Ankle joint

Function

Where the bones meet

The ankle joint is where the talus meets the lower ends of the tibia (shinbone) and the fibula (the thin outer lower-leg bone)^1,2. The tibia and fibula form a socket around the talus, called the mortise^1,2. The part where the talus meets the tibia carries body weight between the leg and the foot¹. The tibia’s lower end forms the medial malleolus (the bony bump on the inner side of the ankle)¹.

Experimental studies found about 83% of the load at the ankle passes between the tibia and talus³. The other 17% passes through the fibula, and more of it does so when the foot is pulled up³. The talus passes body weight and forces between the lower leg and the foot⁵. Yet no muscle attaches directly to it^3,5.

A review of ankle biomechanics describes an “ankle joint complex” of three joints³. Besides the ankle joint itself, they include the subtalar joint and one other joint of the foot³. The subtalar joint lies between the talus and the calcaneus (heel bone)^1,3.

A hinge, mostly

An anatomy textbook describes the medial malleolus and the lateral malleolus (outer ankle bone) holding the sides of the talus¹. This stops side-to-side motion, so the ankle works as a hinge¹. It allows only dorsiflexion (pulling the foot and toes up toward the shin) and plantar flexion (pointing the foot down)¹. The review of ankle biomechanics sees it differently³. The top of the talus is cone-shaped and the joint turns about a slanted axis, which suggests it may not be a simple hinge³.

The talus is widest at the front³. So the ankle is more stable when the foot is pulled up³. Turning the sole inward (inversion) and outward (eversion) happens mainly below the ankle, at the subtalar joint^1,3.

How far it moves

Studies put the ankle’s total up-and-down range at 65 to 75 degrees, varying between people³. That is 10 to 20 degrees of dorsiflexion and 40 to 55 degrees of plantar flexion³. Everyday tasks use much less of that range, at most about this much³:

Activity	Up-and-down range used, degrees
Walking	303
Climbing stairs	373
Going down stairs	563

What holds it together

Three groups of ligaments (tough bands of tissue that hold bones together at a joint) steady the ankle³:

Group	Where it sits	What it does
Lateral ankle ligaments	The outer side: the anterior and posterior talofibular and the calcaneofibular ligaments1	Support the ankle and resist too much inversion1
Deltoid ligament	The inner side, a broad ligament1	Supports the joint and resists too much eversion1
Syndesmosis	Just above the ankle, a strong fibrous link between the tibia and fibula1	Keeps the two bones from separating and the talus locked between them1

The calcaneofibular ligament is the only connective tissue that directly links the ankle joint and the subtalar joint³. While the foot is on the ground, the joint’s shape alone is enough to resist eversion³. Otherwise, its stability comes from the soft tissues around it³.

The loads it carries

The review of ankle biomechanics reports that the ankle complex carries about five times body weight while the foot is down in normal walking³. In activities such as running, it carries up to thirteen times body weight³. The bone surfaces fit closely, giving a large load-bearing area of 11 to 13 square centimetres³. Some have proposed that this means lower stress than in the hip or knee³.

In walking, the ankle makes its greatest power about halfway through each stride, as the calf muscles push the body forward³.

Breakdown

The most injured joint in many sports

A review gathered sports-injury studies from 38 countries, published from 1977 to 2005⁴. Across them, the ankle was the second most often injured body site, after the knee⁴. Sprain (a stretched or torn ligament) was its most common injury⁴. Among 70 sports, the ankle was the most often injured site in 24⁴.

A meta-analysis (a study that pools the results of several earlier studies) looked at 181 prospective studies (studies that follow people forward in time)⁶. Sprains were more frequent in females than males, and in children and adolescents than adults⁶. Indoor and court sports had the highest rate of any sport group, at 7 sprains per 1,000 exposures⁶. Sprains on the outer side were the most common type⁶. The ankle sprain page covers who has sprains and how they run their course.

How the ligaments give way

In an outer ankle sprain, the anterior talofibular ligament gives way first, and may be the only one hurt^7,8. The calcaneofibular ligament is most often next^7,8.

A high ankle sprain is a sprain of the ligaments that join the lower shinbone and fibula, just above the ankle joint⁹. An anatomy review reports that the weakest of them is the anterior inferior tibiofibular ligament⁹. It is the first to give way when the fibula is twisted outward⁹.

