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Hip Flexors

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Introduction

The hip flexors are the muscles that bring the thigh toward the trunk, or the trunk toward the thigh, at the hip joint, with iliopsoas as the primary flexor.[1] Rectus femoris, sartorius, pectineus and tensor fasciae latae (TFL) assist, and their contribution changes with hip position and load.[2] These muscles work in every step: they swing the leg forward in gait and running, lift the leg to climb stairs and generate the kicking motion, and help bring the trunk forward when rising from a chair or sit-up. Because several of them also cross the knee, pelvis or lumbar spine, hip flexor problems often present as groin, anterior thigh or low back symptoms rather than as isolated hip pain.[3]

Anatomy

Six muscles contribute to hip flexion; psoas minor is listed because it runs with them buthas no hip action

Muscle Proximal attachment Distal attachment Innervation Main actions at the hip
Psoas major T12–L5 vertebral bodies and discs;L1–L5 transverse processes[4] Lesser trochanter, via the iliopsoas tendon[5] Anterior rami L1–L3[6] Flexion; stabilises the lumbar spine[7]
Iliacus Iliac fossa[8] Lesser trochanter and femoral shaft just below it[9] Femoral nerve (L2–L4)[10] Flexion[11]
Psoas minor (inconstant) T12–L1 vertebral bodies[12] Pecten pubisand iliopubiceminence[13] L1 anterior ramus[14] Weak lumbar flexion; no hip action[15]
Rectus femoris Anterior inferior iliac spine; superior acetabular rim[16] Patella, then tibial tuberosity[17] Femoral nerve(L2–L4)[18] Hip flexion; knee extension[19]
Sartorius Anterior superioriliac spine[20] Proximal medialtibia (pesanserinus)[21] Femoral nerve(L2–L3)[22] Hip flexion,abduction,external rotation; knee flexion[23]
Pectineus Superior pubic ramus (pectineal line)[24] Pectineal line of femur[24] Femoral nerve; often obturator[24] Hip flexion,adduction[24]
Tensor fasciae latae Anterior superior iliac spine;anterior iliac crest[25] Gerdy'stubercle, via the iliotibial tract[25] Superior gluteal nerve(L4–L5)[25] Hip flexion,abduction,internal rotation[25]
Hip muscles anterior aspect.
Hip muscles anterior aspect.

Anatomical variants matter clinically:

Psoas minor is absent in many people. Cadaveric series report it in roughly one third to just over half of specimens, so the commonly quoted figure of about 60% sits at the top of the range.[26][27]

Iliopsoas tendon: In cadaveric studies, more than half of specimens have two or three separate tendons at the lesser trochanter, not a single conjoint tendon.[27] [28] This is relevant to internal snapping hip and to the extent of surgical release.[27]

Iliopsoas bursa: lies between the tendon and the anterior hip capsule and pubis, and can communicate with the hip joint in some individuals.[29]

Function

Hip flexion force depends on which joints each muscle crosses.

Biarticular muscles

Rectus femoris and sartorius cross both hip and knee, so their hip action is influenced by knee position. Rectus femoris is loaded most when hip flexion and knee extension combine, as in kicking.[16][19][20]

Pelvis and lumbar spine

Psoas major attaches to the lumbar vertebrae, and iliopsoas,rectus femoris and TFL act on the pelvis. Their balance with the abdominals and hip extensors influences pelvic tilt and lumbar posture.[7][19][25]

Position dependence

The adductors and TFL change their contribution to flexion with the starting hip angle, which is why testing position matters when assessing hip flexor strength or length.[30]

Prime Movers

The prime movers (agonist) for hip flexion are the:

  1. Psoas major muscle, a long, tapering (fusiform) muscle that originates at either side of the spine and inserts at the lesser trochanter of the femur. The psoas muscle contracts when the hip is flexed. The psoas minor is a normal anatomic variant present in approximately 60% of people.
  2. Iliacus muscle. The iliacus muscle is a triangular sheet that connects the ilium bone to the lesser trochanter.
iliopsoas Bursa.
iliopsoas Bursa.

