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The deterioration that occurs within the knee joints of patients with rheumatoid arthritis appears to be coordinated locally. An analysis of the cell types and enzyme content was performed on various sections of 150 rheumatoid arthritic knee joint samples. Cell type patterns were irregular in patients with advanced disease indicating pockets of deteriorated tissue. The cells seen most frequently at sites of deterioration included those involved in the inflammation process such as fibroblasts, polymorphonuclear leukocytes, mast cells, and macrophages. Few samples showed evidence of enzyme production.

Four weeks after Bo Jackson, star running back for the Los Angeles Raiders and professional baseball player, partially dislocated his hip, tests revealed that avascular necrosis (in which bone cells die because of lack of blood supply) and chondrolysis (cartilage degeneration) had started. These are not uncommon consequences of hip dislocation, but partial hip dislocation is an unusual injury for a football player. In any event, such complications must be recognized early, if permanent damage is to be avoided. One sign of early avascular necrosis is persistent pain when the patient puts weight on the hip, but when patients avoid weight-bearing, as Jackson did, pain may not develop. Follow-up with bone or magnetic resonance imaging (MRI) scans, which show bone and soft tissues in great detail, is recommended four weeks after a hip dislocation. Avascular necrosis is associated with the use of glucocorticoids and alcohol; scuba divers and people with sickle cell anemia are also vulnerable to this complication. Chondrolysis usually develops only after the bone tissue dies. The rate of disappearance of cartilage from the hip joint was particularly rapid in Jackson's case. His physicians recommended that he not play baseball in the 1991 season, and Jackson was released by the Kansas City Royals on March 18. Although signed by the Chicago White Sox within a few weeks, whether he will return to professional sports is not known. Cartilage does not grow back, and hip replacements are performed to relieve pain, not to restore motion. People cannot compete in contact sports after such procedures. Bo Jackson's unfortunate injury is a reminder that injuries not commonly associated with sports can happen to anyone - even to star athletes. (Consumer Summary produced by Reliance Medical Information, Inc.)