Hemarthrosis - a hemorrhage in a cavity of a joint. Arises at a bruise, more often at intraarticulate damages of a joint (breaks of a capsule, a meniscus, dislocations, subluxations, fractures). Can arise at diseases of a blood with disturbance of system coagulations (hemophilia). The most frequent localization - a knee joint.

Signs, current. The blood fills a cavity of a joint and its torsions, causing a pain, augmentation of volume of a joint, restriction and morbidity of movements.

Complications: transition in chronic current with development of a synovitis; at a becoming infected of a contained joint the purulent arthritis can develop.