The biomechanics review says the tight binding of the lower tibia and fibula makes that joint highly prone to injury³. More on each group is on the lateral ankle ligaments, deltoid ligament and syndesmosis pages.

Damage to the talus

A consensus working group, a panel of experts, looked at cartilage-and-bone lesions (areas of damage) of the talus¹⁰. Most affect the inner or outer part of its top¹⁰. In one study it cites, an earlier injury came before 98% of outer lesions and 70% of inner ones¹⁰. Another study it reports found such lesions in 42% of 37 professional soccer players who had no symptoms¹⁰.

Osteoarthritis usually follows injury

Compared with the hip or knee, the ankle seems far less prone to osteoarthritis unless it has been injured before³. At two centres, most ankles with advanced arthritis had been injured before^11,12. The table compares injury-related cases with primary osteoarthritis (osteoarthritis that develops without a known earlier cause)^11,12:

Compared with the hip or knee, the ankle seems far less prone to osteoarthritis unless it has been injured before.

Centre	Ankles studied	Following an injury	Primary osteoarthritis
One US specialist centre	639 with advanced arthritis11	70%11	7%11
One other centre	406 with painful end-stage osteoarthritis12	78%12	9%12

At the US centre, the injury-related cases most often followed rotational (twisting) ankle fractures¹¹. At the other centre, people with injury-related osteoarthritis were younger than those with primary osteoarthritis¹².

A narrative review (a summary of research without a set search method) reports that outer ankle sprains lie behind 13% to 22% of ankle osteoarthritis¹³. It reports the same sprains lie behind 80% of injury-related ankle osteoarthritis¹³. It reports that injury-related ankle osteoarthritis may start younger than primary osteoarthritis, on average in people’s forties¹³.

A Korean national insurance cohort (a group of people followed over time) took in 195,393 people¹⁴. Those with a sprain had a 46% higher rate of later ankle osteoarthritis than those without¹⁴. A case series (a report on a group of patients, without a comparison group) studied 30 people with end-stage osteoarthritis after a ligament injury¹⁵. On average, it appeared 34.3 years after the injury¹⁵. It came sooner after a single severe sprain than after repeated injuries, at 25.7 against 38.0 years¹⁵.

Recovery

How the outer ligaments heal

A systematic review (a study that searches for research in a set, checkable way) looked at 7 randomised trials¹⁶. These trials assign people to groups by chance, and they measured ankle looseness after a fresh sprain¹⁶. It concluded that the outer ligaments needed 6 weeks to 3 months or more to heal¹⁶. Looseness improved over 6 weeks to 1 year¹⁶.

In two of the trial reports in that review, 3% to 31% of people still showed a sign of ligament looseness at 6 months¹⁶. Between 7% and 42% still felt the ankle was unstable up to a year after injury¹⁶.

Chronic ankle instability involves looseness and instability of the ankle that interfere with activity¹³. It can follow one sprain or repeated injuries to the outer ligaments¹³. One prospective cohort study found it in 40% of people a year after a first outer ankle sprain¹³. The lateral ankle ligaments page covers that tissue in more detail.

How the cartilage copes

In one study, 10 healthy adults had MRI scans (scans that show soft tissue in detail) before and after single-leg hopping¹⁷. The cartilage became measurably thinner, by about 3% on the tibia and 2% on the talus¹⁷.

A review compared cartilage in different joints¹⁸. Ankle articular cartilage holds more water and proteoglycans (large sugar-and-protein molecules in cartilage) than knee cartilage, and renews its proteoglycans faster¹⁸. These differences make it stiffer and less permeable, so fluid passes through it less easily¹⁸.

The same review reports that ankle cartilage cells respond less to breakdown signals than knee cartilage cells¹⁸. After damage, they make proteoglycans faster, which suggests a greater capacity for repair¹⁸.

The consensus working group concluded that talus lesions with few symptoms are unlikely to progress to ankle osteoarthritis¹⁰. It reports one study that followed 22 people with talus lesions for 11 to 20 years¹⁰. On X-ray, 73% of the cases assessed showed no worsening of osteoarthritis, and 27% worsened by one grade¹⁰. Also, 38% of the people had cut back on sport because of symptoms¹⁰.

