Metatarsophalangeal (MTP) joints
The metatarsophalangeal joints (MTP) are synovial joints that connect the metatarsal bones of the foot to the proximal phalanges of the toes. In these joints, the heads of metatarsal bones articulate with the corresponding bases of proximal phalanges.
The metatarsophalangeal joints are condyloid joints that permit flexion, extension, abduction, adduction and circumduction, and play a major role in the stance phase of the gait cycle (walking). The stability of the metatarsophalangeal joints is maintained by its associated capsuloligamentous and musculotendinous structures.
This article will discuss the anatomy and function of the metatarsophalangeal joints.
|Synovial, condyloid, biaxial
|Metatarsal heads, bases of proximal phalanges
|Collateral ligaments, plantar ligaments, deep transverse metatarsal ligaments
|Plantar digital nerves, superficial and deep fibular nerves
|Dorsal metatarsal arteries, plantar metatarsal arteries
|Flexion, extension, abduction, adduction and circumduction
- Articular surfaces
- Joint capsule and ligaments
- Blood supply
- Muscles acting on the metatarsophalangeal joint
- Clinical Relations
The metatarsophalangeal joints are articulations between the rounded heads of metatarsal bones and the shallow concavities found on the bases of proximal phalanges. The articular surface of the metatarsal bone heads covers mainly the distal and plantar surfaces, and are vertically convex. The prominent plantar articular surface allows for plantar flexion at these joints. The head of the first metatarsal bone is also transversely convex, allowing for a wider degree of abduction/adduction relative to the other toes.
The plantar articular surface of the first metatarsal head is unique as it bears two well defined facets which are separated by an anteroposteriorly oriented ridge; a larger medial facet covers approximately two thirds of the palmar articular surface, while a smaller lateral one occupies the remaining one-third. These articulate with the sesamoid bones found within the plantar ligament/plate of the big toe.
Similarly, a sesamoid bone may variably be found at the metatarsophalangeal joints of the second and fifth toes.
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Joint capsule and ligaments
Each metatarsophalangeal joint is enclosed by a loose joint capsule that attaches close to the articular margins and is lined by synovial membrane. This fibrous capsule is supported by collateral ligaments on each side and a plantar ligament on its plantar aspect. The capsule is inseparable from these ligaments. The thin dorsal surface of the capsule is reinforced by fibers from the extensor tendons.
There are three types of ligaments associated with the metatarsophalangeal joint: collateral, plantar and deep transverse metatarsal ligaments.
The collateral ligaments lie on the medial and lateral sides of each metatarsophalangeal joint. These strong ligaments extend in an oblique, or inferodistal, manner from small dorsal tubercles on each side of the metatarsal heads to the corresponding side of the phalangeal bases (phalangeal collateral ligament) and the plantar ligament distally (accessory collateral ligament).
The plantar ligaments (plantar plates) are dense fibrocartilaginous plates that are firmly attached to the plantar surfaces of the phalangeal bases. The dorsal surfaces of the plantar ligaments are slightly concave and form part of the articular surface for the metatarsal heads. The margins of these ligaments blend with the collateral as well as the deep transverse metatarsal ligaments. The plantar aspects of the plantar ligaments bear a groove that accommodates the flexor tendons passing to the toes. The plantar ligament of the first digit is largely replaced by the sesamoid bones and their connecting ligamentous bands which form a canal for the tendon of flexor hallucis longus muscle.
Deep transverse metatarsal ligaments
The deep transverse metatarsal ligaments are four short, wide bands that link the plantar ligaments of adjacent metatarsophalangeal joints together to form a single unit. They prevent splaying (widening) of the forefoot. These ligaments are sandwiched by the interossei tendons dorsally and the tendons of the lumbrical muscles, digital vessels and nerves on the plantar surface.
The plantar digital nerves are the main nerves that supply the metatarsophalangeal joints. The medial plantar nerve supplies the plantar aspects of the first, second, third and medial half of the fourth metatarsophalangeal joint. The lateral half of the fourth joint and the fifth joint are innervated by digital branches of the lateral plantar nerve.
