HOW HORSES COPE WITH FORELIMB PAIN BY ANN RAMSEY, CERA Apf
Forelimb lameness is common enough that most horse owners can recognize the signs and symptoms. What often goes unnoticed is the compensation occurring in the neck muscles of the horse. Neck muscle bracing is how horses change the loading over the front end to mitigate pain sensations coming from the forelegs. During this time the neck muscles can become overtaxed, painful and stiff. This neck muscle pain must be addressed at the same time as the forelimb lameness, and perhaps for a long time after it’s been resolved.
HOW DOES BRACING THE NECK HELP THE HORSE?
Most horses will have a forelimb lameness at some point in their life. Horses who are lame in either front leg develop the classic “head bob” in conjunction. This distinctive gait feature with the head and neck swinging upward while the painful leg is on the ground, is relieving the horse’s discomfort. The equine head and neck weigh a few hundred pounds and swinging these structures up as the painful leg lands, reduces the load on that limb.
This compensation brings the horse some immediate relief. It’s a strategy that works well so long as the lameness is short lived, as with a hoof abscess or stone bruise. However, horses diagnosed with chronic conditions such as navicular disease, ringbone, or arthritis of the forelegs will end up over using their neck muscles to subtly reduce the pressure placed over the forelimbs. This is particularly common in bilateral lameness cases, (where both front legs are affected). Horses with bilateral forelimb pain can mask the lameness well because both sides of the neck will brace to create equal stride length of the forelimbs.
Many horses can “disguise” an underlying lameness this way for years until finally the pathology in the feet or legs becomes too much. Some horses will have acutely painful necks and may develop neck arthritis in extreme cases. Because the compensation of the neck is a protective response, it can become a more permanent movement pattern. Therefore, neck muscle bracing can continue after the horse is no longer acutely lame, causing pain and performance problems.
QUICK ANATOMY LESSON
According to authors of Activate Your Horse’s Core, Hillary Clayton and Narelle Stubbs, the equine neck is a complex structure and it houses the most mobile vertebrae in the spinal column. Despite being highly mobile, the neck can be a stabilizing structure as it has robust muscle attachments to the body trunk and forelimbs. There are many complex muscle groups and structures in the horses’ neck. Many of these muscle groups contribute to help the horse, but let’s look at just two muscles that are frequently sore and over used in the lame horse.
The muscle called brachiocephalicus runs from the base of the horse’s skull at the occipital bone, and attaches to the humerus; a large bone in the forearm just below the shoulder. The muscle called omotransversarius runs from the wing of the first neck vertebrae called the atlas, to the spine and body of the scapula. The function of these muscles under normal movement is to advance the limb forward by extending the shoulder.
In a painful forelimb, brachiocephalicus and omotransversarius can be used to brace the base of the neck and by pulling the forelimb upward, thus limiting the full range of motion of the limb. This can help the horse continue to move forward while reducing his pain and pressure through the forelimbs.
