Degenerative suspensory ligament desmitis (DSLD) is a chronic, debilitating disease occurring primarily in Peruvian Pasos and Peruvian Paso crosses. However, many other breeds are afflicted as well. DSLD is characterized by a slowly progressing bilateral or quadrilateral lameness. Typically, the owner does not recall any trauma or performance related injury. Fetlock effusion, static and dynamic hyperextension and degenerative joint disease are hallmarks on physical examination. Ultrasonography of affected ligaments reveals diffuse loss of echogenicity, and an irregular fiber pattern. Though until recently DSLD was considered a collagen disorder strictly limited to suspensory ligaments (SLs), our data show that it is a systemic disease involving tissues with high content of collagen.  We have identified abnormal accumulations of proteoglycans not only in the SLs, but also in the superficial and deep digital flexor tendons, patellar and nuchal ligaments, aorta, coronary arteries and sclerae of DSLD-affected horses.  Our most recent data point to the presence of an abnormal form of decorin in these proteoglycan deposits. This decorin also exhibited altered biological activity.  Treatment for DSLD-affected horses is empirical and directed at minimizing musculoskeletal pain and providing support for the suspensory apparatus.  Restricted exercise, supportive bandages and nonsteroidal anti-inflammatory drugs provide some, but usually only temporary relief.  Unfortunately, unrelenting pain, severe lameness and suffering require all too often humane euthanasia.

Key words: Decorin; Degenerative suspensory; Horses (Peruvian Pasos and crosses); Lameness; Ligament desmitis; Pathology; Proteoglycans; Treatment