Femur

Function

The body’s longest bone

The femur, also called the thigh bone, is the single bone in the thigh¹. It is the longest and strongest bone in the body^1,2. It makes up about a quarter of a person’s height^1,2.

The hips are wider than the knees, so the femur runs at a slant down the thigh¹. This slant is the Q-angle (the angle between the line of the thigh and the line of the shin, seen from the front)¹. It is normally 10 to 15 degrees, and it is typically larger in females¹.

The top end: head, neck and trochanters

The rounded head at the top of the femur fits into the acetabulum (hip socket) of the hip bone¹. Together they form the hip joint¹.

Below the head sits the femoral neck, a narrowed region¹. In the average adult, the neck meets the shaft at about 128 degrees². This angle gets smaller with age².

The greater trochanter (the bony bump at the outer hip) anchors several muscles that act across the hip¹. Because it sticks out from the bone, it gives those muscles extra leverage¹. The lesser trochanter is a small bump on the inner side, just below the neck¹. A single powerful muscle attaches there¹.

Because it sticks out from the bone, it gives those muscles extra leverage.

Down the shaft to the knee

The linea aspera is a rough ridge running down the back of the shaft¹. Many hip and thigh muscles attach along it in long, narrow strips¹. Another feature is the adductor tubercle². The back half of the adductor magnus (a large muscle on the inner side of the thigh) attaches there².

At the lower end are two condyles (rounded knobs where a bone meets another bone at a joint), one inner and one outer¹. They meet the tibia to form the knee joint¹. Beside them sit the epicondyles (bumps on the sides of the condyles)¹. They anchor muscles and the ligaments (tough bands that hold bones together at a joint) that support the knee¹.

At the front of the lower end is a smooth groove, the patellar surface¹. The patella (kneecap) sits in this groove and glides on it¹. This keeps the quadriceps tendon from rubbing on the lower femur¹.

The hip and knee sit at the two ends of the femur². Both are synovial joints (joints with a fluid-filled space between the bones, which lets them move freely)². Their surfaces are covered with cartilage (a firm, rubbery tissue, softer than bone), which reduces friction².

How much load passes through it

A review describes the upper femur as built to resist force in the direction of weight-bearing⁶. The same review describes it as less able to resist force from a sideways fall⁶. One study measured the force at the hip in four patients with instrumented hip implants (artificial hips that record the force through them)³.

Activity (four patients with instrumented hip implants)	Hip contact force (% of body weight)
Walking at about 4 km/h (average)3	2383
Going upstairs3	2513
Going downstairs3	2603

Breakdown

Hip fractures in older adults

A systematic review (a study that searches the research on a question in a checkable way) covered hip fracture rates in 63 countries⁷. It found more than a 10-fold difference in risk between countries⁷. A worldwide systematic review compared age-standardised rates (adjusted so groups with different age mixes can be compared fairly)⁷. Within countries, the rate in men was about half the rate in women⁷.

In one study of 206 consecutive hip fracture patients, 98% of the fractures came from a fall⁴. In that study, 76% said they fell straight to the side⁴. A fresh bruise over the greater trochanter was found in 56% of them, against 6% of fallers without a fracture⁴. A review describes sideways falls as raising neck fracture risk by loading the upper outer part of the neck⁶. It describes that part as relatively weak⁶.

After a hip fracture, studies report these outcomes^8,9:

• A meta-analysis of cohorts aged 50 and over found a 5- to 8-fold higher risk of death from any cause in the first 3 months⁸.
• The same meta-analysis found that extra yearly deaths persisted over time in older women and men, and were higher in men at any given age⁸.
• A review of cohort studies (which follow people over time) found that 40 to 60% of people regained their pre-fracture mobility⁹.
• That review found that most recovery of walking and daily activities took place within 6 months⁹.
• It also reports that in Western nations, 10 to 20% of patients move into institutional care (long-term living in a care home) after the fracture⁹.

Stress fractures of the femoral neck

An international consensus on bone stress injuries in athletes (a statement agreed by a panel of experts) describes them as overuse injuries to bone¹⁰. These include stress reactions (early bone stress injuries, before a crack forms) and stress fractures (small cracks from repeated load)¹⁰. A review describes femoral neck stress fractures as relatively rare¹¹. It says they most often affect military recruits and endurance athletes¹¹.

