Deltoid ligament

Function

Where it sits and what it joins

The deltoid ligament is the broad ligament on the inner (medial) side of the ankle joint¹. It is also called the medial collateral ligament of the ankle⁴. It runs from the medial malleolus (the bony bump on the inner side of the ankle) to the talus, calcaneus and navicular⁵. The talus is the ankle bone under the shinbone, the calcaneus is the heel bone and the navicular is a bone of the inner midfoot⁵.

The ligament spans three joints: the ankle (tibiotalar) joint, the subtalar joint and the talonavicular joint (between the talus and the navicular)⁴. The subtalar joint lies between the talus and the heel bone, where the sole turns inward and outward^1,6. The deltoid ligaments are one of three ligament groups that steady the ankle⁶. The other two are the lateral ligaments on the outer side and the syndesmosis⁶. The syndesmosis lies between the tibia (the shinbone) and fibula (the thin outer bone of the lower leg)⁶.

Two layers, six bands

A review of the research on its anatomy concluded that the only real agreement is that it has two layers, one superficial and one deep². The accepted description splits it into six bands, four superficial and two deep². In a cadaver (body donated for study) study of 10 ankles, the bands started from the front and back of the medial malleolus⁷.

A review of the research on its anatomy concluded that the only real agreement is that it has two layers, one superficial and one deep.

Some bands are missing in some ankles². A meta-analysis (a study that pools the results of several earlier studies) of 8 studies covered 142 ankle specimens⁸. It found each band in this share of ankles⁸:

Band	Layer	Ankles where found, %
Deep posterior tibiotalar	Deep	1008
Tibiospring	Superficial	about 948
Tibionavicular	Superficial	about 908
Tibiocalcaneal	Superficial	858
Superficial posterior tibiotalar	Superficial	about 808
Deep anterior tibiotalar	Deep	about 638

What the bands look like

One cadaver study of 10 ankles traced where the bands attach⁷:

• the tibionavicular band is the most forward part of the superficial layer, fanning down to the upper inner navicular⁷
• the tibiospring band runs from the front of the medial malleolus to the spring ligament (a ligament under the inner arch)⁷
• the tibiocalcaneal band attached to the sustentaculum tali, a shelf on the heel bone, in all 10 ankles studied⁷
• the deep posterior tibiotalar band was the thickest and largest band in all 10 ankles, over 3 mm thick⁷

In dissection, two tendons had to be moved aside to reach the ligament beneath⁷. They belong to the tibialis posterior (a deep calf muscle) and flexor digitorum longus (long toe flexor)⁷.

What each layer holds

The ligament supports the ankle and resists too much eversion of the foot¹. There is consensus that the deep layer is the main stabiliser of the ankle joint itself⁷. The superficial layer mainly steadies the subtalar and talonavicular joints⁷. The superficial layer limits eversion of the back of the foot⁴. The deep layer limits outward turning of the talus and its sliding forward, backward and sideways⁴.

Two sources describe how the two layers share the work of stopping the talus tilting into valgus (outward)^5,9. One cadaver study found the deltoid ligament the main restraint against this tilt, with its two layers equally effective⁹. An expert review states that the ankle tilts into valgus only when both layers are torn⁵. The same cadaver study suggested the deep layer is a backup restraint against sideways and forward talus movement⁹. In that study, the outer ankle bone and its ligaments were the main restraint⁹.

How foot position changes the load

The ligament is triangular and widens downward². So its front part is tight when the foot points down, and its back part is tight when the foot pulls up². A cadaver study of 10 ankles fits this: the tibiospring band was tense in plantar flexion (pointing the foot down)⁷. The tibiocalcaneal and deep posterior tibiotalar bands were tense in dorsiflexion (pulling the foot up toward the shin)⁷.

