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→Distal Limb
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=Distal Limb=
=Distal Limb=
==Bones==
====Metacarpals and Metatarsals====
The arrangement of the metatarsals are similar to those of the metacarpals in that they are rod shaped bones, numbered from I to V. The 1st is the most medial and is very small, the 3rd and 4th are the longest. The proximal base of each articulates with it's corresponding carpal bone and the adjacent metacarpal. The distal end is its head, which is transversely cylindrical and articulates with the proximal phalanx. Metacarpals II - V possess a sagittal ridge on their palmar aspects.
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====Phalanges====
The proximal phalanx of the main digits (II - V) have a concave articular surface and the palmar border has a groove to accomodate the articular surface of the metacarpus when the joint is fixed. The distal head has two convex areas separated by a groove. The middle phalanx is roughly two-thirds the length of the proximal phalanx and its base has a sagittal ridge on the articular surface which articulates with the groove of the proximal phalanx. The head resembles that of the proximal phalanx. The distal phalanx is made up of a cone-shaped ungual process with a distinct collar called the 'ungual crest'. The deep ungual groove distal to the crest provides attachment for the proximal border of the claw and articulates with the middle phalanx via a small sagittal crest. A bony sesamoid bone is found on the dorsal aspect of the metacarpophalangeal joint. The 'dew claw' (metacarpal I) is normally present in the forelimb but often not in the hindlimb. It normally only consists of two phalanges that resemble the proximal and distal ones.
==Joints==
====Metacarpophalangeal Joint====
The metacarpophalangeal joint is able to undergo flexion and extension movements. Each joint (except the first digit) has a pair of sesamoid bones associated with the palmar aspect of the joint which articulate with a concave area of the proximal phalanx. The joint capsule runs between the four bones of the joint extending dorsally under the extensor tendon and part also intermingling with an expanding area of the common digital extensor tendon. Distally it binds to the articular cartilage of the proximal phalanx and on the palmar aspect its dorsal attachment is level with the proximal end of the sesamoid bones. The '''collateral ligaments''' bind the the metacarpal bone to the proximal phalanx, with a deep branch attaching to the sesamoid bone. The '''palmar/intersesamoidean ligament''' is a mass of fibrocartilage that embeds the sesamoid bones. The palmar aspect of this ligament forms a groove for the deep flexor tendon to run in. The '''collateral sesamoid ligaments''' connect the outer aspect of the sesamoids to the proximal phalanx whilst the '''distal sesamoid ligaments''', although not well developed in the dog, connect the distal surface of the sesamoids to the palmar aspect of the phalanx. These ligaments include the cruciate and short ligaments. The '''superficial transverse metacarpal ligaments''' surround the flexor tendons and their sheaths at the point of the sesamoid ligaments and the '''distal annular ligaments''' cross the surface of the flexor tendons and sheaths at the level of the proximal and middle phalanx.
====Proximal Interphalangeal Joint====
The proximal interphalangeal joint provides flexion and extension movements. The joint capsule attaches near the articular surfaces of the proximal and middle phalanges and extends slightly in a pouch dorsally and more extensively on the palmar aspect. The dorsal capsule is reinforced by a fibrocartilaginous nodule; the extensor tendon attaches to the capsule here. The '''collateral ligaments''' connect the distal end of the proximal phalanx to the proximal end of the middle phalanx and lie in a vertical direction rather than along the bone axis.
====Distal Interphalangeal Joint====
The distal interphalangeal joint allows extension and slight flexion movements. The joint capsule attaches to the articular periphery of the bones and has a small fibrocartilagenous bead in the palmar aspect. The '''collateral ligaments''' connect the distal part of the middle phalanx to the sides of the ungual crest of the distal phalanx. The '''dorsal ligament''' connects the proximal dorsal border of the extensor process of the distal phalanx. These are paired in dogs and function is to keep the claw raised until contraction of the deep digital flexor acts to overcome their tension.