The iliacus and psoas muscles are often grouped together as the iliopsoas musculotendinous unit secondary to overlapping function and anatomic proximity. The iliopsoas has an associated bursa that is the largest bursa in the body and lies between the iliopsoas and the hip capsule/pubis.

Synergists

Kicking a soccer ball.
Kicking a soccer ball.

The rectus femoris is one of the quadriceps and a hip flexor muscle and has two functions: flex at the hip; extend the knee.[32]. Rectus Femoris is engaged intensely when both functions are at play, such as when kicking a soccer ball or swinging a straight leg forward.

The sartorius, the longest muscle in the body, crosses the hip and the knee joints. It originates at the anterior superior iliac spine and inserts superficially on the pes anserinus as a broad fascial insertion. It functions to flex the hip, and secondarily to adduct the thigh and externally rotate the leg. Like with Rectus Femoris, great effort from Sartorius is required during a soccer kick, particularly when kicking across the body.[33]

The pectineus acts as a hip flexor and secondary adductor from its origin on the superior pubic ramus and insertion on the pectineal line of the femur[32].

Physiotherapy Relevance

Postural Issues

Desk workers
Desk workers

Sitting too long or all day shortens and tightens these the hip flexor muscles. This condition is a common problem with with people who sit for many hours daily eg anyone who sits at a desk for hours each day; bus drivers. Shortened muscles are unable to generate as much power as lengthened muscles, which can lead to functional problems.eg causes anterior pelvic tilt and a lumbar hyperlordosis[34].

Hip flexor stretch
Hip flexor stretch

See also Principles of Biomechanics in Hip Flexion Contracture

Another hip flexor issue related is Lower Crossed Syndrome. In LCS there is overactivity and tightness of hip flexors and lumbar extensors. Along with this there is underactivity and weakness of the deep abdominal muscles on the ventral side and of the gluteus maximus and medius on the dorsal side.

Injuries

soccer kick
Soccer kick

Athletic injuries to the hip flexors and iliopsoas have been described in populations across all levels of competitive sports. Estimates of hip flexor pathology ranges from 5% of injuries all the way to 28% of injuries among high-risk sport-specific groups. Although most of these injuries are successfully treated with conservative management, and high rates of return to play are observed, significant rehabilitation time can be involved.[31]

Poor posture, general overuse, and sometimes arthritis can also cause pain in the hip flexors.[34]

  • Strains, tears, tendinosis, and bursitis of the iliopsoas muscle can all present similarly.
  • Overuse or eccentric hip flexion against resistance is often the cause.
  • Bursitis or tendinosis is caused by overuse of the iliopsoas tendon resulting in friction as the tendon glides over the iliopectineal eminence.
Dancers are prone to hip pain at some point.
Dancers are prone to hip pain at some point.

Symptoms of an iliopsoas strain or tear are typically:

  • groin and/or proximal medial thigh pain, which are exacerbated by actively flexing the hip against resistance
  • pain with passive extension of the hip by stretching the iliopsoas tendon
  • tenderness over the femoral triangle
  • swelling may also be palpated in the femoral triangle region.

Image 7: A potential hip injury move

Image 8: There is hardly a dancer who has never had some hip pain at some point.