What happens when it is cut in the lab

Robotic cadaver studies cut the ligament, or parts of it, and measured the extra movement^10,11:

What was cut, and where	Extra movement
The whole ligament, 10 ankles	7.6 mm forward sliding, 13.8 degrees outward rotation, 33.6 degrees eversion10
The front part, 10 ankles, foot pointed down 25 degrees	2.1 degrees outward rotation, 6.2 degrees eversion10
The back part, same 10 ankles	No added looseness10
Superficial posterior tibiotalar band, 8 legs, foot up	3.3 degrees eversion11
Tibiocalcaneal band, 8 legs, foot down	4.2 degrees eversion11

Blood supply

In a cadaver study of 64 legs, three arteries sent branches to the ligament¹². The medial tarsal artery did so in 96.7%, the posterior tibial artery in 95% and the anterior tibial artery in 38.3%¹². In a cadaver study, every specimen also had blood supply entering through bone at the medial malleolus or the inner talus¹².

Breakdown

How it gets hurt

The main way it is injured is eversion of the ankle, with or without outward rotation². Typically this happens when a pronated foot (rolled inward so the arch lowers) lands on uneven ground². A foot rolled outward with the talus twisting outward can also injure it, often along with the syndesmosis².

One type of ankle fracture comes from an outward-twisting movement⁷. A cadaver study suggested that in it, the tibionavicular, tibiospring and deep anterior tibiotalar bands are at risk⁷. It suggested the tibiocalcaneal and especially the deep posterior tibiotalar bands are protected⁷. One video case report linked a non-contact inner ankle sprain to the foot pulled up at ground contact with rapid eversion¹³. Most tears happen where the ligament attaches to the medial malleolus⁵.

How often, and in whom

Most ankle sprains injure the outer ligaments². One review reports estimates of deltoid involvement in about 5% of ankle sprains². It adds that 3% to 4% of all ankle ligament injuries involve the deltoid ligament alone². Among cadets at the United States Military Academy, inner ankle sprains were 5.1% of ankle sprains¹⁴. Their incidence (new cases over a set time) was 3.5 per 1,000 person-years¹⁴.

In the same cadets, men were about three times as likely as women to have an inner ankle sprain¹⁴. Sport caused 64% of them, and the rate was highest in men’s rugby and gymnastics¹⁴.

A US college sports injury database recorded 380 deltoid ligament sprains across 25 sports from 2009-10 to 2014-15³. That was 0.79 sprains per 10,000 athlete-exposures, each being one athlete taking part in one practice or game³. Rates were highest in these sports, though the gymnastics figure is an imprecise estimate³:

Sport	Sprains per 10,000 athlete-exposures
Women’s gymnastics	2.303
Men’s soccer	1.733
Women’s soccer	1.613
Men’s football	1.403

In those college athletes, 49.7% of deltoid sprains came from contact with another player³. Another 19.5% involved no contact, and 18.7% came from contact with the playing surface³. Most happened in practice, but the rate in competition was 3.74 times the practice rate³.

Injured alongside other structures

The deltoid ligament is often hurt together with other parts of the ankle^2,15:

• Up to 40% of ankle fractures are estimated to include a deltoid injury²
• In one arthroscopy (keyhole surgery inside a joint) study of 288 people with fresh ankle fractures, 39.6% had one²
• In an MRI (a scan that shows soft tissue in detail) study of 110 athletes with fresh outer ligament injuries, 18 also had one¹⁵
• Unstable injuries of the syndesmosis can occur with a deltoid injury, and the severity of each varies widely⁵

A systematic review (a study that searches for all the research on a question in a set, checkable way) looked at 14 lab studies¹⁶. In three, a deltoid injury alone significantly changed how the syndesmosis moved¹⁶.

A systematic review of 9 studies looked at people with chronic ankle instability¹⁷. MRI showed deltoid injuries in 289 of 465 people scanned, 62%¹⁷. Where the layer was named, the deep layer was involved in 146 people and the superficial layer in 61¹⁷.

In 169 freshly sprained ankles without a fracture, 48 were tender over the deltoid ligament¹⁸. Ultrasound (a scan made with sound waves) confirmed deltoid damage in 13¹⁸. Of those, 3 were superficial only, 3 were deep only and 7 involved both layers¹⁸.

