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Step 1
Read up on Latin roots to know that "piriformis" means "pear-shaped," referring to the shape of this muscle.
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Step 2
Examine the piriformis to see that it laterally rotates the thigh outward and stabilizes the hip.
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Step 3
Observe how the piriformis originates from the two to four costotransverse bars of the anterior sacrum and part of the gluteal spine. A few fibers originate from the superior border of the greater sciatic notch.
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Step 4
Look at the insertion of the piriformis into the anterior part of the medial aspect of the greater trochanter of the femur. The tendon frequently joins with the tendons of the gemellus and obturator internus muscles before the insertion.
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Step 5
Research the nervous system to know that the nerve for the piriformis is the anterior primary rami of the first two sacral nerves. Study the circulatory system to know that the blood supply for the piriformis is the inferior gluteal artery, lateral sacral artery and the superior gluteal artery.
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Step 6
Study the condition known as sciatica that occurs when the piriformis irritates the sciatic nerve. This is more likely to occur in the 15 percent of the population in which the sciatic nerve penetrates the piriformis.
