GENERAL INFORMATION
The Obturator Internus is a small, deep muscle in the hip region. It also plays a crucial role in hip stability, external rotation and hip joint abduction.
ORIGIN
The Obturator Internus originates from the internal surface of the obturator membrane, the obturator foramen and the surrounding bony margin.
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 Obturator Internus muscle receives blood supply from branches of the internal iliac artery. It also includes the internal pudendal and obturator arteries.
NEURAL INNERVATION
The nerve innervates the Obturator Internus muscle to the obturator internus, which arises from the sacral plexus (ventral rami of S1-S2 spinal nerves).
TRIGGER POINT
Trigger points in the Obturator Internus muscle are relatively rare but may cause referred pain to the hip or buttock region.
CONCENTRIC FUNCTION
The concentric function of the Obturator Internus muscle involves the contraction of its muscle fibres, resulting in the external rotation of the hip joint. This action is essential for walking, running and outward leg rotations.
ECCENTRIC FUNCTION
The eccentric function of the Obturator Internus muscle occurs when the muscle fibres lengthen under tension. It aids in controlling the internal rotation of the hip during movements such as lowering the leg from an externally rotated position.
ISOMETRIC FUNCTION
The isometric function of the Obturator Internus 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.
- Gemellus inferior: Aids in external rotation and stability.
- Piriformis: Participates in hip stabilisation.
- Quadratus femoris: Supports hip rotation and stability.
- Obturator externus: Contributes to external rotation.
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
- Strains or tears: Overstretching or excessive contraction of the Obturator Internus muscle, leading to muscle fibre damage.
- Myofascial pain syndrome: Development of trigger points in the Obturator Internus muscle, causing localised pain and referred pain in the hip and also in the buttock region.
EXERCISES
- Clamshells: Lie on your side with knees bent, then lift the top knee while keeping feet together to target the Obturator Internus.
- Side-lying leg lifts: Lie on your side and lift the top leg to strengthen the lateral rotators.
- External rotation with resistance band: Use a resistance band to perform hip external rotations.
- Bridge with external rotation: Perform a bridge exercise and add external rotation to engage the Obturator Internus.
- Standing hip external rotation with cable machine: Use a cable machine to perform standing hip external rotations.
STRETCHES
- Seated hip external rotation stretch: Sit with your legs bent and gently press the knees inward.
- Supine figure 4 stretch: Lie on your back, cross one ankle over the opposite knee and pull the leg towards your chest.
- Pigeon pose: Perform a yoga pose that stretches the hip rotators and gluteal muscles.
- Lunge with hip external rotation: Perform a forward lunge and rotate the hip outward to stretch the Obturator Internus.
- Standing cross-leg stretch: Stand with one leg crossed over the other and bend forward to stretch the lateral rotators.