See Also

References

  1. ↑ Juan J, Leff G, Kevorken K, Jeanfavre M. Hip flexor muscle activation during common rehabilitation and strength exercises. Journal of Clinical Medicine. 2024 Nov 4;13(21):6617.
  2. ↑ Lewis CL, Sahrmann SA, Moran DW. Effect of position and alteration in synergist muscle force contribution on hip forces when performing hip strengthening exercises. Clinical Biomechanics. 2009 Jan 1;24(1):35-42.
  3. ↑ Prather H, van Dillen L. Links between the hip and the lumbar spine (hip spine syndrome) as they relate to clinical decision making for patients with lumbopelvic pain. PM&R. 2019 Aug;11:S64-72.
  4. ↑ Kepler CK, Bogner EA, Herzog RJ, Huang RC. Anatomy of the psoas muscle and lumbar plexus with respect to the surgical approach for lateral transpsoas interbody fusion. European Spine Journal. 2011 Apr;20(4):550-6.
  5. ↑ Manske RC, Voight M, Wolfe C, Page P, Bardowski B. The use of diagnostic musculoskeletal ultrasound for the evaluation of the Iliopsoas in the anterior hip: A guide for rehabilitation providers. International Journal of Sports Physical Therapy. 2024 Dec 2;19(12):1642.
  6. ↑ Siccardi MA, Tariq MA, Valle C. Anatomy, bony pelvis and lower limb: psoas major. InStatPearls [Internet] 2023 Aug 8. StatPearls Publishing.
  7. ↑ 7.0 7.1 Penning L. Psoas muscle and lumbar spine stability: a concept uniting existing controversies: critical review and hypothesis. European Spine Journal. 2000 Dec;9(6):577-85.
  8. ↑ Stella SM, Saponara A, Gualtierotti R, Vita F, Miccoli M, Becciolini M, Galletti S, Cotellessa F, Trompetto C. Thickening of the Intramuscular Fascia of the Iliacus Muscle as Evidence of Myofascial Pathology: A New Hip Pain Syndrome. Pain and Therapy. 2025 Dec;14(6):1935-47.
  9. ↑ Gómez-Hoyos J, Schröder R, Palmer IJ, Reddy M, Khoury A, Martin HD. Iliopsoas tendon insertion footprint with surgical implications in lesser trochanterplasty for treating ischiofemoral impingement: an anatomic study. Journal of Hip Preservation Surgery. 2015 Dec 1;2(4):385-91.
  10. ↑ Seijo-Martınez M, del Rı́o MC, Fontoira E, Fontoira M. Acute femoral neuropathy secondary to an iliacus muscle hematoma. Journal of the neurological sciences. 2003 May 15;209(1-2):119-22.
  11. ↑ Kumazaki T, Takahashi T, Nakano T, Sakai T. Action and contribution of the iliopsoas and rectus femoris as hip flexor agonists examined with anatomical analysis. Juntendo Medical Journal. 2022;68(4):352-62.
  12. ↑ Guerra DR, Reis FP, Bastos AD, Brito CJ, Silva RJ, Aragão JA. Anatomical study on the psoas minor muscle in human fetuses. International Journal of Morphology. 2012.
  13. ↑ Raja B, Kulkarni MM, Vaishnani H. Morphology and Morphometric Analysis of the Psoas Minor Muscle in Adult Human Cadavers at a Tertiary-Care Institution in Western India. Cureus. 2026 Jun 24;18(6).
  14. ↑ Agichani S, Sontakke Y, Joshi SS, Joshi SD. Morphology of psoas minor muscle-reviewed. J Evolution Med Dent Sci. 2013 Aug 5;2:5867-9.
  15. ↑ Singh D, AgArwAl S. Morphological Study of Psoas Minor Muscles with Embryological Basis and Clinical Insights. Journal of Clinical & Diagnostic Research. 2021 Apr 1;15(4).
  16. ↑ 16.0 16.1 Carton P, Filan D. Anterior inferior iliac spine (AIIS) and subspine hip impingement. Muscles, Ligaments and Tendons Journal. 2016 Dec 21;6(3):324.
  17. ↑ Flores DV, Mejía Gómez C, Pathria MN. Layered approach to the anterior knee: normal anatomy and disorders associated with anterior knee pain. Radiographics. 2018 Nov;38(7):2069-101.
