Joints and Ligaments of the Foot
The foot is the region of the body distal to the leg that is involved in weight bearing and locomotion. It consists of 28 bones, which can be divided functionally into three groups, referred to as the tarsus, metatarsus and phalanges. The foot possess 31 joints in total. These include the:
This article will discuss these joints, detailing their articular surfaces, the ligaments that stabilise them, and the muscles that produce movement at these joints. This will be followed by clinically relevant notes of common pathologic conditions affecting these structures.
The ankle joint, also known as the talocrural joint, is a hinge joint that involves the tibia and fibula of the leg and the talus of the foot. The body of the talus sits within a deep recess referred to as the mortise. This mortise is formed by the:
- Medial malleolus of the tibia
- Lateral malleolus of the fibula
- Inferior aspect of the tibia
The ankle joint is uniaxial and allows both dorsiflexion and plantar flexion. The range of dorsiflexion is 10 degrees when the knee is straight and can increase to approximately 30 degrees when the knee is flexed. The normal range of plantar flexion is about 30 degrees.
The articular surfaces involved in the ankle joint are covered by hyaline cartilage. The talar articulating surface for the tibial medial malleolus is flat and comma shaped, whereas the articulating surface for the lateral malleolus of the fibula is concave and triangular. The articulating surface for the inferior tibia is convex in the parasagittal plane but slightly concave transversely. These articulations are held together by a fibrous capsule and by the medial and lateral collateral ligaments.
Medial Collateral Ligament
The medial collateral ligament, also known as the deltoid ligament, is a triangular band that attaches to the medial malleolus proximally and to the talus and navicular bone distally. The ligament consists of four main groups of fibres:
- The tibionavicular fibres (anterior segment)
- The tibiocalcaneal fibres (intermediate segment)
- The anterior tibiotalar fibres (deep segment)
- The posterior tibiotalar fibres (posterior segment)
The tendons of the tibialis posterior and flexor digitorum longus cross this ligament.
Lateral Collateral Ligament
The lateral collateral ligament consists of three separate ligaments:
- The anterior talofibular ligament
- The posterior talofibular ligament and;
- The calcaneofibular ligament
As the name suggests, the anterior talofibular ligament connects the talus with the lateral malleolus of the fibula. It extends from the anterior aspect of the malleolus to the lateral surface of the talar neck. The posterior talofibular ligament runs horizontally from the distal aspect of the fibular malleolus to the lateral tubercle of the posterior process of the talus. The calcaneofibular ligament is a long cord that runs from a depression anterior to the fibular malleolus to a tubercle on the lateral aspect of the calcaneus.
Occasionally, it is also supplied by the superficial fibular nerve.
The tibialis anterior allows dorsiflexion at the ankle joint and is assisted by the tendons of the fibularis tertius, hallucis longus and extensor digitorum longus.
The soleus and gastrocnemius muscles allow plantar flexion with assistance from the tibialis posterior, flexor hallucis longus, plantaris and flexor digitorum longus muscles.
Inferior (Distal) Tibiofibular Joint
The inferior, or distal, tibiofibular joint is a syndesmosis, a slightly mobile, fibrous joint joined together with connective tissue.
It consists of three separate ligaments:
- The anterior tibiofibular ligament
- The posterior tibiofibular ligament
- The interosseus tibiofibular ligament
The anterior tibiofibular ligament is a flat band that descends between the tibia and fibula anterior to the syndesmosis. The posterior tibiofibular ligament descends posteriorly to the syndesmosis between the tibia and fibula. The distal part of this ligament, the inferior transverse ligament, is a yellow band that connects the medial and lateral malleoli. The interosseus tibiofibular ligament is a continuation of the interosseus membrane and is the strongest of the three ligaments.
The inferior tibiofibular joint is innervated by branches of the deep fibular and sural nerves.
No muscles act on this joint.
The subtalar joint consists of anterior and posterior articulations between the talus and calcaneus. The posterior articulation is referred to as the talocalcaneal joint.
This joint is stabilised by a fibrous capsule and four ligaments:
- The medial talocalcaneal ligament
- The lateral talocalcaneal ligament
- The interosseus talocalcaneal ligament
- The cervical ligament
The medial talocalcaneal ligament connects the medial tubercle of the talus with the substentaculum tali, a horizontal eminence on the calcaneus. The lateral process of the talus is connected to the lateral aspect of the calcaneus by the lateral talocalcaneal ligament. The interosseus talocalcaneal ligament runs between the sulcus tali, a groove on the inferior aspect of the talus, and the calcaneus sulcus. The cervical ligament ascends from the superior calcaneal surface to the inferolateral tubercle on the talar neck.
