The pectineus muscle is situated deep in the upper thigh and groin region. It is classified as one of the adductor muscles, which move the legs toward the body’s midline, and it also plays an important role as a hip flexor. The pectineus contributes significantly to everyday movements like walking, marching, and maintaining balance. Understanding this muscle helps recognize the source of certain common groin and hip discomforts.
Anatomical Location and Structure
The pectineus is the most anterior muscle in the adductor group of the medial thigh. It acts as a bridge between the pelvis and the thigh bone, providing a mechanical advantage for both adduction and flexion. This muscle originates on the pectineal line of the pubic bone, which is part of the superior pubic ramus in the pelvis. The muscle fibers travel downward and slightly outward toward the thigh.
The muscle inserts on the pectineal line of the femur, just below the lesser trochanter. Its location forms part of the floor of the femoral triangle, an area in the upper thigh that contains important blood vessels and nerves. The pectineus often has a dual nerve supply, receiving input from the femoral nerve and frequently a branch from the obturator nerve. This reflects its functional overlap between the anterior and medial compartments of the thigh.
Primary Functions in Hip Movement
The pectineus muscle moves the thigh at the hip joint through adduction and flexion. Adduction is the action of pulling the leg inward toward the center line of the body. This movement is necessary for activities such as crossing one leg over the other while seated or stabilizing the pelvis when standing on one leg.
The muscle works alongside its neighboring adductor muscles for this inward movement. Because of its anterior position, the pectineus is also a primary hip flexor, helping lift the knee toward the torso. This action is necessary during the swing phase of walking or running, and when lifting the leg to step over an obstacle.
It acts as a synergist to the larger hip flexors like the iliopsoas muscle, particularly in the initial phases of hip flexion. By engaging early, the pectineus helps stabilize the hip and initiate the lifting motion. The muscle also contributes to the rotation of the thigh, which depends on the current position of the hip joint.
When the hip is flexed and abducted, the pectineus assists in external rotation, turning the thigh outward. Conversely, when the hip is extended and adducted, it may contribute to a slight internal rotation. The muscle’s short, strong fibers provide quick, precise control over the femoral head within the hip socket, supporting dynamic, coordinated activities.
Common Injuries and Symptoms
Due to its role in rapid and forceful movements, the pectineus muscle is susceptible to strains, commonly known as groin pulls. These injuries frequently occur in sports that require sudden acceleration, quick changes in direction, or powerful kicking motions, such as in soccer, hockey, or sprinting. The muscle fibers can become damaged or torn when overstretched or subjected to an excessive load.
A strain in the pectineus typically manifests as pain deep within the groin area, sometimes radiating down the inner thigh. The pain can vary from a mild ache that worsens with activity to a sharp, immediate pain felt during the moment of injury. Individuals may experience tenderness upon touching the muscle in the upper inner thigh, and bruising or swelling may also be present.
Difficulty performing actions like walking, running, or bringing the legs together is a common symptom. Crossing the legs can also aggravate the pain, providing a clue that the pectineus may be involved. While most pectineus strains are mild and heal with rest, a severe tear can cause immediate, significant pain and may require temporary support for walking.