Connections

The muscles and tendons that cross it

Most motion of the foot and ankle comes from twelve muscles that start in the lower leg and attach in the foot³. They sit in four compartments³:

• the gastrocnemius, soleus and plantaris at the back of the leg, which point the foot down³
• three deeper muscles at the back (tibialis posterior, flexor digitorum longus, flexor hallucis longus), which point the foot down and turn the sole in³
• the tibialis anterior, extensor digitorum longus, extensor hallucis longus and peroneus tertius at the front of the shin, which pull the foot up³
• the peroneus longus and peroneus brevis on the outer side, which point the foot down and turn the sole outward³

Judging by the force it can make, the authors of one dissection study consider the soleus likely the most important muscle acting at the ankle¹⁹. The gastrocnemius crosses two joints, the knee and the ankle^20,21. The superficial calf muscles all end on the Achilles tendon, which attaches to the heel bone¹. At the front, the tibialis anterior tendon belongs to the muscle that mainly lifts the foot and turns its sole inward²².

Exercises and stretches that load it

Related exercise pages: calf stretch, drop landing and single-leg squat. In 20 volunteers without symptoms, standing dorsiflexion averaged 25 degrees with the knee straight and 39 degrees with it bent 75 degrees²³. A systematic review of 6 studies suggests landing changes when dorsiflexion is restricted, though the studies disagree on which measures change²⁴. A meta-analysis of 21 studies found people with chronic ankle instability landed from a one-leg jump with more plantar flexion than controls²⁵.

One study followed 306 young basketball and floorball players for 12 months²⁶. Those whose knee angled far inward in a single-leg squat were 2.4 times more likely to injure an ankle²⁶.

