Locking Stifle: What is it, and what can we do about it?

Does your horse drag the hind legs, appear stiff in the back end, struggle to rein-back, protest when you ask them to collect? They could be suffering from locking stifle.

Locking stifle is when the stifle (equivalent to the human knee joint) gets stuck in an upward position. It can be caused or caused by poor conformation, weak muscles or incorrect training. Old age and arthritis can exacerbate the problem. When the stifle joint is locked, it becomes temporarily unable to bend, sometimes enough that the horse is temporarily unable to move. However, locking stifle can also be less obvious than this: if the stifle has locked in the past, sometimes, a horse becomes reluctant to utilitse the full range of movement of the stifle joint in case it locks again. They will make smaller movements and sometimes appear stiff in the back legs as a result. Some horses will drag the hind legs.

Horses with locking stifles tend to really struggle with exercises like rein-back and lateral exercises, and can begin to show signs of discomfort, such as headshaking, rubbing the head or nipping, when they are asked to collect.

This is because the stifle joints work together with the hocks. In order to collect, rein-back or carry out lateral work, the hock and stifle joint need to bend more and carry more weight.

In order to help the horse to overcome this issue, strength needs to be built in the muscles around the stifle joint, but this work needs to be approached with great sensitivity, because we need to be careful not to ask too much too soon which can cause the stifle to lock again.

Slow walk work is absolutely ideal for this because it enables us to build strength and confidence gently and gradually without risking damage or pain. When I’m using slow walk work to rehabilitate horses with locking stifles, I work mostly on transitions between walk and halt, collect and stretch, with a focus on coming to the edge of the horse’s ability to bend the joints, without overstepping beyond what they can manage. Rein-back and lateral work must only be introduced with the utmost of caution: I tend to keep these exercises to a minimum, only introducing them when the horse is ready, or sometimes not at all.