text: <unk>  is characterized by acute or chronic inflammation of a bursa and buildup of fluid in the bursal sac. A bursa is a small, fluid-filled sac that acts as a cushion between a bone and other moving parts: muscles, tendons, or skin. Over 160 bursae are found throughout the body, though relatively few of them can cause<unk> .
  Aseptic<unk>  can be caused by overuse and repetitive injuries to the joint, abnormal bony structure, and crystal deposit in the bursa. It commonly affects the knee or the elbow as a result of kneeling or leaning on the elbows for a longer period of time than usual. Moreover, septic<unk>  can be caused by bacterial infection of the bursa through skin injury following repetitive trauma.
option_0: Bursitis pathophysiology
option_1: Septic arthritis pathophysiology
option_2: Ankylosing spondylitis pathophysiology
option_3: Osteomyelitis pathophysiology
option_4: Osteoarthritis pathophysiology
option_5: Back pain pathophysiology
option_6: Osteoarthritis causes
option_7: Rheumatoid arthritis pathophysiology