Ankle Joint: Anatomy, Joint Surfaces, Fibrous Capsule, Ligaments, Associated Injuries and Therapies

This part of the body absorbs the pressure that occurs when your feet touch the ground with each step you take.

Your ankles are the great negotiator between the ground and the rest of your body.

More than two dozen bones that make up your ankle and foot, and the three joints in your ankle, play a game of constant sensing to determine what type of terrain you are navigating and how to best move through it.

They also stabilize your body weight, which is simultaneously lowered through the narrow, right-angled frame of your ankles.

You probably don’t remember the constant work your ankles do, unless, of course, you are one of the 9 million Americans who sprain one each year.

While most ankle sprains occur when we are young (between the ages of 15 and 24), they are often not fully cured, leaving many of us with long-term mobility and stability issues.

The ankle has six different movements available:

  • Dorsiflexion : the top of the foot moves towards the knee.
  • Plantar flexion : the sole of the foot moves towards the calf.
  • Eversion : The outside of the ankle moves towards the hip.
  • Inversion : the inside of your ankle moves towards your groin.
  • Abduction : a movement in the ankle that causes the fingers to move away from the body.
  • Adduction : a movement in the ankle that causes the toes to move toward the midline.

When you combine dorsiflexion, eversion, and abduction, your foot is prone; When you combine plantar flexion, inversion, and adduction, your foot is supine.

Ankle anatomy

The ankle joint is medically known as the talocrural joint, it is a synovial joint that connects the distal ends of the tibia and fibula in the lower extremity with the proximal end of the talus.

Joints you should know

  • Talocrural – The technical term for the ankle joint, which is the point where the tibia, fibula, and talus meet.
  • The talocrural joint is the only mortise and tenon joint in the human body.
  • Transverse tarsal joint : where the talus, calcaneus, navicular and cuboid meet.
  • Subtalar joint : where the talus and calcaneus meet.

Knowing the major bones and joints of the lower leg and foot helps to better understand how the ankle moves:

Bones you should know

  • Tibia (shin bone) : the larger of the two bones that make up the lower leg.
  • Fibula – The thinnest and smallest bone on the outside of the lower leg.
  • Calcaneus : the heel bone.
  • Talus – a wedge-shaped bone of the ankle joint that lies between the heel bone and the fibula and tibia; forges a connection between the leg and the foot, aids in ankle movements, and helps maintain balance when weight is transferred from the ankle to the leg.
  • Metatarsals – A set of five long bones in the middle of the foot that connect the ankle to the toe.
  • Tarsal : a set of seven bones in the rear and middle foot that exist to help support weight; two of the most notable tarsals are the navicular and cuboid bones.
  • Navicular – A boat-shaped bone in the inner foot that creates the arch of the foot and helps with weight distribution.
  • Cuboid – A cube-shaped bone that connects and provides stability to the outer foot and ankle.

The ankle joint is maintained by the shape of the talus and its tight fit between the tibia and the fibula. In the neutral position, there are strong bone restrictions. Three bones make up this joint; the tibia, fibula, and talus.

Because movement of the subtalar joint provides a significant contribution to foot positioning, some authors describe it as the lower ankle joint and named the talocrural joint the upper ankle joint.

With increased plantar flexion, bone restrictions decrease and ligaments are more susceptible to stress and injury. The joint between the tibia and the talus carries more weight than that between the smaller fibula and the talus.

The ankle joint is a powerful joint that supports the weight of the lower limb. The ankle supports the weight of the whole body and also remains active in everyday life in many physical activities and also helps maintain body posture.

The weight of the body is transmitted from the tibia to the talus, which distributes the weight back and forth within the foot.

Your fibula, that long bone on the outside of your leg, is not bearing weight through your ankle. It only helps to form the lateral wall of the ankle joint.

The distances between the bones in the ankle are as follows:

  • Talus – maléolo medial: 1.70 ± 0.13 mm.
  • Talus – platillo tibial: 2.04 ± 0.29 mm.
  • Talus – maléolo lateral: 2.13 ± 0.20 mm.