Recovery

Time lost in college athletes

In the US college database, 72.9% of deltoid sprains limited participation for under a week³. In 39.5%, the limit lasted under 24 hours³. In 6.6%, the sprain was severe, meaning more than 21 days lost or a season ended³. In the same athletes, 8.2% of sprains were repeat injuries, and 2 of 380 led to surgery³.

A slower course in one man

One case report followed a recreationally active man who sprained the deltoid ligament playing basketball¹⁹. Up to 5 months later, he still had reduced ankle movement and changed nerve responses in the soleus (a wide, flat calf muscle)¹⁹. He also had poorer balance and self-reported function, and had cut back his activity¹⁹.

How ligaments heal

Tendon and ligament healing is described in three phases: inflammatory, proliferative and remodelling²⁰. A review of knee ligament research describes injured ligament regaining function through scar tissue²¹. That scar is weaker, biologically and mechanically, than the tissue it replaces²¹. That review studied the ACL (a ligament that crosses inside the knee) and the MCL (the ligament on the inner side of the knee)²¹. It did not study the deltoid ligament²¹.

When injuries are left alone

One review states that neglected deltoid ligament injuries can lead to a worsening deformity². It names problems with the tibialis posterior tendon, flat foot and a back of the foot angled outward². It reports osteoarthritis (a disease in which joint cartilage wears away) after injury in 20.4% of one group². That group had an untreated deltoid injury alone².

The same review found no long-term studies of how often instability follows a deltoid injury². It called the evidence on deltoid injuries limited overall². Most ankle sprains injure the outer ligaments instead, as the ankle sprain page describes².

Connections

The joint and bones it holds

The deltoid ligament steadies the inner side of the ankle joint, alongside the outer ligaments and the syndesmosis⁶. It starts on the medial malleolus at the lower end of the tibia⁵. It ends on the talus, heel bone and navicular⁵.

The other ankle ligaments

The lateral ankle ligaments on the outer side are injured in most ankle sprains². The ankle syndesmosis lies between the tibia and fibula⁶. Outward-twisting injuries can hurt it and the deltoid ligament together².

The spring ligament and tibialis posterior

The tibiospring band joins the deltoid ligament to the spring ligament⁵. Part of the spring ligament is so tightly attached that the two are hard to separate in dissection⁴. This link is described as fundamental for keeping the foot aligned⁵. With the tibialis posterior tendon as a second, muscle-driven support, this inner group helps hold up the inner arch⁵.