The talocalcaneal joint is innervated by branches of the sural, medial plantar and posterior tibial nerves.
The tibialis anterior, tibialis posterior, gastrocnemius and soleus muscles contribute together to perform heel inversion (movement of the sole of the foot towards the midline).
Eversion (movement away from the midline) results from the action of the fibularis longus, tertius and brevis muscles.
The talocalcaneonavicular joint consists of two articulations: the anterior articulation of the subtalar joint and the articulation between the talus and the navicular, the talonavicular joint.
These two articulations are stabilised by a fibrous capsule and by the talonavicular and plantar calcaneonavicular ligaments. The calcaneonavicular part of the bifurcate ligament also helps to stabilise this joint.
The talonavicular ligament is a thin band connecting the dorsal aspect of the talar neck with the navicular bone and is covered by extensor tendons. The plantar calcaneonavicular ligament, also known as the spring ligament, runs from the anterior aspect of the sustentaculum tali to the plantar surface of the navicular bone.
The innervation of the talocalcaneonavicular joint is provided by the medial plantar and deep fibular nerves.
The muscles producing the movement of this joint are the same as the talocalcaneal joint.
The calaneocuboid joint is a saddle (biaxial) joint, and is formed by the distal surface of the calcaneus and the proximal aspect of the cuboid.
The three ligaments that stabilise this joint are:
- The bifurcate ligament
- The long plantar ligament
- The plantar calcaneocuboid ligament
The bifurcate ligament is a Y-shaped band, which attaches proximally to the anterior aspect of the calcaneus. Distally, it divides into two parts: the calacaneocuboid and the calcaneonavicular parts. The calcaneocuboid part attaches to the dorsomedial surface of the cuboid bone whilst the calcaneonavicular part attaches to the dorsolateral aspect of the navicular bone.
The longest ligament associated with the tarsus is known as the long plantar ligament. It runs from the plantar surface of the calcaneus bone to the tuberosity located on the plantar aspect of the cuboid bone. More superficial fibres continue on to attach to the bases of the second to fourth metatarsals.
The plantar calcaneocuboid ligament is located deep to the long plantar ligament and is separated from it by areolar tissue. It extends from the anterior tubercle of the calcaneus to the plantar aspect of the cuboid.
Innervation of the calcaneocuboid joint is provided by the lateral plantar nerve (plantar aspect), sural and deep fibular nerves (dorsally).
The muscles producing movement of this joint are the same ones that act on the talocalcaneal and talocalcaneonavicular joints, aiding in the gliding and rotational movements between the calcaneus and cuboid bones.
The naviculocuneiform joint is a compound joint and consists of articulations between the navicular and the three cuneiform bones.
Two ligaments help form connections between these bones: the dorsal ligaments and the plantar ligaments.
The dorsal and plantar ligaments connect the navicular bone with each cuneiform. The medial dorsal ligament continues as a capsule around the medial aspect of the joint.
Innervation of the naviculocuneiform joint is provided by the deep fibular (dorsally), medial and lateral plantar nerves (plantar surface).
Slight gliding and rotation occurs at this joint. These movements are produced by the action of the fibularis longus and brevis, tibialis anterior and tibialis posterior muscles. The long extensors and flexors of the toes also contribute to the production of these movements.
The cuboideonavicular joint is a syndesmosis that connects the cuboid and navicular bones.
This joint is stabilised by dorsal, plantar and interosseus ligaments.
The muscles that produce movement of this joint are the same as the naviculocuneiform joint.
Intercuneiform And Cuneocuboid Joints
The intercuneiform and cuneocuboid joints are synovial joints involving the cuneiform and cuboid bones.
The bones are connected together by dorsal, plantar and interosseus ligaments.
Both the dorsal and plantar ligaments consist of three transverse bands, which run between the cuneiform bones and between the lateral cuneiform and the cuboid bone. The interosseus ligaments connect non-articular surfaces of the bones.
The innervation of these two joints is from the deep fibular nerve (dorsally), medial and lateral plantar nerves (plantar surface).
The muscles that produce movement of these joints are the same as those for the the naviculocuneiform joint.
The metatarsals form articulations with some of the tarsal bones of the foot to form the tarsometatarsal joints. The first metatarsal articulates with the medial cuneiform, the second with the intermediate cuneiform and the third metatarsal articulates with the lateral cuneiform. The lateral cuneiform also articulates with the fourth metatarsal and the cuboid bone forms articulations with both the fourth and fifth metatarsals.