One systematic review pooled case reports (reports on single patients)¹². It found a sizable share in people with low activity and abnormal bone metabolism (the building and breakdown of bone)¹².

A review reports that a stress fracture here that is left untreated can progress to a complete, displaced break (bone ends moved out of line)¹¹. Such a break can be associated with nonunion (a break that fails to join) and long-term disability¹¹. It can also be associated with osteonecrosis (death of bone tissue) in the femoral head (the ball at the top of the thigh bone)¹¹.

A systematic review of bone stress injuries in athletes placed the femoral neck among the sites with the highest complication rates¹³. In the review of case reports, 71% of the 53 patients followed for at least a year returned to full pre-injury activity¹².

Breaks of the shaft

A population-based prospective study (a study that follows people forward in time) covered a region of 850,000 people¹⁴. It found femoral shaft fractures in 21 per 100,000 people a year¹⁴.

Recovery

How a broken bone mends

A review of fracture healing describes bone repair in general, not the femur alone¹⁵. It describes repair as rebuilding bone, repeating many of the steps by which the skeleton first forms before birth¹⁵. It reports that repair usually restores a bone’s structure and function¹⁵. It also reports that about 10% of fractures do not heal normally¹⁵.

How the femur responds to load

A review of bone mechanics reports that bone adapts to the loads it usually carries¹⁶. It adjusts its structure to the strain (how far something stretches as a share of its resting length) on it¹⁶. The review names the strain’s size, rate, frequency and spread¹⁶.

One modelling study (a study that estimates forces inside the body with a model rather than measuring them directly) looked at 15 activities¹⁷. In it, neck strain closely tracked the force at the hip joint¹⁷. Where the peak load fell depended on the activity¹⁷.

The study estimated that 8 of the 15 weight-bearing and resistance activities were likely to trigger bone formation in the neck¹⁷. Three activities produced the largest estimated increase in strain energy¹⁷. They were isokinetic hip extension (on a machine that holds the limb to a fixed speed), the one-legged long jump and isokinetic knee flexion¹⁷.

A review reports that the neck adapts to activity mainly in its lower inner, weight-bearing region⁶. It found little or no adaptation in the upper outer region⁶.

Studies in people report these findings^5,18:

• In a study of 24-year-old men, soccer players had 19.5% higher femoral neck bone density than non-athletic men of the same age¹⁸.
• In the same study, men who did nonspecific resistance exercise showed no higher bone density, and no better bone geometry (shape), than non-athletic men¹⁸.
• A meta-analysis of six studies in premenopausal women (before menopause) found that jumping exercise raised bone density at the femoral neck and trochanter¹⁹.
• A meta-analysis of trials lasting at least 6 months in postmenopausal women found a significant, low-to-moderate effect of dynamic resistance exercise on femoral neck density⁵.
• A meta-analysis of 10 randomised trials (studies that assign people to groups by chance) tested supervised exercise lasting 6 months or more²⁰. It found gains in lower-limb bone strength at loaded sites for children, but not for adults²⁰.

One study followed 14 crew members (13 men and 1 woman, aged 40 to 55) on 4- to 6-month space station missions²¹. Their hip bone density fell by 1.4 to 1.5% a month²¹.

Connections

Most muscles that attach to the femur and move it start on the pelvic girdle¹. At the hip, the femoral head fits into the acetabulum of the pelvis¹. Muscles attached to the femur include these:

• The gluteus maximus: its deeper fibres attach to the femur²².
• The gluteus medius: its tendon, one of the gluteal tendons, attaches to the greater trochanter at two sites^23,24.
• The gluteus minimus: its tendon attaches to the front of the greater trochanter^23,25.
• The hip adductors: they generally start on the pelvis, attach to the femur and adduct it (move it toward the body’s midline) at the hip^1,26.
• The hamstrings: the short head of the biceps femoris (a hamstring muscle on the outer back of the thigh) starts from the linea aspera²⁷. It crosses only the knee²⁷.
• The gastrocnemius: it arises from the two condyles of the femur²⁸.

