Does hip joint effusion refer to synovitis?

Hip joint effusion does not necessarily indicate synovitis. Synovitis commonly leads to increased hip joint effusion and is the most frequent cause of such effusion. When the synovial membrane is weakened, even an aseptic inflammatory process can cause varying degrees of irritation to the synovium, disrupting the balance between synovial fluid secretion and absorption—thereby increasing intra-articular fluid accumulation. This excess fluid may subsequently result in pain and swelling. Other potential causes of hip joint effusion include avascular necrosis of the femoral head, osteophyte formation (bone spurs), and tuberculous hip arthritis.