ABSTRACT
Disorders of the locomotor system are of enormous social and economic significance in terms of their morbidity. Metabolic bone diseases are a group of generalized skeletal disorders that result from abnormal formation, resorption, or mineralization of bone. Paget's disease is a disorder of excessive turnover of bone that results in the disorganization of bone architecture. Paget's disease starts at one site in a bone and gradually extends with a lytic advancing front. Osteopetrosis is a bone disease characterized by increased bone density due to defective osteoclastic activity. Many systemic diseases, e.g. chronic heart, respiratory, liver, and renal disease, cause muscle weakness. Unlike myasthenia gravis, in the Eaton–lambert syndrome muscle weakness improves with repeated exercise. An antibody to presynaptic structures prevents release of acetylcholine at the nerve terminal. Locomotor diseases, principally osteoporosis and arthritis, are a major source of morbidity, especially in middle-aged and elderly individuals, and therefore have an economic cost for society.