The knee is the body’s largest joint, and all three of its joints involve the femur¹. One lies between the kneecap and the femur, and two lie between the condyles of the femur and the tibia¹. The patella forms a joint only with the femur, not with the tibia¹.

Sources

1. Betts JG, Young KA, Wise JA, Johnson E, Poe B, Kruse DH, Korol O, Johnson JE, Womble M, DeSaix P (2022). Anatomy and Physiology 2e. OpenStax. Link
2. Chang A, Breeland G, Black AC, Hubbard JB (2023). Anatomy, Bony Pelvis and Lower Limb: Femur.. StatPearls. PMID 30422577
3. Bergmann G, Deuretzbacher G, Heller M, Graichen F, Rohlmann A, Strauss J, Duda GN (2001). Hip contact forces and gait patterns from routine activities.. Journal of Biomechanics. doi:10.1016/s0021-9290(01)00040-9 PMID 11410170
4. Parkkari J, Kannus P, Palvanen M, Natri A, Vainio J, Aho H, Vuori I, Järvinen M (1999). Majority of hip fractures occur as a result of a fall and impact on the greater trochanter of the femur: a prospective controlled hip fracture study with 206 consecutive patients.. Calcified Tissue International. doi:10.1007/s002239900679 PMID 10441647
5. Shojaa M, von Stengel S, Kohl M, Schoene D, Kemmler W (2020). Effects of dynamic resistance exercise on bone mineral density in postmenopausal women: a systematic review and meta-analysis with special emphasis on exercise parameters.. Osteoporosis International. doi:10.1007/s00198-020-05441-w PMID 32399891
6. Fuchs RK, Kersh ME, Carballido-Gamio J, Thompson WR, Keyak JH, Warden SJ (2017). Physical Activity for Strengthening Fracture Prone Regions of the Proximal Femur.. Current Osteoporosis Reports. doi:10.1007/s11914-017-0343-6 PMID 28133707
7. Kanis JA, Odén A, McCloskey EV, Johansson H, Wahl DA, Cooper C, IOF Working Group on Epidemiology and Quality of Life (2012). A systematic review of hip fracture incidence and probability of fracture worldwide.. Osteoporosis International. doi:10.1007/s00198-012-1964-3 PMID 22419370
8. Haentjens P, Magaziner J, Colón-Emeric CS, Vanderschueren D, Milisen K, Velkeniers B, Boonen S (2010). Meta-analysis: excess mortality after hip fracture among older women and men.. Annals of Internal Medicine. doi:10.7326/0003-4819-152-6-201003160-00008 PMID 20231569
9. Dyer SM, Crotty M, Fairhall N, Magaziner J, Beaupre LA, Cameron ID, Sherrington C, Fragility Fracture Network (FFN) Rehabilitation Research Special Interest Group (2016). A critical review of the long-term disability outcomes following hip fracture.. BMC Geriatrics. doi:10.1186/s12877-016-0332-0 PMID 27590604
10. Hoenig T, Hollander K, Popp KL, Fredericson M, Kraus EA, Warden SJ, Tenforde AS, Bone Stress Injury Authorship Group (2025). International Delphi consensus on bone stress injuries in athletes. British journal of sports medicine. doi:10.1136/bjsports-2024-108616 PMID 39638438
11. Bernstein EM, Kelsey TJ, Cochran GK, Deafenbaugh BK, Kuhn KM (2022). Femoral Neck Stress Fractures: An Updated Review.. Journal of the American Academy of Orthopaedic Surgeons. doi:10.5435/JAAOS-D-21-00398 PMID 35077440
12. Yang K, Sambandam S, Yan MJ, Huo M (2023). Femoral neck stress fracture return to activity and the effect of metabolic dysfunction on recovery: A systematic review.. Journal of Orthopaedics. doi:10.1016/j.jor.2023.07.023 PMID 37545869
13. Hoenig T, Eissele J, Strahl A, Popp KL, Stürznickel J, Ackerman KE, Hollander K, Warden SJ, Frosch KH, Tenforde AS, Rolvien T (2023). Return to sport following low-risk and high-risk bone stress injuries: a systematic review and meta-analysis. British journal of sports medicine. doi:10.1136/bjsports-2022-106328 PMID 36720584
