"Bone spur" is a term used to describe a sharp bony projection that is usually visible along the margin of an affected joint. Spurs are typically detected during radiographic or ultrasonographic examination of horses, although can also be evident on CAT scan and MRI images.
There are two primary types of spurs:
OSTEOPHYTES: This type of spur occurs at the junction of articular cartilage and underlying bone along the margin of the joint. Osteoarthritis (OA) is a term used for describing a series of changes that occur to joints and their cartilage surfaces leading to what we know as arthritis (joint pain). As some diseased joints become unstable, the body attempts to improve stability via the formation of extra bone around the margins of the joint(s). In some cases, this extra bone may manifest as a bone spur.
ENTHESIOPHYTES: Spurs can also form along the bony attachment of the joint capsule or ligaments around the joint. These spurs are called enthesiophytes. Unlike osteophytes which represent joint instability, enthesiophytes occur at the insertion of joint capsules, tendons, and ligaments and represent the radiographic changes associated with tearing of the fibers that attach these structures to the bone.
It is important to realize that a bone spur is a radiographic abnormality that may or may not be represent inflammation or pain (arthritis) associated with the joint. In other words, many bone spurs have no clinical significance and are not associated with lameness.
It is also important to realize that those spurs considered to be clinically-significant are not a CAUSE of joint inflammation but rather a CONSEQUENCE of joint disease. Therapy, therefore, is directed at managing the primary problem (such as arthritis) rather than specifically addressing the presence of the spur.
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