GENERAL INFORMATION
The Piriformis is a small, deep muscle located in the buttock region. It plays a crucial role in hip rotation and stabilisation and its proximity to the sciatic nerve makes it clinically significant.
ORIGIN
The Piriformis originates from the anterior surface of the sacrum, specifically from the second to fourth sacral segments.
INSERTION POINT
It inserts onto the greater trochanter of the femur (the bony prominence on the side of the upper leg bone).
MAJOR ARTERIES
The Piriformis muscle receives blood from branches of the internal iliac artery, including the superior and inferior gluteal arteries.
NEURAL INNERVATION
The Piriformis muscle is primarily innervated by the branches of the sacral plexus, including the ventral rami of the S1 and S2 spinal nerves.
TRIGGER POINT
A common trigger point for the Piriformis muscle is located in the mid-buttock region. It can cause pain that radiates down the back of the leg, mimicking sciatica.
CONCENTRIC FUNCTION
The concentric function of the Piriformis muscle involves contracting its muscle fibres, resulting in the lateral rotation of the hip joint. This action is essential for walking, running and outward leg movements.
ECCENTRIC FUNCTION
The eccentric function of the Piriformis muscle occurs when the muscle fibres lengthen under tension. This function is essential for controlled internal hip rotation during movements such as lowering the leg from an externally rotated position.
ISOMETRIC FUNCTION
The isometric function of the Piriformis muscle involves contracting and generating tension without changing its length. This function helps stabilise the hip joint during weight-bearing activities and maintain proper alignment.
RELATED MUSCLE SCIENTIFIC NAMES
- Gemellus superior: Assists in lateral rotation and stabilisation.
- Gemellus inferior: Aids in external rotation and stability.
- Obturator internus: Contributes to lateral rotation.
- Obturator externus: Involved in external rotation.
- Quadratus femoris: Supports hip rotation and stability.
ANTAGONIST MUSCLES
- Gluteus medius: Involved in hip abduction and internal rotation.
- Gluteus minimus: Assists in hip abduction.
- Tensor fasciae latae: Stabilises and moves the hip.
- Gluteus maximus: Major extensor and lateral rotator of the hip.
COMMON INJURIES
- Piriformis syndrome: Compression or irritation of the sciatic nerve by the Piriformis muscle, resulting in symptoms such as pain, tingling or numbness radiating down the back of the leg.
- Muscle strain or tear: Overstretching or excessive contraction of the Piriformis muscle, leading to muscle fibre damage.
- Myofascial pain syndrome: Development of trigger points in the Piriformis muscle, causing localised pain and referred pain in the buttock and leg.
EXERCISES
- Piriformis stretch: Sit with one leg crossed over the other, gently pulling the knee toward the opposite shoulder.
- Seated hip external rotation: Sit with legs bent and rotate the hip outward.
- Supine figure 4 stretch: Lie on your back, cross one ankle over the opposite knee and pull the leg toward your chest.
- Pigeon pose: A yoga pose that stretches the hip rotators and gluteal muscles.
- Clamshells: Lie on your side with knees bent, then lift the top knee while keeping your feet together.
STRETCHES
- Seated piriformis stretch: Sit with one leg crossed over the other, pulling the knee toward the opposite shoulder.
- Supine figure 4 stretch: Lie on your back, cross one ankle over the opposite knee and pull the leg toward your chest.
- Pigeon pose: Yoga pose that stretches the hip rotators and gluteal muscles.
- Standing cross-leg stretch: Stand with one leg crossed over the other and bend forward.
- Lunge with hip external rotation: Perform a forward lunge and rotate the hip outward.