Femur: Anatomy, Functions, and Health of the Thigh Bone
Updated: 2 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026
Source currency note: This guide reflects medical information reviewed in March 2022. Always confirm current guidance with your healthcare professional.
Quick Answer: What is the femur?
The femur is the thigh bone and the longest and strongest bone in the body, running from the hip joint to the knee joint. It bears body weight, stabilizes movement and connects hip and knee muscles, tendons and ligaments. Fractures usually need severe trauma, but osteoporosis can weaken it, so good nutrition, exercise and checkups help protect it. [4]
What the research says
A hip fracture is very dangerous for frail older adults who do not have surgery. A systematic review and meta-analysis of 18 studies of frail older adults with a hip fracture who were managed without surgery, mostly for medical reasons, found pooled death rates of 36% at 30 days, 46% at 6 months, and 60% at 1 year. About one-third developed complications in hospital. The studies were of low to moderate quality (Loggers et al., Injury, 2020).
Exercise can improve bone density, including at the femoral neck. A network meta-analysis of 74 randomized trials (5,331 postmenopausal women and older women) found that exercise programs lasting 24 weeks or more improved bone mineral density. Combined programs, such as mind-body plus resistance exercise or multimodal exercise, helped the femoral neck (the part of the femur next to the hip joint), and programs lasting 52 weeks or longer gave more consistent gains (Zhou et al., Journal of Sport and Health Science, 2026).
Calcium and vitamin D supplements alone showed little to no fracture protection. A meta-analysis of 69 trials (153,902 adults, mostly living in the community and not at high risk) found little to no effect on the risk of any fracture from calcium (risk ratio 0.91; 95% CI 0.81 to 1.01), vitamin D (1.00; 95% CI 0.95 to 1.06), or both together (0.91; 95% CI 0.84 to 0.99), and the authors judged any benefit too small to matter. Evidence in high-risk people was limited, so ask your provider whether supplements make sense for you (Massé et al., BMJ, 2026).
Anatomy of the Femur
The femur is divided into three main sections: the proximal aspect, the shaft, and the distal aspect.
Proximal aspect (hip connection)
The upper end of the femur connects to the hip joint. This section includes the head, which fits into the hip socket, and the neck, a common site for fractures in older adults. It also has the greater and lesser trochanters, which serve as attachment points for major muscles.
The femoral shaft
The shaft is the long, cylindrical middle portion of the bone. It angles slightly toward the center of the body, which helps with balance and weight distribution. This part of the bone gives the structural strength needed to support your weight during physical activity.
Distal aspect (knee connection)
The lower end of the femur meets the tibia (shin bone) and the patella (kneecap) to form the knee joint. This section has rounded structures called condyles that allow smooth movement of the knee.
Feature | Description | Measurement or value |
Length | Total length of the bone in an average adult | About 18 inches |
Strength | Weight-bearing capacity | Up to 30 times body weight |
Location | Position in the body | Thigh (hip to knee) |
Essential Functions of the Femur
The femur does several critical jobs that make human movement and stability possible:
Weight support: it bears the weight of your body when you stand, walk, or run.
Stabilization: it provides a stable foundation for the lower body, which allows balance during complex movements.
Muscle attachment: it is a vital anchor for the muscles, tendons, and ligaments that control the hips and knees.
Circulatory support: it also supports parts of the circulatory system that pass through the thigh area.
Common Conditions and Disorders
Despite its strength, the femur can be affected by injuries and long-term health conditions. The most common are fractures, osteoporosis, and patellofemoral pain syndrome.
Femur fractures
A fracture is a break in the bone, usually caused by high-impact trauma such as a car accident or a significant fall. Symptoms include intense pain, swelling, and being unable to move the leg as you usually can. Fractures are medical emergencies and often need surgery and extensive physical therapy.
Osteoporosis
Osteoporosis is a condition that weakens bones, making them more likely to break suddenly and unexpectedly. It usually has no obvious symptoms until a fracture occurs. Females and adults older than 50 have a higher risk and should talk to their provider about a bone density screening.
Patellofemoral pain syndrome (PFPS)
Commonly known as runner's knee, this condition causes pain around or under the kneecap. It can be caused by overuse, new footwear, or sudden changes in activity level.
