The piriformis muscle is one of the six deep rotators of the hip and lies deep to the gluteal muscles. Even though it is small, it plays a vital role in hip mechanics and conditions such as piriformis syndrome, where the piriformis muscle compresses the sciatic nerve as it exits the greater sciatic foramen. There are numerous causes of piriformis syndrome, but most of them have some degree of piriformis tightness involved.

The Sciatic Nerve and Gait

The sciatic nerve has two primary divisions and in some cases one or both divisions may pass directly through the piriformis muscle. In this case, it’s easy to understand how hypertonicity in the piriforms muscle could squeeze the sciatic nerve and cause radiating neurological symptoms. In other cases, hypertonicity in the piriformis may compress the sciatic nerve against an adjacent structure, such as the sacrospinous ligament. Myofascial trigger points are also likely to be present when the hypertonic piriformis is causing some of these complications.

Hypertonicity in the piriformis and other hip rotators is often observed during gait patterns with what is commonly referred to as turnout of the foot, wherein the distal end of the foot points laterally. Turnout is easy to observe if the person is walking on a beach or in the snow where footprints are left. A slight degree of turnout is normal and should not be considered pathological. However, excessive turnout is commonly indicative of shortness or tightness in the piriformis muscle.

Why Stretching Helps

Muscular hypertonicity is commonly treated by some variation of compression, deep longitudinal stripping, stretching, or a combination of those. However, the piriformis lies deep to the large gluteus maximus, so it is more challenging to deliver deep specific treatment to that muscle. In addition, direct pressure, whether by static compression or deep stripping methods, could further irritate the existing nerve compression. For that reason, stretching is advocated for addressing the tight piriformis. Stretching is especially helpful in a condition like piriformis syndrome where direct compression or deep stripping techniques may run the risk of increasing nerve compression symptoms.

There is a unique feature of the piriformis muscle that may cause certain common piriformis stretching positions to seem counterintuitive. The piriformis is attached to the anterior face of the sacrum proximally and to the upper regions of the greater trochanter of the femur distally (Figure 1). Its primary action is lateral rotation of the femur, although it contributes to other actions as well. For example, when the thigh is flexed to 90 degrees, the piriformis is a more prominent hip abductor.

The piriformis muscle is similar to several other muscles in the body in that it may change its primary action depending on the relative position of the joint(s) it crosses. Let’s take a look at how this works in the piriformis.

Piriformis Tendon

Notice the distal attachment of the piriformis tendon across the top side of the greater trochanter of the femur in Figure 1. Also, notice that the greater trochanter of the femur is “pointing” upwards. Viewing the greater trochanter from above the piriformis attachment is slightly in front of (anterior) to the axis of rotation for the femur. Certain tendon fibers also wrap around the trochanter from the back side. Therefore, if the hip is in a neutral position when the piriformis contracts, it pulls along the back side of the trochanter and forces the femur to rotate laterally as the front side of the femur is pulled laterally.

However, the main action of the piriformis changes significantly when the hip is in about 60 degrees or more of flexion. In this position, the upper margin of the greater trochanter ‘points’ in a downward direction, changing the piriformis’ action. With the hip flexed, the piriformis pulls the femur in medial rotation instead of lateral. Once you are past 60 degrees of hip flexion, the piriformis becomes a medial rotator and a prominent hip abductor.

The position shown in Figure 2 is commonly used to stretch the piriformis (image shows a left side piriformis stretch). If you perform this stretch on yourself, you can probably feel the deep sensation of stretching as you pull the hip closer to your chest. However, note that the left hip is laterally rotated in this position. If the piriformis kept its same primary action that it has when the hip is in a neutral position (lateral rotation), this position wouldn’t be stretching the muscle, but shortening it instead.

Understanding the biomechanical forces at play in various stretching positions is very helpful for knowing how to target a specific muscle for stretching. Understanding the complexities of hip joint mechanics will help you develop optimum treatment and home care suggestions that will be most effective for your client.

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