Short distances indicate osteoarthritis .

As a region, the ankle is located at the junction of the leg and the foot. It extends downward (distally) from the narrowest point of the lower leg and includes the parts of the foot closest to the body (proximal) to the heel and the upper surface (back) of the foot.

The essential ligaments of the ankle joint are:

  • Capsular ligament.
  • Medial and lateral collateral ligaments.

Articular surfaces

The proximal articular outer layer of the ankle joint is made up of the articular facets of:

  • Lower end of the tibia consisting of its medial malleolus.
  • Lateral malleolus.
  • Inferior transverse tibioperoneal ligament.

Together these 3 create a deep tibiofibular socket (also called a ‘tibiofibular mortise’).

The distal articular outer layer of the ankle joint is composed of: articular facets in the superior, medial and lateral parts of the body of the talus.

The body of the talus has 3 articular surfaces:

  • Pulley-shaped superior articular surface (trochlear surface).
  • Articular surface in the form of a medial coma.
  • Lateral triangular articular surface.

The wedge-shaped body of the talus fits into the upper socket.

The articular surface on the underside of the lower end of the tibia articulates with the trochlear surface of the talus.

The articular surface on the lateral aspect of the medial malleolus articulates with the comma-shaped articular surface on the medial side of the talus.

The articular surface on the medial aspect of the lateral malleolus articulates with the entire large triangular articular surface on the lateral side of the body of the talus.

The ankle joint resembles a clamp or wrench that holds a portion of the hemisphere.

Fibrous capsule

Covers the joint completely. It is connected to the articular margins of the joint all around with 2 exceptions:

  • Posterosuperiorly it is connected to the inferior transverse tibioperoneal ligament.
  • Anteroinferiorly it is connected to the dorsum of the neck of the talus at some distance from the trochlear surface.

The joint capsule is thin in front and behind to allow for hinge movements and thick on both sides, where it combines with the collateral ligaments.

The synovial membrane lines the inner surface of the joint capsule, but ends at the periphery of the articular cartilages. A small synovial process goes up into the inferior tibiofibular syndesmosis.

Ankle joint strength

The trochlear surface in the superior aspect of the body of the talus is wider in front than behind.

During dorsiflexion, the ankle joint at the widest anterior part of the trochlea moves backward and properly conforms to the tibiofibular mortise (clamp), so the joint is stable.

During plantar flexion, the narrow posterior part of the trochlea does not fit properly into the tibiofibular mortise (clamp), making the joint unstable during plantar flexion.

Variables that maintain the strength of the ankle joint

  • Narrow interlocking of their articular surfaces.
  • Strong, medial and lateral collateral ligaments.
  • Deepening of the posterior tibiofibular socket by the inferior transverse tibiofibular ligament.
  • Tendons (4 in front and 5 behind) that cross the ankle joint.
  • Other ligaments of the joint.

There are four movements of your ankle: dorsiflexion, plantar flexion, inversion, and eversion. Various muscles come together near your ankle and help it move. Your ankle also has ligaments that attach one bone to another.

These ligaments help prevent excessive movement around the ankle joint. If you twist your ankle, one or more of these ligaments becomes overexcited, causing ankle pain and limited functional mobility.

Repeated ankle sprains can lead to an unstable ankle joint.

Ankle Ligaments

The ligaments of the ankle joint are grouped into two categories: the lateral collateral ligaments and the medial collateral ligaments.

Although the ankle ligaments are strong fibrous bands, they are often susceptible to injury due to excessive movement of the subtalar joint during activity.

Lateral collateral ligaments

The lateral collateral ligaments include the anterior talofibular ligament, the calcaneal-peroneal ligament, the talocal-cinnamon ligament, the posterior talo-calcaneal ligament, and the posterior talofibular ligament.

The anterior talofibular ligament passes from the tip of the lateral malleolus to the talus anteriorly. Limits plantar flexion of the joint. The calcaneal-fibular ligament passes from the lateral malleolus to the calcaneus with the calcaneus talus ligament at its base.

