How is fluid accumulation in the knee formed?

Knee effusion, also known as synovitis or fluid accumulation in the knee joint, is primarily caused by irritation or inflammatory reactions of the synovial membrane within the knee. Under normal circumstances, a small amount of synovial fluid exists inside the knee joint. This synovial fluid, secreted by the synovial membrane, serves to lubricate and nourish the articular cartilage. However, when inflammation occurs in the synovial membrane, excessive synovial fluid is secreted, leading to an increased volume of fluid within the joint cavity and resulting in knee effusion.

Causes of knee effusion:

1. Trauma: Injuries such as knee sprains, ligament damage, or fractures can easily injure the synovial membrane, triggering an inflammatory response and subsequent fluid accumulation.

2. Infection: Bacterial, viral, or fungal infections can cause inflammation of the synovial membrane within the knee joint, leading to fluid accumulation.

3. Rheumatic diseases: Conditions such as rheumatoid arthritis, gout, and ankylosing spondylitis can cause the joint synovium to remain in a state of chronic inflammation, resulting in persistent effusion.

4. Overuse: Frequent running or jumping can cause excessive wear and tear on the synovial membrane, triggering inflammation and fluid accumulation.

5. Degenerative changes: With aging, the cartilage in the knee joint wears down, which may cause inflammation of the synovial membrane and subsequent fluid accumulation.