Bony structures and general topography
On the oblique-horizontal section of the foot (according to Spalteholz), the main bony structures forming the joints of the lower extremities are visualized. This complex includes the tibia (tibia) and fibula (fibula), which form the tibiofibular syndesmosis and the ankle joint.
The tarsal bones are located below:
- Talus (talus) — a connecting link participating in both the ankle and subtalar joints.
- Calcaneus (calcaneus).
- Navicular (os naviculare) and cuboid (os cuboideum) bones.
- Cuneiform bones (medial and lateral).
Subtalar joint
The subtalar joint (art. subtalaris) is formed between the posterior articular surfaces of the calcaneus and the talus. In configuration, these surfaces represent small segments of a cylinder. The joint has a completely enclosed joint capsule and is additionally fixed by auxiliary ligaments located along the lateral surfaces. The section also reveals the strong interosseous talocalcaneal ligament (lig. talocalcaneum interosseum), which reinforces the talocalcaneal connection.
Transverse tarsal joint (Chopart's joint)
Chopart's joint (art. tarsi transversa) is a complex articulation uniting the anatomically isolated calcaneocuboid (art. calcaneocuboidea) and talonavicular (art. talonavicularis) joints. The joint cleft has a characteristic shape resembling a transversely oriented letter S.
The projection of the joint line onto the skin is determined 2.5–3.0 cm distal to the medial malleolus and 4.0–4.5 cm distal to the lateral malleolus.
The most crucial structure here is the bifurcated ligament (lig. bifurcatum). It originates from the upper margin of the calcaneus and divides into two bundles: one going to the posterolateral edge of the navicular bone and the other to the dorsal surface of the cuboid bone. This short and massive ligament is known as the "key" of Chopart's joint. In operative surgery, transecting this specific ligament is a mandatory requirement for wide separation of the bones during disarticulation of the foot.
Tarsometatarsal joints (Lisfranc's joint)
The Lisfranc joint complex (articulationes tarsometatarsales) connects the tarsal and metatarsal bones. The 1st, 2nd, and 3rd metatarsal bones articulate with the three cuneiform bones, while the 4th and 5th metatarsal bones form a joint with the cuboid bone.
Structural features:
- The joint line forms an arch with a prominent rectangular projection directed posteriorly (in the region of the base of the 2nd metatarsal bone).
- The projection of the joint cleft runs from a point posterior to the tuberosity of the 5th metatarsal bone to a landmark 2.0–2.5 cm distal to the navicular tuberosity.
- The joint capsules of the first three joints are completely isolated from one another, whereas the 4th and 5th metatarsal joints are enclosed in a common joint capsule.
Metatarsophalangeal joints
These articulations provide mobility to the toes. Their joint cleft is projected on the dorsum of the foot 2.0–2.5 cm proximal to the plantar digital fold.
On the dorsal surface, they are covered by the extensor tendons. On the plantar side, the joints are protected by the transverse head of the adductor hallucis muscle (caput transversum m. adductoris hallucis) and the osteofibrous flexor canals. The first joint is additionally stabilized from the medial side by the tendon of the abductor hallucis muscle (m. abductor hallucis).
Movements in these joints are limited: slight abduction and adduction are possible, as well as general flexion of the toes. A distinguishing feature of their biomechanics is that the range of dorsiflexion significantly exceeds that of plantarflexion, which is the opposite of the kinematics of hand joints.
Briefly: answers to topical questions
What anatomical structure serves as the "key" of Lisfranc's joint?
The "key" of Lisfranc's joint is the medial interosseous cuneometatarsal ligament (lig. cuneometatarsalia interossea mediale). This anatomical structure runs from the medial cuneiform bone to the base of the 2nd metatarsal bone. Only after the transection of this ligament does the joint open widely, which is a necessary condition during foot disarticulation. Additionally, the joint is reinforced by dorsal and plantar ligaments.
Which ligaments reinforce the subtalar joint?
The subtalar joint is reinforced by the interosseous talocalcaneal ligament, as well as auxiliary collateral ligaments.
- Interosseous talocalcaneal ligament (lig. talocalcaneum interosseum) is the main structure reinforcing this articulation.
- Auxiliary ligaments reinforce the joint capsule laterally.
The capsule of the joint itself is a completely enclosed joint cavity, and its shape is formed by segments of a cylindrical surface.
Which muscles and tendons lie adjacent to the first metatarsophalangeal joint and stabilize it?
The first metatarsophalangeal joint is adjacent to and stabilized by flexor and extensor tendons, as well as the muscles of the great toe.
- Toe extensor tendons cover the joint dorsally.
- Toe flexor tendons cover the joint plantarly, passing through osteofibrous canals.
- Transverse head of the adductor hallucis muscle (caput transversum m. adductoris hallucis) lies adjacent to the plantar side.
- Abductor hallucis muscle (m. abductor hallucis): its tendon additionally reinforces the joint from the medial side.
The composition of Chopart's joint can be memorized using the "cross" rule: the talus (medial) articulates with the navicular (medial), while the calcaneus (lateral) articulates with the cuboid (lateral). The "key" to this joint is the bifurcated ligament, which acts like a key unlocking the two joint "doors" during surgery.
Class and exam questions
Which joints form the transverse tarsal joint?
Chopart's joint (transverse tarsal joint) comprises two separate articulations: the calcaneocuboid and talonavicular joints.
What is the clinical significance of the bifurcated ligament?
The bifurcated ligament (lig. bifurcatum) is the "key" of Chopart's joint. Only its complete transection allows surgeons to widely separate the articular surfaces for successful foot disarticulation.
What are the features of the joint capsules in Lisfranc's joint?
The articulations of the 1st, 2nd, and 3rd metatarsal bones have three separate, completely isolated joint capsules, whereas the joints of the 4th and 5th metatarsal bones share a single common capsule.
What is the main difference between the movements of the toes and the fingers?
In the metatarsophalangeal joints of the foot, the range of dorsiflexion of the toes significantly exceeds the range of plantarflexion, whereas the opposite is true for the hand.
What else to study on this topic
- Anatomy of the ankle joint (art. talocruralis) and its ligamentous apparatus
- Structure of the tibiofibular syndesmosis (syndesmosis tibiofibularis)
- Cuneonavicular joint (art. cuneonavicularis)
- Topography of osteofibrous canals and flexor tendons on the sole
- Talocalcaneonavicular joint (art. talocalcaneonavicularis) on an oblique-horizontal section
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