The obturator internus is the deep muscle of hip joint which is part of lateral wall of pelvis. It is found in the superior inner side of the obturator membrane.
The obturator internus muscle originates from the inferior margin of the superior pubic ramus and from the pelvic surface of the obturator membrane.
Its tendon exits the pelvis through the lesser sciatic foramen to insert onto the greater trochanter of the femur.
This muscle is innervated by the obturator internus nerve (L5–S2), a branch of sacral plexus.
The primary arterial supply of obturator internus is Superior gluteal artery, the largest branch of internal iliac artery.
- Laterally/ externally rotates the hip
- Abduction of hip
- Hip joint stabilizer(only when torques are applied in the specific directions in which the muscle is active.)
- In the Study done by Solomon et al.(2010), obturator internus has shown its role as a hip stabilizer affecting the impact of posterior approach in total hip replacement (THR).In total hip replacement, posterior approach is the one of the most common procedure which involves detachment of the tendons of piriformis, obturator internus and obturator externus (short external rotators) as they insert into the greater trochanter. However despite the repair of tendons, rate of post surgical hip dislocation is higher as short external rotators also act hip stabilizers. Thus, other approaches are preferable than posterior approach while doing THR.
- Role of obturator internus in pelvic floor rehabilitation: Obturator internus (OI) share fascial attachment with the pelvic floor muscle(PFM), strengthening OI may play an important role in normal function of PFM. In the study done by Lori et al. (2016) had shown the increase in peak pressure and strength of external rotators when strengthening of OI is done together with PFM rehabilitation.
- Obturator strain is associated with the kicking sports due to overuse in young male athletes with initial complain of groin pain.
- Ramirez PT, Frumovitz M, Abu-Rustum NR. Principles of Gynecologic Oncology Surgery E-Book. Elsevier Health Sciences; 2018 Jul 1.(pp.3-49)
- Byrne C, Alkhayat A, O'Neill P, Eustace S, Kavanagh E. Obturator internus muscle strains. Radiology Case Reports. 2017 Mar 1;12(1):130-2.
- Kenhub - Learn Human Anatomy. Obturator internus. Available from: https://www.youtube.com/watch?v=WqufrPruEMc [last assessed: 2019/12/30]
- Hodges PW, McLean L, Hodder J. Insight into the function of the obturator internus muscle in humans: observations with development and validation of an electromyography recording technique. Journal of Electromyography and Kinesiology. 2014 Aug 1;24(4):489-96.
- Solomon LB, Lee YC, Callary SA, Beck M, Howie DW. Anatomy of piriformis, obturator internus and obturator externus: implications for the posterior surgical approach to the hip. The Journal of bone and joint surgery. British volume. 2010 Sep;92(9):1317-24.
- Tuttle LJ, DeLozier ER, Harter KA, Johnson SA, Plotts CN, Swartz JL. The role of the obturator internus muscle in pelvic floor function. Journal of Women's Health Physical Therapy. 2016 Jan 1;40(1):15-9.
- Cook MS, Bou-Malham L, Esparza MC, Alperin M. Age-related alterations in female obturator internus muscle. International urogynecology journal. 2017 May 1;28(5):729-34.
- Khodaee M, Jones D, Spittler J. Obturator internus and obturator externus strain in a high school quarterback. Asian journal of sports medicine. 2015 Sep;6(3).