The proximal interphalangeal joints of hand are the joints between the proximal and middle phalanges.
It is called pastern joint in ungulates.
In carnivores, the first digit does not have a proximal interphalangeal joint. The joint capsules are similar to the ones of metacarpophalangeals with dorsal and palmar recess (pouches) and acartilagenous enforcement dorsally. The medial and lateral collateral ligaments are the only ligaments bridging the joint vertically on the lateral and medial aspects.