  18. ↑ Patton RS, Runner RP, Lazarus D, Bradbury TL. Femoral neuropathy following direct anterior total hip arthroplasty: an anatomic review and case series. Journal of Surgical Case Reports. 2018 Sep;2018(9):rjy171.
  19. ↑ 19.0 19.1 19.2 Aguilera‐Bohorquez B, Gil E, Fonseca J, Fernandez M, Sánchez M. Tenosuspension of the reflected head of the rectus femoris in hip arthroscopy: Description of a portal and a surgical maneuver. Arthroscopy techniques. 2017 Aug;6(4):e1015-9.
  20. ↑ 20.0 20.1 Yi KH, Lee JH, Lee DK, Hu HW, Seo KK, Kim HJ. Anatomical locations of the motor endplates of sartorius muscle for botulinum toxin injections in treatment of muscle spasticity. Surgical and Radiologic Anatomy. 2021 Dec;43(12):2025-30.
  21. ↑ Ashaolu JO, Osinuga TS, Ukwenya VO, Makinde EO, Adekanmbi AJ. Pes anserinus structural framework and constituting tendons are grossly aberrant in Nigerian population. Anatomy research international. 2015;2015(1):483186.
  22. ↑ Walters BB, Varacallo M. Anatomy, bony pelvis and lower limb, thigh sartorius muscle.
  23. ↑ Dziedzic D, Bogacka U, Ciszek B. Anatomy of sartorius muscle. Folia morphologica. 2014;73(3):359-62.
  24. ↑ 24.0 24.1 24.2 24.3 Dede BT, Oğuz M, Alyanak B, Bağcıer F. Orphan muscle of groin pain: ultrasound imaging of the pectineus muscle. Journal of Ultrasonography. 2024 Dec 31;24(99):1-2.
  25. ↑ 25.0 25.1 25.2 25.3 25.4 Gottschalk FR, Kourosh SO, Leveau B. The functional anatomy of tensor fasciae latae and gluteus medius and minimus. Journal of anatomy. 1989 Oct;166:179.
  26. ↑ Kokati DB, Jayaayaprakash BR, Smitha M, Eligar RA. A cadaveric study on incidence and morphology of psoas minor muscle in South Indian population. Int J Anat Radiol Surg. 2022;11:29-32.
  27. ↑ 27.0 27.1 27.2 Lin B, Bartlett J, Lloyd TD, Challoumas D, Brassett C, Khanduja V. Multiple iliopsoas tendons: a cadaveric study and treatment implications for internal snapping hip syndrome. Archives of Orthopaedic and Trauma Surgery. 2022 Jun;142(6):1147-54.
  28. ↑ Philippon MJ, Devitt BM, Campbell KJ, Michalski MP, Espinoza C, Wijdicks CA, LaPrade RF. Anatomic variance of the iliopsoas tendon. The American journal of sports medicine. 2014 Apr;42(4):807-11.
  29. ↑ Corvino A, Venetucci P, Caruso M, Tarulli FR, Carpiniello M, Pane F, Sabatino V, Franzese R, Catalano O, Corvino F, Catelli A. Iliopsoas bursitis: the role of diagnostic imaging in detection, differential diagnosis and treatment. Radiology Case Reports. 2020 Nov 1;15(11):2149-52.
  30. ↑ Kato T, Taniguchi K, Kikukawa D, Kodesho T, Katayose M. Effect of hip flexion angle on stiffness of the adductor longus muscle during isometric hip flexion. Journal of Electromyography and Kinesiology. 2021 Feb 1;56:102493.
  31. ↑ 31.0 31.1 Musculoskeletal Key Hip Flexors Available:https://musculoskeletalkey.com/hip-flexor-injuries-in-the-athlete/ (accessed 14.1.2022)
  32. ↑ 32.0 32.1 Biology dictionory Hip Muscles Available: https://biologydictionary.net/hip-muscles/(accessed 14.1.2022)
  33. ↑ Back muscle solutions Hip flexor anatomy Available: https://backmusclesolutions.com/blogs/the-ql-blawg/hip-flexor-muscles-anatomy (accessed 14.1.2022)
  34. ↑ 34.0 34.1 POSMC What is a hip flexor Available: https://www.posmc.com/what-is-a-hip-flexor/(accessed 14.1.2022)
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