Overview of Musculoskeletal System

The musculoskeletal system consists of bones, cartilage, muscles, ligaments, and tendons. Primary functions of the musculoskeletal system include support of the body, provision of motion, and protection of vital organs. The skeletal system serves as the main storage system for calcium and phosphorus and contains critical components of the hematopoietic system. Many other body systems, including the nervous, vascular, and integumentary systems, are interrelated, and disorders of one of these systems may also affect the musculoskeletal system and complicate diagnosis.

Diseases of the musculoskeletal system most often involve motion deficits, functional disorders, and lameness. The degree of impairment depends on the specific problem and its severity. Skeletal and articular disorders are by far the most common and have the greatest economic impact. In horses and dogs, musculoskeletal injuries are a major source of debilitating pain, economic loss, and loss of athleticism. Degenerative joint disease is much more common and has a greater economic importance than acute traumatic injuries or respiratory diseases in performance horses. Several studies estimate that problems involving the fetlock and carpal joints account for 25%–28% of horses lost from training. In addition, tendon injury is a common debilitating injury in performance horses. The healing response is prolonged, and the resultant repair tissue is usually of inferior mechanical strength. Consequently, the prognosis for return to previous levels of performance is poor. In dogs, cranial cruciate ligament injury with resulting osteoarthritis is the most common musculoskeletal injury resulting in lameness. Although perhaps less common, primary muscular diseases, neurologic deficits, toxins, endocrine aberrations, metabolic disorders, infectious diseases, blood and vascular disorders, nutritional imbalances or deficits, and occasionally congenital defects are diagnosed as well.