Anatomy of Metatarsal Bones in Animals: Ox, Horse, Sheep, Goat, Pig, Dog, Rabbit, and Fowl

Metatarsal bones are the long bones located in the hind limb between the tarsal bones and the phalanges (digits). They form the skeleton of the metatarsus, which corresponds to the foot region.

In animals, the number, size, and degree of fusion of these bones vary significantly between species and are adapted according to their mode of locomotion.

Metatarsal Bones of Ox

The metatarsus has two bones in the ox—the large (third and fourth) and the medial small (second) metatarsal bones.

Large Metatarsal Bone (Third and Fourth)

Large metatarsal bone (third and fourth) resembles the large metacarpal except for the following differences:

• The bone is longer than the metacarpal.
• The shaft is four sided.
• The dorsal metatarsal groove is deeper.
• The plantar face presents a shallow groove. Commencing at the upper part of the groove is a vascular tunnel passing obliquely upward and forward through the proximal extremity to open on the articular face of the extremity behind and between the facets.
• The proximal extremity presents a flattened facet laterally for the fused central and fourth tarsal and a large facet on the medial aspect for the fused second and third tarsal, behind which is another small facet for the first tarsal. At its postero-medial aspect, this extremity presents a facet for the small metatarsal bone.
• The dorso-medial aspect presents a tuberosity for the attachment of the tendon of the peroneus tertius.
• The distal extremity resembles that of the large metacarpal.

Medial Small Metatarsal

The medial small metatarsal is a disc-shaped piece of bone situated at the postero-medial aspect of the proximal extremity of the large metatarsal bone.

It presents a small facet on its dorsal face for the large metatarsal. The rest of the bone is rough.

Comparative Anatomy of Metatarsal Bones

The comparative anatomy of metatarsal bones in animals reveals significant variations that reflect each species’ locomotion and weight-bearing adaptations.

Sheep and Goat

Metatarsal bones of sheep and goat resemble those of the ox.

Horse

The horse has three metatarsal bones—one large (third) and two small (second and fourth) medial and lateral metatarsals.

• The large metatarsal resembles the large metacarpal.
• The vertical grooves present in the ox are absent.
• The proximal extremity presents facets for the third tarsal, the fourth tarsal, and sometimes the second tarsal. The shaft is cylindrical.
• The small metatarsals each have two small facets in front for the large metatarsal.
• The lateral (fourth) metatarsal is relatively massive, especially in its upper part.
• The proximal extremity is large and outstanding and bears one facet above for the fourth tarsal.
• The medial bone (second metatarsal) is much more slender than the lateral, especially in its proximal part, which bears two facets above for the first and second tarsal, and sometimes one for the third tarsal.

Pig

• They are four in number in the pig and resemble the metacarpals of the forelimb.
• The second and fifth are placed more towards the plantar aspect of the large bones.

Dog

• Five metatarsal bones are present in the dog.
• The first is small, and the other four are well developed and resemble the metacarpals.

Rabbit

• Metatarsals in the rabbit are four in number.
• They are very narrow, rod-shaped structures.

Fowl

• The tarso-metatarsus is a single bone formed by the fusion of the distal row of the tarsals with the second, third, and fourth metatarsals in fowls.
• The proximal extremity presents two glenoid cavities for the distal end of the tibio-tarsus.
• The shaft is two-sided.
• The first metatarsal is attached by a ligament to the postero-medial border of the large metatarsus. In the male, a conical projection arises from the medial aspect of the body of the metatarsus and serves as a core for the horny spur or calcar.
• The distal extremity divides into three processes.
• Each process is in the form of an articular convexity. The medial one is the shortest and articulates with the second digit.
• The middle one is the longest and articulates with the third digit.
• The lateral one articulates with the fourth digit.