The posterior talofibular ligament passes from the tip of the lateral malleolus to the talus posteriorly. The posterior talocalcaneus extends this band to the calcaneus. Both limit dorsiflexion.

The lateral ankle ligaments are often twisted. If you turn your ankle inward forcefully, you can overstretch or tear these ligaments, which can lead to an ankle sprain.

Deltoid or medial ligament

The medial collateral ligaments, or deltoid ligament, include the tibionavicular ligament, the calcaneotibial ligament, the anterior talotibial ligament, and the posterior talotibial ligament.

The deltoid ligament is an extremely strong triangular ligament on the medial side of the ankle. It is divided into 2 parts: superficial and deep. Above, both parts have a common connection with the apex and margins of the medial malleolus.

Next, the connection of the superficial and deep parts differs as follows: Superficial part: its fibers are divided into 3 parts: anterior, middle and posterior.

The anterior fibers (tibionavicular) are connected to the tuberosity of the navicular bone and to the medial margin of the ligamentum of the spring.

The middle fibers (tibiocalcaneana) are connected to the entire length of the sustenculum tali. Posterior fibers (tibiotalar posterior) to the medial tubercle and adjacent part of the medial surface of the talus.

The deep part (tibiotalar anterior) is connected to the anterior part of the medial surface of the talus.

The tibionavicular ligament runs anteriorly from the medial malleolus to the navicular bone. The calcaneotibial ligament extends from the tip of the medial malleolus to the edge of the calcaneus.

The anterior and posterior talotibial ligaments extend anteriorly and posteriorly between the medial malleolus and the talus. They limit plantar flexion and dorsiflexion, respectively.

The fact that your fibula on the outside of your ankle blocks excessive movement toward eversion also creates a situation where overstretching the deltoid ligament is difficult.

Lateral ankle ligaments

Strengthen the joint laterally through three ligaments. These ligaments stabilize the ankle and serve as a guide to direct ankle motion by attaching the lateral malleolus to the bones below the ankle joint. They are responsible for resistance against inversion and internal rotation stress.

Physical therapy for a sprained ankle

If you’ve sprained or bent your ankle, you may have sprained your ankle. You can benefit from physical therapy for a sprained ankle.

Rehabilitation of an ankle sprain involves several components. These might be:

  • Control inflammation and swelling around your ankle.
  • Do exercises to improve your ankle range of motion.
  • Improve calf flexibility.
  • Improve ankle strength and stability.
  • Improve balance.
  • Improves proprioception of the lower limb.

Check with your doctor if you’ve sprained your ankle, just to make sure your ankle isn’t broken. Then visit your physical therapist to find out what to do to treat your sprained ankle. Your physical therapist can help you return to your previous activity level quickly and safely.

Ankle problems

The most common ankle injuries and problems include:


An ankle sprain is an injury to the ligaments outside the ankle, when the soft tissues are aggressively overexcited and the area swells into a state of repair.

Most sprains occur when the foot rolls inward (inversion). Depending on the severity of the sprain, it can take weeks to months to heal.

When an ankle is overworked too soon after a sprain, the tissues may not heal properly and may become permanently unstable and hypermobile, setting the stage for increased vulnerability to injury.


This is the loss of integrity of the ligament, and it is a common result of an ankle sprain. When the ankle ligaments have not healed from a previous injury, they can no longer do the job of supporting the ankle joint.

One sign that this may be the case is if you can hear the ankle “snap” or click. Hypermobility can lead to muscle weakness and hypertonia (having too much muscle tone), which can increase the risk of balance problems and injury.


Ankles can become stiff when their full range of motion is not used regularly, either as a result of an injury (such as a sprain) or simply from not moving enough.

High heels are also notorious for causing ankle stiffness.

The truth is that if you sit all day, or if you walk on flat surfaces instead of uneven or sloping terrain, there is a good chance that your ankles will not move through their full range of motion often enough. and as a result they can be limited.