|Small marginal osteophytes (arrows) of the processus anconeus of the ulna can be seen in this gross pathological specimen of a sow.|
Osteophytes are exostoses (bony projections) that form along joint margins. They should not be confused with enthesophytes, which are bony projections that form at the attachment of a tendon or ligament. Osteophytes are not always distinguished from exostoses in any definite way, although in many cases there are a number of differences. Osteophytes are typically intra-articular (within the joint capsule).
A range of bone-formation processes are associated with aging, degeneration, mechanical instability, and disease (such as diffuse idiopathic skeletal hyperostosis). Osteophyte formation has classically been related to sequential and consequential changes in such processes. Often osteophytes form in osteoarthritic joints as a result of damage and wear from inflammation. Calcification and new bone formation can also occur in response to mechanical damage in joints.
Osteophytes form naturally on the back of the spine as a person ages and are a clinical sign of degeneration in the spine. In this case, the osteophytes are commonly not the source of back pains, but instead are a sign of an underlying problem. However, osteophytes on the spine can impinge on nerves that leave the spine for other parts of the body. This impingement can cause pain in both upper and lower limbs and a numbness or tingling sensations in the hands and feet because the nerves are supplying sensation to their dermatomes. 
Normally, asymptomatic cases are not treated. Non-steroidal anti inflammatory drugs and surgery are two typical options for cases requiring treatment.
- "osteophyte" at Dorland's Medical Dictionary
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- Bone spurs MayoClinic.com
- Mayo Clinic website concise information on bone spurs