On the dorsal aspect, the metatarsophalangeal joints are mainly supplied by digital branches of the superficial fibular (peroneal) nerve including the medial aspect of the first metatarsophalangeal joint. Only the lateral side of the first metatarsophalangeal joint and the medial side of the second metatarsophalangeal joint receive innervation from the digital branches of the deep fibular nerve.
On the dorsal surface, the metatarsophalangeal joints are supplied by the dorsal metatarsal arteries which are branches of the dorsalis pedis artery.
The arterial blood supply to the plantar aspects of the metatarsophalangeal joints are by the plantar metatarsal arteries which branch off the deep plantar arch.
The deep plantar arch is formed by the lateral plantar artery (from posterior tibial artery) and the deep plantar artery (from dorsalis pedis artery).
The metatarsophalangeal joints permit flexion, extension and limited abduction, adduction and circumduction. Each joint has 2° of freedom.
Flexion (plantarflexion) of the metatarsophalangeal joints causes the toes to be pulled together and to bend towards the plantar aspect of the foot. This movement is performed by flexor tendons that pass to the digits. During active flexion, the first metatarsophalangeal joint allows approximately 45° range of motion whereas that of the lateral four metatarsophalangeal joints permit about 40° of flexion.
Extension (dorsiflexion) of the metatarsophalangeal joints is performed by extensor tendons that pass to the digits. During active extension of the metatarsophalangeal joints, the toes are elevated towards the dorsal surface of the foot and are to a small degree spread out and pointed slightly laterally. The range of extension in the first metatarsophalangeal joint is about 70° whereas that of the lateral four metatarsophalangeal joints permit about 40°. The close packed position of the metatarsophalangeal joints in full extension, while the resting, or open packed position is at 10° of extension. The capsular pattern (or loss of passive range of motion during inflammation) of these joints is variable, however it is generally considered to be extension more limited than flexion, in the case of the metatarsophalangeal joint of the big toe.
Abduction and adduction at the metatarsophalangeal joints are minimal and occur relative to the second digit which serves as the midline.
During passive movement of the metatarsophalangeal joints some accessory movements can be elicited. These include minimal sliding (up and down) and rotation of the bases of the proximal phalanges over the metatarsal heads.
Are you wondering why we don't use 3D anatomy? This article will answer that question and explain much more!
Muscles acting on the metatarsophalangeal joint
All the movements of the metatarsophalangeal joints are performed by the muscles of the leg and foot.
- Flexion of the first digit (great toe) at the MTP joint is primarily by the flexor hallucis longus, the flexor hallucis brevis and the oblique head of the adductor hallucis muscle. Flexion of the lateral four digits is mainly by the flexor digitorum brevis, lumbricals, and both dorsal and plantar interossei. These are assisted by flexor digitorum longus and the quadratus plantae, with the flexor digiti minimi brevis assisting in the fifth digit.
- Extension of the MTP joint of the first digit is carried out by the extensor hallucis longus muscle. Extension of digits 2 to 5 are produced by the extensor digitorum longus and the extensor digitorum brevis muscles.
- Adduction of the MTP of the first digit is by the adductor hallucis muscle, whereas that of the digits 3 to 5 is produced by the corresponding plantar interossei.
- Abduction of the first digit is carried out by the abductor hallucis muscle, while that of the fifth digit is produced by the abductor digiti minimi muscle. Abduction of the MTP of digits 2 to 4 is by the dorsal interossei muscles.
Hallux valgus is a common foot deformity that is associated with the wearing of tight footwear. It is a degenerative disease of the metatarsophalangeal joint of the great toe (hallux). It is characterized by a medial deviation of the first metatarsal and a lateral deviation of the adjoining phalanges of the great toe. This deformity may cause significant pain and impair mobility. The pull of the flexor hallucis longus and extensor hallucis longus muscles may contribute to the progressive worsening of the deformity. As a result of pressure and friction against the footwear, a skin callus and bone spur (exostosis) may develop over the medial aspect of the metatarsal head in addition to a thickened inflamed subcutaneous bursa. These three changes make up a bunion. Depending on the severity, this deformity may be treated with adaptation of footwear and orthotics (splints) or may require surgical management.
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