Caring for Your Femur
Keeping your bones strong is essential for preventing injuries and staying mobile for life.
Bone density testing: if you are older than 50 or have a family history of osteoporosis, talk to your provider about a DEXA scan, which measures bone strength.
Nutrition: aim for enough calcium and vitamin D, mainly through a balanced diet, and ask your provider whether supplements are right for you.
Weight-bearing exercise: regular physical activity helps maintain bone density and strengthens the muscles that support your bones.
Safety precautions: wear a seatbelt, use protective gear for sports and activities, and keep your home free of clutter and other trip hazards to prevent falls.
Conclusion
The femur is a remarkable structure that gives you the strength and stability for nearly every part of human movement. As the strongest bone in the body, it is built to handle significant stress, yet it still needs care and protection. By understanding its anatomy and the risks from conditions such as osteoporosis, you can take steps to protect your bone health and stay active throughout life.
Next step: If you are older than 50 or have a family history of bone problems, talk to your healthcare provider about a bone density screening to check your bone health.
Frequently Asked Questions
What is the femur?
The femur is the thigh bone, which is the longest and strongest bone in the human body.
Where is the femur located?
The femur is the only bone in the thigh, and it runs from the hip joint down to the knee joint.
How strong is the femur?
The femur is incredibly strong and can support as much as 30 times the weight of your body.
How long is the average adult femur?
Most adult femurs are about 18 inches long.
What are the symptoms of a femur fracture?
Common symptoms include severe pain, swelling, tenderness, bruising or discoloration, and being unable to move the leg or bear weight as you usually can. Go to the emergency room right away if you have had a trauma or think you have a fracture.
What is osteoporosis?
Osteoporosis is a condition that weakens bones, making them more likely to break unexpectedly.
Who is at risk for femur problems?
Females and adults older than 50 have a higher risk of osteoporosis and the fractures that can come with it. Serious trauma, such as a fall or car accident, is the usual cause of a femur fracture in people with healthy bones.
What is a DEXA scan?
A DEXA (or DXA) scan is a bone density test that uses low levels of X-rays to measure bone strength and track bone loss as you age.
What is runner's knee?
Runner's knee, or patellofemoral pain syndrome, is pain around or under the kneecap that is often caused by overuse.
How can I keep my femur healthy?
Eat a balanced diet with enough calcium and vitamin D, get regular weight-bearing exercise, see your provider for regular checkups, and follow safety tips to prevent falls and injuries.
Related Reading
Broken Femur (Femur Fracture): Types, Symptoms, Causes, Diagnosis, Treatment and Outlook — What You Need to Know explains the types of femur fractures and how they are treated.
Hip Fracture: Symptoms, Causes, and Treatment covers breaks at the top of the femur and recovery after surgery.
Osteoporosis: Causes, Symptoms, Diagnosis and Treatment Explained describes bone thinning that raises the risk of femur fractures.
Thigh Muscles: Anatomy, Essential Functions, and Care explains the muscles that attach to the femur and move the leg.
References
Loggers SAI, Van Lieshout EMM, Joosse P, et al. Prognosis of nonoperative treatment in elderly patients with a hip fracture: a systematic review and meta-analysis. Injury. 2020;51(11):2407-2413. PMID 32907702. https://doi.org/10.1016/j.injury.2020.08.027
Zhou Z, Wei X, Zhang X, et al. Effects of different types of exercise over 24 weeks on bone mineral density in postmenopausal women: a systematic review with pairwise and network meta-analysis of randomized controlled trials. Journal of Sport and Health Science. 2026;15:101127. PMID 41617082. https://doi.org/10.1016/j.jshs.2026.101127
Massé O, Mercurio CM, Dupuis S, et al. Calcium, vitamin D, or combined supplementation to prevent fractures and falls: systematic review and meta-analysis. BMJ. 2026;393:e088050. PMID 42161415. https://doi.org/10.1136/bmj-2025-088050
Cleveland Clinic. Femur (thighbone): anatomy, function and common conditions. Cleveland Clinic. March 11, 2022. https://my.clevelandclinic.org/health/body/22503-femur
Medical disclaimer
This article was prepared for general information only and is not a substitute for professional medical advice.
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