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. Koris J, Calder JDF, Dalmau-Pastor M, Fernandez MA, Ramasamy A (2024). Deltoid ligament injuries: A review of the anatomy, diagnosis and treatments.. Knee Surgery, Sports Traumatology, Arthroscopy. doi:10.1002/ksa.12274 PMID 38796726
3. Kopec TJ, Hibberd EE, Roos KG, Djoko A, Dompier TP, Kerr ZY (2017). The Epidemiology of Deltoid Ligament Sprains in 25 National Collegiate Athletic Association Sports, 2009-2010 Through 2014-2015 Academic Years.. Journal of Athletic Training. doi:10.4085/1062.6050-52.2.01 PMID 28318315
4. Bilyy A, Win Mar WW, Al Abdeen Al Zuabi Z, Frimpong-Manso HB, Famure S, Solomou G, Brassett C, Pasapula C (2025). The Deltoid-Spring Ligament Complex: A Scoping Review and New Segmental Classification.. Cureus. doi:10.7759/cureus.81715 PMID 40322447
5. Fleury C, Acker A, Dubois-Ferrière V, Assal M (2026). Deltoid ligament injury: thinking beyond the ankle - an expert opinion.. EFORT Open Reviews. doi:10.1530/EOR-2025-0268 PMID 42684953
6. Brockett CL, Chapman GJ (2016). Biomechanics of the ankle.. Orthopaedics and Trauma. doi:10.1016/j.mporth.2016.04.015 PMID 27594929
7. Gregersen MG, Fagerhaug Dalen A, Nilsen F, Molund M (2022). The Anatomy and Function of the Individual Bands of the Deltoid Ligament-and Implications for Stability Assessment of SER Ankle Fractures.. Foot & Ankle Orthopaedics. doi:10.1177/24730114221104078 PMID 35722175
8. Yammine K (2017). The Morphology and Prevalence of the Deltoid Complex Ligament of the Ankle.. Foot & Ankle Specialist. doi:10.1177/1938640016675409 PMID 27807288
9. Harper MC (1987). Deltoid ligament: an anatomical evaluation of function.. Foot & Ankle. doi:10.1177/107110078700800104 PMID 3623356
10. Brady AW, Bryniarski A, Brown JR, Waltz R, Stake IK, Kreulen CD, Haytmanek CT, Clanton TO (2023). The Biomechanical Role of the Deltoid Ligament on Ankle Stability: Injury, Repair, and Augmentation.. The American Journal of Sports Medicine. doi:10.1177/03635465231181082 PMID 37449714
11. Takahashi K, Teramoto A, Murahashi Y, Shiwaku K, Kamiya T, Emori M, Watanabe K, Fujie H (2025). The In Situ Force and Contribution of Each Ligamentous Band of the Deltoid Ligament in Ankle Joint Stability: A Cadaveric Biomechanical Study.. Orthopaedic Journal of Sports Medicine. doi:10.1177/23259671251327406 PMID 40182569
12. Haynes JA, Gosselin M, Cusworth B, McCormick J, Johnson J, Klein S (2017). The Arterial Anatomy of the Deltoid Ligament: A Cadaveric Study.. Foot & Ankle International. doi:10.1177/1071100717702464 PMID 28447855
13. Wade FE, Mok KM, Fong DT (2018). Kinematic analysis of a televised medial ankle sprain.. Asia-Pacific Journal of Sports Medicine, Arthroscopy, Rehabilitation and Technology. doi:10.1016/j.asmart.2018.02.001 PMID 29963372
14. Waterman BR, Belmont PJ Jr, Cameron KL, Svoboda SJ, Alitz CJ, Owens BD (2011). Risk Factors for Syndesmotic and Medial Ankle Sprain. The American Journal of Sports Medicine. doi:10.1177/0363546510391462 PMID 21289274
15. Kim JS, Kim MS, Kim DK, Lee SH (2023). Magnetic Resonance Imaging Characteristics of a Lateral Ligament Injury in Acute Ankle Sprains Among Athletes.. Orthopaedic Journal of Sports Medicine. doi:10.1177/23259671231207688 PMID 37954866
16. Spennacchio P, Seil R, Gathen M, Cucchi D (2021). Diagnosing instability of ligamentous syndesmotic injuries: A biomechanical perspective. Clinical biomechanics (Bristol, Avon). doi:10.1016/j.clinbiomech.2021.105312 PMID 33756400
17. Anderson A, McLellan M, Kim R, Noori N (2025). Diagnosis and Management of Deltoid Ligament Injuries in Chronic Ankle Instability: A Systematic Review.. Foot & Ankle Orthopaedics. doi:10.1177/24730114251323903 PMID 40144531
18. Omodani T, Takahashi K (2023). Ultrasound findings of the deltoid ligament in patients with acute ankle sprains: A retrospective review.. Journal of Orthopaedic Science. doi:10.1016/j.jos.2022.05.010 PMID 35691876
19. Terada M, Thomas AC, Pietrosimone B, Hiller CE, Bowker S, Gribble PA (2015). The Consequence of a Medial Ankle Sprain on Physical and Self-reported Functional Limitations: A Case Study Over a 5-Month Period.. The Journal of Orthopaedic and Sports Physical Therapy. doi:10.2519/jospt.2015.6097 PMID 26304642
20. Leong NL, Kator JL, Clemens TL, James A, Enamoto-Iwamoto M, Jiang J (2020). Tendon and Ligament Healing and Current Approaches to Tendon and Ligament Regeneration.. Journal of Orthopaedic Research. doi:10.1002/jor.24475 PMID 31529731
21. Frank CB (2004). Ligament structure, physiology and function. Journal of musculoskeletal & neuronal interactions. PMID 15615126

Every source the library cites

Changes

• September 30, 2026 A supporting claim was narrowed to match its source; the page text is unchanged.