The obturator internus is the name of a fan-shaped muscle which commences near the obturator foramen on the pubis’ medial surface, features varied vital fascial connections, continues posterior-laterally, and connects to the femur’s greater trochanter’s inner surface. Along with 5 other muscles, the obturator internus is classified as the ‘deep six’ muscles that help externally rotate the hip and also contribute towards abduction, extension, stabilization, and flexion of the hip.
The obturator internus internal muscle starts on the obturator membrane’s medial surface, the ischium next to the membrane, and the pubis’ edge. It passes out via the lesser sciatic foramen, thereby exiting the pelvic cavity. The muscle is partially located inside the lesser pelvis and partially towards hip-joint’s posterior area. It is supplied by a nerve which commences in the 1st and 2nd sacral nerves and the fifth lumbar nerve.
Obturator internus: Structure and Function
- The obturator internus originates from the inner surface of the pelvic front-lateral wall where it encloses the obturator foramen’s greater part, connects to the ischium and lower pubic ramus, and laterally to the hip bone’s inner surface, under and at the back of the pelvic rim, reaching from the greater sciatic foramen’s upper part, above and at the back of the obturator foramen, under and anteriorly.
- The obturator internus also arises from the obturator membrane’s pelvic surface except from the back area, from the arch of the tendon which completes the passage canal of the obturator nerves and vessels, and slightly from the obturator fascia that encloses the muscle. The fibers rapidly converge near the lesser sciatic foramen, and finish in 4 to 5 tendon-like bands that occur on the muscle’s deep surface. The bands get reflected at right angles above the ischium’s grooved surface between its tuberosity and spine. The tendon inserts into the proximal femur’s greater trochanter.
- Bands/bursa: The bony surface is enclosed by even cartilage, which is removed by a bursa from tendon, and shows 1 or more grooves relating with the furrows occurring between the tendon-like bands. These bands exit the pelvic cavity via the lesser sciatic foramen and come together to form one smooth tendon that runs horizontally across the hip-joint’s capsule, and after getting inferior and superior gemellus muscle attachments, inserts into the fore-section of greater trochanter’s medial surface, over the trochanteric fossa.
- Obturator internus muscle function: The obturator internus laterally rotates the thigh and thus helps it move away from the body’s center. In flexed position of the thigh, the muscle helps other muscles in outward motion of the thigh, away from the body’s midline. It also assists in stabilizing the hip joint. The obturator internus muscle is instrumental in femur abduction with hip flexion and lateral femur rotation with hip extension. It also helps keeps the femoral head steady in the acetabulum.
Obturator internus: Pain and other problems
- The pudendal nerve and the internal pudendal vessels cross the internal obturator muscle and are covered by Alcock’s canal, a special canal created by the obturator fascia. The pudendal nerve occurs from branches of S3, S2, and S4. It innervates the motor function of the perineum muscles and is the genitalia’s main sensory innervation source. The nerve may get trapped at times by the obturator internus’ fascia thereby causing pain and other unusual pelvic symptoms.
- The pudendal nerve consists of three smaller nerve braches, i.e., the perineal nerve which supplies the perineum, urethra, vagina, labia, and male scrotum; the inferior rectal nerve which supplies the skin, rectum, and anal sphincter; and the dorsal nerve which supplies the penis or clitoris.
- Sensory symptoms associated with the pudendal nerve and obturator internus may thus occur as burning, cold, itching, and tingling sensations or sharp and radiating pain in the groin, legs, abdomen, or buttocks.
- It may be noted that the pudendal nerve has autonomic as well as somatic fibers. It means that the patient may experience the above listed problems as well as other symptoms like increased blood pressure, rapid heart rate, malaise, and/or constipation.
Treatment of obturator internus pain and other problems
Patients need to contact a doctor and/or a manual therapist to diagnose the cause of obturator internus pain and according treat it. The therapist will help carry out myofascial stretching of the internal obturator muscle thereby also affecting its several fascial attachments.
Reinforcement of the obturator internus via exercise is also recommended. Reinforcement in an open chain is ideal for performance in sports, while closed chain reinforcement is great for pumping and positively affecting the glands and organs present in the pelvis.
- An excessively tight internal obturator muscle can pull the pelvis a little too forward, thereby causing lower back strain and eventually increasing the risk to arthritic changes in the hips and pelvis. The muscle needs to be strong without increased tenseness or tightness.
- If there is any discomfort or pain in the groin or lower back, then obturator internus strengthening exercises need to be stopped immediately.
- Stretch an excessive tight internal obturator muscle before continuing with strengthening exercises. For this, sit on a chair and keep the feet apart in the width of the hips. Lift the left ankle and keep it over the right ankle, bend forwards and the left hip will be stretched. Repeat 5 times, switch the ankles placements, and then stretch the right hip 5 times.
- Sit on a chair with the feet on the ground, the legs hips-width apart, and the knees bent at right angles. Place the hands on the outer side of each knee. Now push the knees inwards towards one another using the hands, while simultaneously using the legs to exert pressure and prevent the knees from coming together. Hold for about 5 seconds and repeat about 10 times.
- Stand straight with the feet hip-width apart. Prevent hip motion by placing the hands on the hips. Keep the feet firmly planted on the ground and slide the right foot outside towards the right. Repeat 5 times, switch to other foot, and slide the left foot towards the left.
Keep the focus on the exercises when performing them for maximum output. Combine them with tightening techniques such as mild squats to strengthen the muscle.