Similar to the human knee, the horse’s knee joint is like a hinge – the largest hinge in the equine skeletal system. Sometimes the knee joint locks up due to overwork or hereditary joint problems. When this happens, its hind legs appear to be stuck in an extended state, often setting off alarms. But don’t stress it — a locked back knee is relatively common. While mild cases may appear vague (only mild lameness), there are ways to get your horse to vocalize again, usually without invasive surgery. However, if left untreated, horses exhibiting routine locking knees may not be safe and may require surgery.
What is a locked knee?
The knee joints help the horse flex its hind legs and stabilize itself because these joints are actually designed to lock when standing. This important function is part of a horse’s bracing apparatus (the arrangement of hindlimb muscles, tendons, and ligaments that work together so it can stay standing with very little muscle power).This action comes into play during sleep, keeping the horse upright. A locked knee occurs when one of the ligaments remains hooked on the ridge of the femoral head. Usually, the horse can easily bend the joint to unlock it. However, in some horses, unlocking is delayed. Small delays can cause mild symptoms, but longer delays can lead to more severe symptoms. Medically, this condition is known as “patella-up fixation.”
Symptoms of Knee Lockout in Horses
Horses with locked hind legs may exhibit a slight lameness in the hindquarters, which can easily go unnoticed. Simple hesitation can result as the horse responds to discomfort and stiffness, especially after prolonged immobility.This horse can trip or knuckle on the rear end, especially on downward transitions, such as trail rides with downhills. A locked knee may also result in a short stride and show difficulty changing the lead when jogging. Alternatively, a horse might try to jog on different leads back and forth, or jump slightly, swinging its hind legs. If you notice a problem with your horse working in circles or dragging its toes, don’t think of it as bad behavior or a bad habit. Consult your veterinarian to diagnose the problem so you can begin treatment.
In severe cases, the horse’s hind legs can appear so pronounced that it is difficult to ignore. When it tries to walk, it may extend its leg, or it may kick back and take a strange step to release the knee joint. Your horse may not be able to relieve its locked joints on its own and may drag its legs behind. Then, for no apparent reason, the leg may snap back to its normal position (you may even hear a click when this happens). If this happens – even if everything looks fine – have it checked by a professional.
Causes of Locked Knee
A locked knee is most commonly seen in ill-fitting ponies, foals, and horses, but the exact cause is unknown. There has been speculation that this may occur in young horses when bone grows faster than muscle because of its rapid growth rate.Even a small growth spurt can change the angle of a horse’s joint, causing it to function improperly. Another theory is that an unhealthy horse (or a horse that suddenly loses muscle tone) may develop the condition for a similar reason – the joint angle is suddenly damaged and therefore locked.
Diagnosing a Locked Knee
In severe cases, a locked back knee joint will be very noticeable. The horse will have difficulty moving its legs normally. However, don’t mistake a locked hind leg for a rope, it is a neurological disorder that can cause excessive and uncontrollable movement, sometimes causing your horse to jerk the hind leg high up in the stride.In any case, a veterinarian will need to examine your horse and manipulate its knee joints to see if she can manually induce the unlocking mechanism. Afterwards, X-rays may be done to see if the lameness is due to other causes, such as bone abnormalities. Finally, your veterinarian may perform a local nerve block to determine if the lameness is really caused by pain, or if it’s really a mechanical problem.
For mildly locked knee cases, exercise and balanced hoof trimming may help your horse. Lack of fitness can lead to weak muscles and ligaments, so simply conditioning your horse can sometimes help with choking.For severe lockout, have your farrier “shake” or roll the hooves. Or have him outfit your horse with orthopedic shoes and pads to help the hooves break through before lock-in occurs.
Certain cases that do not respond to conditioning or corrective farrier work may require a procedure called a medial patella detomectomy by a veterinarian.During the procedure, the veterinarian will make a small incision in the patellar tendon while the horse is sedated and standing. This releases tension in the ligaments, allowing enough movement in the joint (and relieves jamming). However, since releasing the ligaments often results in instability of the patella itself, the disadvantage of this surgical treatment is the potential for development of arthritis and bone spurs.
How to Prevent Locking of the Knee
Since the lack of muscle tone can cause the knee to lock, the horse should be exercised gradually. Activities like trail running, while increasing distance and speed very slowly over several weeks, will help the horse reach its fitness level in a safe manner. Also, try cavaletti training on log jumps or pole work to get your horse on its feet. Sprinting your horse in a line or riding on a slight incline so that it drives with its hindquarters is also safe for training when done at smaller, slightly increased intervals. It is important to start slowly, avoid overworking your horse, and thoroughly discuss your strategy with your veterinarian before starting any training regimen.
If you suspect your pet is sick, call your veterinarian right away. For health-related questions, be sure to consult your veterinarian, as they have examined your pet, know your pet’s health history, and can give your pet the best advice.