How the Horse's Knee Works - The Key to Movement and Performance (Part I)

The horse has a unique knee structure that provides advantages but can also be a source of health problems, limiting performance, and its use in sports and work. Due to its ability to hook the patella (kneecap) to the side, the horse can relax and sleep standing. However, this mechanism, if not functioning correctly, can cause many movement-related issues.

A crucial fact to mention right from the start is that the knee and hock function as a unit. This means that the movement of one cannot be separated from the other. Simply put, when the horse bends its leg at the knee, the same degree of bending occurs in the hock.

One common reason for this is arthritis in the knee or hock. This can be a significant problem when jumping the horse over an obstacle, especially when it bends the hind limb over the jump but cannot bend the knee or hock into a folded position, causing the leg to hang down. The horse may then hit the jump with its hind leg. When selecting a show-jumping horse, it’s essential to evaluate whether its anatomy or health issues will allow the knee to fold into the proper position.

As an example, I have included the following photos showing in practice how the lack of sufficient limb bending affects the performance of a show-jumping horse and can even lead to a fall during the jump. Moreover, the rider will face many riding challenges, as the horse will tend to favor one hind leg, resulting in lameness and associated riding difficulties.

Fig. 2: Notice the uneven bending of the hind limbs at the hock and knee and the hanging hoof.

Fig. 3: The hanging of the right hind leg is a frequent cause of hitting the pole, due to insufficient folding of the leg into a "harmonica" shape.

Fig. 4: Since the horse consistently fails to fold the right hind leg like the left and lets it hang down, it often causes the jump to be knocked down. This frequent occurrence leads to misunderstandings during training. Many riders even punish horses for knocking down obstacles or use improper training methods because they are unaware of the horse's real issue and don’t know how to address it in training.

Fig. 5: This photo clearly shows the difference in the bending of the hind limbs.

Fig. 6: Here, upon landing, we see the typical movement of the hind limb to the side when the horse refuses to load the leg after landing.

Fig. 7: This is what it looks like when the horse refuses to load the hind leg with its weight after landing. It’s still the right hind limb.

As shown throughout the course of the jump, this is not an accidental problem; the horse consistently has trouble folding the right hind leg into a "harmonica" shape during the jump.

In the following image, the horse symmetrically folds both hind limbs underneath its body during the jump and has no problem with take-off or landing on either leg.

Fig. 8: Symmetrical bending of both hind limbs.

It’s not only important for show-jumping horses that the knee functions properly, but the proper function is crucial for any horse. If the knee doesn’t perform as it should, it leads to movement disorders of the limb, and one of the symptoms of knee or hock problems is dragging the toes of the hind hooves.

Fig. 9: Dragging of the hind hoof toes.

From the perspective of determining the cause of reduced knee functionality, this is very difficult in practice. This means that if the horse has an improperly functioning hock, it will negatively impact knee movement, leading to knee damage, and vice versa. A knee issue can secondary cause a problem in the hock.

Because of the interconnectedness of the knee and hock during flexion, bending tests to detect arthritis and other causes of lameness are not effective. X-rays or ultrasound can be used to detect movement disorders, but often the cause cannot be identified even with equipment. In many cases, the issue lies in the anatomical predisposition of the leg structure, which causes limitations in knee bending or hock instability.

Especially in certain breeds and horses with specific body structures, there is a significant predisposition for the horse to suffer from chronic difficulties and restricted movement and load on the hind limbs.

In the next part, we will discuss more about the structure of the knee and why the problems described above occur.