There are three bands of ligaments involved in stabilising these joints:
- The dorsal tarsometatarsal ligaments
- The plantar tarsometatarsal ligaments and;
- The interosseus cuneometatarsal ligaments
Eight dorsal tarsometatarsal ligaments connect the metatarsal bones to the cuboid and cuneiform bones. These ligaments form the following connections:
- First metatarsal to the medial cuneiform
- Second metatarsal to each cuneiform
- Third metatarsal to the lateral cuneiform
- Fourth metatarsal to the lateral cuneiform and cuboid
- Fifth metatarsal to the cuboid
The plantar tarsometatarsal ligaments consist of both longitudinal and oblique bands.
The strongest of the three interosseus cuneometatarsal ligaments is the Lisfranc’s ligament. It runs from the second metatarsal to the lateral aspect of the medial cuneiform. The other two ligaments connect the lateral cuneiform with the second metatarsal and the lateral cuneiform with the base of the fourth metatarsal.
The innervation of the tarsometatarsal joints is from the deep fibular nerve (dorsally), medial and lateral plantar nerves (plantar surface).
Flexion and extension at the level of tarsometatarsal joints are produced by the short and long extensors and flexors of the toe.
Abduction and rotation can also occur at the first tarsometatarsal joint and are carried out by the tibialis anterior and fibularis longus muscles.
The intermetatarsal joints are articulations formed between the metatarsal bones and are stabilised by intermetatarsal interosseus ligaments. These ligaments run between the lateral four metatarsal bones. Dorsal and plantar intermetatarsal ligaments are also involved in the stabilisation of this joint.
The metatarsophalangeal joints are ellipsoid joints, which consist of articulations between the heads of the metatarsals and the bases of the proximal phalanges. On the plantar surface of the first metatarsal head, there are two longitudinal grooves separated by a ridge, the crista. These two grooves articulate with the two sesamoid bones within the joint capsule.
The sesamoid bones are connected together by the intersesamoid ligament. Other ligaments that stabilise the metatarsophalangeal joints include the:
- Plantar ligaments
- Deep transverse metatarsal ligaments
- Collateral ligaments
The thick plantar ligaments lie between the collateral ligaments, are attached firmly to the phalangeal bases and loosely to the metatarsal heads. They blend with both the deep transverse metatarsal and collateral ligaments.
Four flat bands, the deep transverse metatarsal ligaments, unite the plantar ligaments and lie between the interossei and the lumbricals.
The collateral ligaments run from the dorsal tubercles of the metatarsal heads before widening and attaching to the bases of the proximal phalanges.
The innervation of the metatarsophalangeal joints is provided by the plantar interdigital nerve, digital branches of the lateral plantar nerve, medial dorsal cutaneous branch of the superficial fibular nerve and the deep fibular nerve.
The flexor digitorum brevis, lumbricals and interossei produce flexion at the lateral four metatarsophalangeal joints. Flexion of the hallux is produced by the action of flexor hallucis longus and brevis.
Extensor digitorum longus and brevis, as well as extensor hallucis longus are all involved in extension at the metatarsophalangeal joints.
Abduction is produced by the adductor hallucis and the plantar interossei, whilst adduction is carried out by the actions of abductor hallucis, the dorsal interossei and abductor digiti minimi.
The trochlear surface of the phalangeal heads articulates with the curved surface of the bases of the corresponding phalanges to form the interphalangeal joints. These hinge joints are stabilised by an articular capsule and two collateral ligaments.
The innervation of the interphalangeal joints is from the plantar interdigital nerves and the medial dorsal cutaneous branch of the superficial fibular nerve. Occasionally, branches of the sural, deep fibular and intermediate dorsal cutaneous nerves innervate these joints.
Flexion is produced by flexor digitorum longus and brevis as well as by flexor hallucis longus in the hallux. Extensor digitorum longus and brevis, as well as extensor hallucis longus are involved in extension of the interphalangeal joints.
Ankle sprains, the most common injury to the ankle joint, result in tears to the supporting ligaments. Inversion injuries are common and usually result in tearing of the lateral ligament, as it is much weaker than the medial ligament. The most vulnerable of the lateral ligaments, the anterior talofibular ligament, is almost always partially or completely torn, resulting in joint instability.
Ankle Joint Fractures
Fractures of the ankle joint are also common and are usually associated with ligamentous injury. Accurate alignment of the joint is important in the treatment of these fractures, as misalignment can result in long-term morbidity.
Congenital Talipes Equinovarus
Congenital talipes equinovarus (commonly referred to as clubfoot) is a congenital condition where the foot is mechanically rotated out of position. It is more common in boys and results in foot inversion, plantar flexion at the ankle joint and adduction at the metatarsophalangeal joints. One or both feet may be affected and treatment involves surgical correction followed by fixation of the joint with a cast. In untreated cases, walking is painful, as they must bear the weight on the lateral surface of the foot rather than on the heel and sole.