral ligament (MPFL) and anterior cruciate ligament (ACL) grafts.

Study

1. Origin and Insertion

The gracilis originates by a thin, flat tendon from the anterior surface of the body of the pubis and the inferior pubic ramus, just medial to the origins of the adductor longus and adductor brevis. Its muscle belly descends vertically along the medial thigh. Distally, it forms a long, slender tendon that passes posterior to the medial femoral condyle and inserts onto the upper part of the medial surface of the tibia, as part of the pes anserinus (goose foot). The pes anserinus is the common insertion of the gracilis, sartorius, and semitendinosus tendons.

2. Relations

The gracilis is the most medial muscle of the medial thigh compartment. It is superficial, covered only by the fascia lata and skin, making it easily palpable. Anteriorly, it is related to the adductor longus and adductor magnus. Posteriorly, it lies adjacent to the semimembranosus. Deep to the gracilis are the adductor brevis and adductor magnus. The saphenous nerve and the great saphenous vein run superficial to the muscle in the distal thigh. The tendon of the gracilis forms the upper anterior margin of the popliteal fossa.

3. Nerve Supply

The gracilis is innervated by the anterior division of the obturator nerve (L2, L3, L4). The nerve enters the muscle on its deep surface, near its proximal end. Because of its segmental innervation, the gracilis can be denervated in obturator nerve lesions, but may be spared in injuries that affect only the posterior division.

4. Blood Supply

The gracilis receives its blood supply predominantly from the medial circumflex femoral artery, with additional contributions from the obturator artery and the profunda femoris artery. The main vascular pedicle enters the muscle on its deep surface near the proximal third. The segmental blood supply allows the muscle to be harvested as a free flap or rotated on a proximal or distal pedicle.

5. Actions

The gracilis adducts the thigh at the hip joint and assists in hip flexion. At the knee, it flexes the leg and medially rotates the tibia on the femur when the knee is flexed. It acts as a synergist to the other pes anserinus muscles (sartorius and semitendinosus) in these movements.

6. Clinical Relevance

The gracilis is a workhorse in reconstructive surgery. It can be used as a free functional muscle transfer to restore elbow flexion or finger extension, or as a pedicled flap for perineal, vaginal, and pelvic reconstruction. The gracilis tendon is frequently harvested for ACL reconstruction (often combined with the semitendinosus tendon) or for MPFL reconstruction. A gracilis muscle strain ('groin pull') is common in athletes. Pes anserinus bursitis can involve the gracilis insertion. The gracilis is also a target for botulinum toxin injection in spastic adductor muscles in cerebral palsy. Because it is expendable and its removal causes minimal functional deficit, it is the preferred donor muscle for many plastic and orthopaedic procedures.

Summary

Summary of Gracilis

The gracilis is a long, strap‑like muscle of the medial thigh, originating from the pubis and inserting on the medial tibia as part of the pes anserinus. Innervated by the anterior division of the obturator nerve (L2–L4), it adducts and flexes the hip and flexes and medially rotates the knee. It is the most superficial medial muscle and is clinically invaluable as a tendon graft (ACL, MPFL) and muscle flap for reconstruction.