Piriformis

Anatomy

Origin	Anterior surface of the sacrum (between the S2 and S4), Gluteal surface of ilium (near posterior inferior iliac spine), (Sacrotuberous ligament)
Insertion	(Apex of) Greater trochanter of the femur
Action	Hip joint: Thigh external rotation, Thigh abduction (from flexed hip); Stabilizes head of femur in acetabulum
Innervation	Nerve to piriformis (S1-S2)
Blood supply	Superior gluteal artery, inferior gluteal artery, gemellar branches of the internal pudendal

Souurce Link

Source Link

Pace Abduction Test

Testing for: the strength of the piriformis muscle

Procedure:

Patient is seated, with their hips flexed 90 ° and their knees together
Therapist places both hands on the lateral side of the knees , holding them together
Patient attempts to move their knees apart while the therapist resists

Positive Sign: piriformis weakness if the patient cannot move their knees apart. Pain is present in the area of the piriformis indicates piriformis trigger points

Piriformis Length Test

Assessing For: the length of the piriformis muscle

Procedure:

Patient is prone with their knees close together
Patient flexes both their knees to 90°
Slowly separate the lower legs away from the midline, while keeping the knees together (the internal rotation of the femur stretches both piriformis muscles)
The normal internal rotation would be (45°-50°) from the midline

Positive Sign: short piriformis muscle is indicated if the internal rotation is less than 45°