14. Enninghorst N, McDougall D, Evans JA, Sisak K, Balogh ZJ (2013). Population-based epidemiology of femur shaft fractures.. Journal of Trauma and Acute Care Surgery. doi:10.1097/TA.0b013e31828c3dc9 PMID 23694881
15. Einhorn TA, Gerstenfeld LC (2015). Fracture healing: mechanisms and interventions.. Nature reviews. Rheumatology. doi:10.1038/nrrheum.2014.164 PMID 25266456
16. Hart NH, Nimphius S, Rantalainen T, Ireland A, Siafarikas A, Newton RU (2017). Mechanical basis of bone strength: influence of bone material, bone structure and muscle action.. Journal of musculoskeletal & neuronal interactions. PMID 28860414
17. Martelli S, Kersh ME, Schache AG, Pandy MG (2014). Strain energy in the femoral neck during exercise.. Journal of Biomechanics. doi:10.1016/j.jbiomech.2014.03.036 PMID 24746018
18. Nilsson M, Ohlsson C, Mellström D, Lorentzon M (2013). Sport-specific association between exercise loading and the density, geometry, and microstructure of weight-bearing bone in young adult men.. Osteoporosis International. doi:10.1007/s00198-012-2142-3 PMID 23011682
19. Zhao R, Zhao M, Zhang L (2014). Efficiency of jumping exercise in improving bone mineral density among premenopausal women: a meta-analysis.. Sports medicine (Auckland, N.Z.). doi:10.1007/s40279-014-0220-8 PMID 24981245
20. Nikander R, Sievänen H, Heinonen A, Daly RM, Uusi-Rasi K, Kannus P (2010). Targeted exercise against osteoporosis: A systematic review and meta-analysis for optimising bone strength throughout life.. BMC Medicine. doi:10.1186/1741-7015-8-47 PMID 20663158
21. Lang T, LeBlanc A, Evans H, Lu Y, Genant H, Yu A (2004). Cortical and trabecular bone mineral loss from the spine and hip in long-duration spaceflight.. Journal of Bone and Mineral Research. doi:10.1359/JBMR.040307 PMID 15125798
22. Krause Neto W, Krause TLV, Gama EF (2025). The impact of resistance training on gluteus maximus hypertrophy: a systematic review and meta-analysis.. Frontiers in Physiology. doi:10.3389/fphys.2025.1542334 PMID 40276368
23. Pfirrmann CW, Chung CB, Theumann NH, Trudell DJ, Resnick D (2001). Greater trochanter of the hip: attachment of the abductor mechanism and a complex of three bursae--MR imaging and MR bursography in cadavers and MR imaging in asymptomatic volunteers.. Radiology. doi:10.1148/radiol.2211001634 PMID 11687692
24. Robertson WJ, Gardner MJ, Barker JU, Boraiah S, Lorich DG, Kelly BT (2008). Anatomy and dimensions of the gluteus medius tendon insertion.. Arthroscopy. doi:10.1016/j.arthro.2007.11.015 PMID 18237695
25. Philippon MJ, Michalski MP, Campbell KJ, Goldsmith MT, Devitt BM, Wijdicks CA, LaPrade RF (2014). Surgically Relevant Bony and Soft Tissue Anatomy of the Proximal Femur.. Orthopaedic Journal of Sports Medicine. doi:10.1177/2325967114535188 PMID 26535335
26. Jeno SH, Launico MV, Schindler GS (2023). Anatomy, Bony Pelvis and Lower Limb: Thigh Adductor Magnus Muscle.. StatPearls. PMID 30521263
27. Koolmees DS, Klott JD, Poppe TR, Bernholt DL (2025). Distal Hamstring Injuries and Disorders.. Journal of the American Academy of Orthopaedic Surgeons: Global Research & Reviews. doi:10.5435/JAAOSGlobal-D-25-00248 PMID 40972536
28. Bordoni B, Varacallo MA (2026). Anatomy, Bony Pelvis and Lower Limb: Gastrocnemius Muscle.. StatPearls. PMID 30422541

Every source the library cites

Changes

• September 30, 2026 First published.