It is the most common (occurring in 75 per cent cases of ARF) manifestation of ARF. It involves large joints, it is typically fleeting in character shifting from one large joint to another. Knees, ankles, elbows and wrists are the common joints involved. There is synovitis and synovial fluid shows polymorph cells. Joint swelling and pain usually resolves in 4-6 weeks and there is no residual deformity of joints.