Massage & Bodywork

July/August 2010

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functional anatomy BY CHRISTY CAEL PIRIFORMIS Piriformis is one of six deep hip external rotators. This group of muscles is located deep to the gluteus maximus and gluteus medius in the posterior pelvis and functions similarly to the rotator cuff in the shoulder. Coordinated activation of these muscles helps stabilize the hip joint and position the femoral head during movements of the lower extremity. The other deep external rotators include superior and inferior gemellus, obturator internus and externus, and the quadratus femoris. Piriformis is the most superior of the deep six external rotators. Its fibers extend laterally between the anterior surface of the sacrum and the greater trochanter of the femur. It functions similarly to the supraspinatus by levering the head of the femur into optimal position while the larger pelvic muscles (gluteals, hip flexors, etc.) perform their actions. Piriformis is unique in that it is strongly PIRIFORMIS Attachments • Origin: sacrum, anterior surface • Insertion: femur, superior border of greater trochanter Actions • Externally rotates the hip • Abducts the hip Innervation • Sacral plexus • L4–S2 associated with the sciatic nerve. This large nerve extends from the sacral plexus through the greater sciatic notch of the pelvis and under or through the piriformis muscle before extending distally into the lower extremity. Tightness in piriformis may compress the sciatic nerve, causing radiating pain, weakness, and altered sensation in the lower extremity. This mimics the symptoms of nerve root compression associated with a protruding intervertebral disc or degenerative changes in the spine. connect with your colleagues on 85

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