Systemic onset JIA may cause inflammation of the internal organs as well as the joints, though joint swelling may not appear until months or even years after the fevers began
[rheumatology.org]
It causes joint swelling, pain, stiffness, and loss of motion. It can affect any joint, but is more common in the knees, hands, and feet.
[icdlist.com]
It can include redness, joint swelling and pain, often in knees, ankles, and feet.
[webmd.com]