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. Ficke J, Fakoya AO, Byerly DW (2026). Anatomy, Bony Pelvis and Lower Limb: Foot and Ankle. StatPearls. PMID 31536304
3. Brockett CL, Chapman GJ (2016). Biomechanics of the ankle.. Orthopaedics and Trauma. doi:10.1016/j.mporth.2016.04.015 PMID 27594929
4. Fong DT, Hong Y, Chan LK, Yung PS, Chan KM (2007). A systematic review on ankle injury and ankle sprain in sports.. Sports Medicine. doi:10.2165/00007256-200737010-00006 PMID 17190537
5. Khan IA, Varacallo MA (2023). Anatomy, Bony Pelvis and Lower Limb, Foot Talus. StatPearls. PMID 31082130
6. Doherty C, Delahunt E, Caulfield B, Hertel J, Ryan J, Bleakley C (2014). The incidence and prevalence of ankle sprain injury: a systematic review and meta-analysis of prospective epidemiological studies.. Sports Medicine. doi:10.1007/s40279-013-0102-5 PMID 24105612
7. Hertel J (2002). Functional Anatomy, Pathomechanics, and Pathophysiology of Lateral Ankle Instability.. Journal of Athletic Training. PMID 12937557
8. Golanó P, Vega J, de Leeuw PA, Malagelada F, Manzanares MC, Götzens V, van Dijk CN (2010). Anatomy of the ankle ligaments: a pictorial essay.. Knee Surgery, Sports Traumatology, Arthroscopy. doi:10.1007/s00167-010-1100-x PMID 20309522
9. Hermans JJ, Beumer A, de Jong TA, Kleinrensink GJ (2010). Anatomy of the distal tibiofibular syndesmosis in adults: a pictorial essay with a multimodality approach. Journal of anatomy. doi:10.1111/j.1469-7580.2010.01302.x PMID 21108526
10. Walther M, Gottschalk O, Madry H, Müller PE, Steinwachs M, Niemeyer P, et al (2023). Etiology, Classification, Diagnostics, and Conservative Management of Osteochondral Lesions of the Talus. 2023 Recommendations of the Working Group "Clinical Tissue Regeneration" of the German Society of Orthopedics and Traumatology.. Cartilage. doi:10.1177/19476035231161806 PMID 37082983
11. Saltzman CL, Salamon ML, Blanchard GM, Huff T, Hayes A, Buckwalter JA, Amendola A (2005). Epidemiology of ankle arthritis: report of a consecutive series of 639 patients from a tertiary orthopaedic center.. The Iowa Orthopaedic Journal. PMID 16089071
12. Valderrabano V, Horisberger M, Russell I, Dougall H, Hintermann B (2009). Etiology of ankle osteoarthritis.. Clinical Orthopaedics and Related Research. doi:10.1007/s11999-008-0543-6 PMID 18830791
13. Herzog MM, Kerr ZY, Marshall SW, Wikstrom EA (2019). Epidemiology of Ankle Sprains and Chronic Ankle Instability.. Journal of Athletic Training. doi:10.4085/1062-6050-447-17 PMID 31135209
14. Lee S, Song K, Lee SY (2022). Epidemiological study of post-traumatic ankle osteoarthritis after ankle sprain in 195,393 individuals over middle age using the National Health Insurance Database: A retrospective design.. Journal of Science and Medicine in Sport. doi:10.1016/j.jsams.2021.08.018 PMID 34565662
15. Valderrabano V, Hintermann B, Horisberger M, Fung TS (2006). Ligamentous posttraumatic ankle osteoarthritis.. The American Journal of Sports Medicine. doi:10.1177/0363546505281813 PMID 16303875
16. Hubbard TJ, Hicks-Little CA (2008). Ankle ligament healing after an acute ankle sprain: an evidence-based approach.. Journal of Athletic Training. doi:10.4085/1062-6050-43.5.523 PMID 18833315
17. Cher WL, Utturkar GM, Spritzer CE, Nunley JA, DeFrate LE, Collins AT (2016). An analysis of changes in in vivo cartilage thickness of the healthy ankle following dynamic activity.. Journal of Biomechanics. doi:10.1016/j.jbiomech.2016.05.030 PMID 27289415
18. Kuettner KE, Cole AA (2005). Cartilage degeneration in different human joints.. Osteoarthritis and Cartilage. doi:10.1016/j.joca.2004.11.006 PMID 15694570
19. Ward SR, Eng CM, Smallwood LH, Lieber RL (2009). Are current measurements of lower extremity muscle architecture accurate?. Clinical Orthopaedics and Related Research. doi:10.1007/s11999-008-0594-8 PMID 18972175
20. Pedret C, Palermi S, Mechó S, Frutos EJ, Rovira J, Vicente O, Balius R (2026). Calf Injuries: An Anatomy-Based Approach to Diagnosis, Management and Return to Sport.. Current reviews in musculoskeletal medicine. doi:10.1007/s12178-026-10059-2 PMID 42799963
21. Bryan Dixon J (2009). Gastrocnemius vs. soleus strain: how to differentiate and deal with calf muscle injuries.. Current reviews in musculoskeletal medicine. doi:10.1007/s12178-009-9045-8 PMID 19468870
22. Juneja P, Hubbard JB (2023). Anatomy, Bony Pelvis and Lower Limb: Tibialis Anterior Muscles.. StatPearls. PMID 30020676
23. Baumbach SF, Brumann M, Binder J, Mutschler W, Regauer M, Polzer H (2014). The influence of knee position on ankle dorsiflexion - a biometric study.. BMC musculoskeletal disorders. doi:10.1186/1471-2474-15-246 PMID 25053374
24. Mason-Mackay AR, Whatman C, Reid D (2017). The effect of reduced ankle dorsiflexion on lower extremity mechanics during landing: A systematic review.. Journal of science and medicine in sport. doi:10.1016/j.jsams.2015.06.006 PMID 26117159
25. Chan LYT, Sim YTN, Gan FK, Bin Abd Razak HR (2022). Effect of chronic ankle instability on lower extremity kinematics, dynamic postural stability, and muscle activity during unilateral jump-landing tasks: A systematic review and meta-analysis.. Physical therapy in sport : official journal of the Association of Chartered Physiotherapists in Sports Medicine. doi:10.1016/j.ptsp.2022.04.005 PMID 35462322
26. Räisänen AM, Pasanen K, Krosshaug T, Vasankari T, Kannus P, Heinonen A, Kujala UM, Avela J, Perttunen J, Parkkari J (2018). Association between frontal plane knee control and lower extremity injuries: a prospective study on young team sport athletes.. BMJ Open Sport & Exercise Medicine. doi:10.1136/bmjsem-2017-000311 PMID 29387448

Every source the library cites

Changes

• October 15, 2026 Revised. Corrects a statement that the gastrocnemius is the only lower-leg muscle crossing both the knee and the ankle.
• September 30, 2026 A supporting claim was narrowed to match its source; the page text is unchanged.