In a horse possessing ideal conformation, when viewed from the side you should be able to envision a straight line from the forearm, through the knee, cannon bone and down to the back of the heel. As the front legs support 60-65% of the horse’s weight, they tend to suffer from more wear-and-tear than the hind legs. Correct, straight forelimbs are better-equipped to avoid the injuries suffered by misaligned legs. This includes those that are over at the knee, back at the knee (calf-kneed), or tied-in under the knee.
Over at the knee (sprung knees)
The knee looks like it is buckling forward, which can apply greater strain to tendons and suspensory ligaments. It is sometimes caused by an injury to the check ligament or the structures at the back of the knee. The extra stress applied to the tendons increases the risk of bowed tendons, as well as injury to the suspensory ligament and sesamoid bones.
Back at the knee (calf-kneed)
The line of the knee and cannon appears to be curving backward. This places excess stress on the knee joint as it overextends, which is especially detrimental to horses in speed sports. It also produces strain on the tendons, bones and ligaments, causing knee chips and bowed tendons, as well as compression fractures to the front of the carpals and/or knee ligament injury. Proper shoeing that eliminates long-toe, low-heel can help.
Tied-in at the knee
Ideally, the cannon should appear the same width along its length. In a tied-in leg, the tendon appears narrower where it meets the back of the knee. This limits the strength of the flexor tendons that absorb impact concussion through the legs and can make the horse prone to tendon and joint injuries, especially in high-impact events such as jumping, eventing, racing, and endurance.
