What is Piriformis Test?
The piriformis test is used to assess the effect of the piriformis muscle on the sciatic nerve. It’s primary function is to detect the tightness of the piriformis muscle. The piriformis muscle is a flat and small muscle located deep in the buttock (just behind the Gluteus maximus).
The sciatic nerve originates at the bottom of the spine and runs across the back of each leg to the foot. The nerve supplies most of the regions of the thigh, legs and foot. To study the piriformis muscle’s impact on the sciatic nerve, you will have the go through the anatomy of the piriformis muscle and the sciatic nerve.
Anatomy of the Piriformis muscle
Piriformis Muscle origin
The piriformis muscle originates from
- The anterior surface (front surface) of the sacrum between the S2 and S4.
- Sacrotuberous ligament
- Superior margin of this greater sciatic notch
Piriformis Muscle Insertion
It then inserts on the apex of the greater trochanter of the femur.
- Adduction of the hip
- External rotation of the femur/thigh at the hip joint.
- Even it also stabilizes the hip joint.
Anatomy of the Sciatic Nerve
However, the sciatic nerve is the longest as well as the largest nerve in the human body. An opening in the pelvis known as the greater sciatic foramen, the sciatic nerve travels through it, and after that, multiple anatomical variations is seen in sciatic nerve anatomy. These anatomical variations vary from person to person.
- In some persons, the sciatic nerve passes above the piriformis muscle.
- While in some peoples, the nerve passes below the piriformis muscle.
- In some cases, a divided sciatic nerve passes above and below the piriformis muscle.
- Sometimes the nerve divides into two parts above the piriformis muscle, one part passes through the piriformis muscle, and the other part passes below the piriformis muscle. This version is the most common.
- Sometimes in individuals, the nerve remains undivided, and it passes alone through the piriformis muscle.
This varies from person to person. That’s why the problem in the piriformis muscle can lead to irritation in the sciatic nerve. The cases mentioned above where the sciatic nerve divides into two parts above the piriformis muscle will instantly unite again and course down as one nerve.
Therefore, the piriformis test is used to screen and detect the tightness of the piriformis muscle or other distress of the sciatic nerve.
Procedure for Performing Piriformis Test
- The patient should lie in a sideline position at the edge of the table.
- The examiner then brings the patient’s upper leg into 60 degrees of hip flexion.
- Now the knee will be in a flexed position, and the tested leg will be completely extended.
- The examiner then fixates the pelvis with one hand. And finally with the other hand, the examiner applies downward pressure at the knee.
Positive Piriformis Test
When the patient complains of pain in the buttock area or radiating pain down, the tested leg’s backside indicates a positive piriformis test. And the positive piriformis test indicates piriformis syndrome.