Overview
The cat's hind paw normally has four weight-bearing digits, II to V; digit I is absent or reduced to a vestige. Each digit has three phalanges: proximal, middle and distal. The cat stands on the digits through the digital pads, with the proximal phalanges nearly horizontal.
Key features
- Proximal phalanx: the longest; articulates with the head of the metatarsal and with the proximal sesamoid bones.
- Middle phalanx: shorter and asymmetrical; at rest the distal phalanx folds dorsally alongside it.
- Distal phalanx: carries the claw, with the ungual process inside the horny sheath, the ungual crest wrapping the base of the claw and the flexor tubercle for the deep digital flexor tendon.
- Dorsal elastic ligaments: hold the claw retracted at rest; contraction of the deep digital flexor protrudes it. The mechanism is the same as in the forepaw, although the hind claws are used less for gripping and climbing.
Clinical relevance
- Scottish Fold osteochondrodysplasia: short, deformed, irregular phalanges, with exostoses and progressive ankylosis of the distal limb joints.
- Digital fractures and luxations after trauma or entrapment.
- Onychectomy: involves amputation of the distal phalanx; it is performed less often on the hind paw, but the consequences are the same.
- Polydactyly: extra digits, more frequent on the forepaw than on the hind paw.