Pastern

Pastern
The bones and joints of the equine forelimb distal to the wrist (or carpus): The fetlock (metacarpophalangeal joint) is located between the cannon bone (third metacarpal) and the long pastern bone (proximal phalanx). The pastern joint (proximal interphalangeal joint) is located between the long pastern bone and the short pastern bone (middle phalanx). The coffin joint (distal interphalangeal joint) is located between the short pastern bone and the coffin bone (distal phalanx).
Shock absorption of the pastern joint
Details
Latin	Pāstōrius
Anatomical terminology []

The pastern is a part of the leg of a horse between the fetlock and the top of the hoof. It incorporates the long pastern bone (proximal phalanx) and the short pastern bone (middle phalanx), which are held together by two sets of paired ligaments to form the pastern joint (proximal interphalangeal joint). Anatomically homologous to the two largest bones found in the human finger, the pastern was famously mis-defined by Samuel Johnson in his dictionary as "the knee of a horse". When a lady asked Johnson how he came to do so, he gave the much-quoted reply: "Ignorance, madam, pure ignorance."

The pastern consists of two bones, the uppermost called the "large pastern bone" or proximal phalanx, which begins just under the fetlock joint, and the lower called the "small pastern bone" or middle phalanx, located between the large pastern bone and the coffin bone, outwardly located at approximately the coronary band. The joint between these two bones is aptly called the "pastern joint". This joint has limited movement, but does help to disperse the concussive forces of the horse's step and also has some influence on the flexion or extension of the entire leg. The pastern is vital in shock absorption. When the horse's front leg is grounded, the elbow and knee are locked. Therefore, the fetlock and pastern are responsible for all the absorption of concussive forces of a footfall. Together, they effectively distribute it among both the bones of the leg and the tendons and ligaments.

The slope of the shoulder is often the same as the slope of the pastern. The angle of the pastern should also match the angle of the hoof after the latter has been trimmed (the angle will change as the hoof grows and may be off in a few weeks). This keeps the bones of the pastern and coffin joints in proper alignment, with a straight line running through their core. An angle broken forward or back increases the stress on these bones, joints, tendons, and ligaments. If the angle does not match, it could be an indication of poor farrier work, but some horses may have underlying conformational defects that can not be modified through farriery alone.