Foot Arthritis Niece (26 Years Old) Has Swollen Leg And Foot. Arthritis Says Doctor???

Niece (26 years old) has swollen leg and foot. Arthritis says doctor??? - foot arthritis

Has anyone heard of it. One of his legs and feet (the same leg is swollen). She had an MRI. The doctor said it was a type of arthritis. I find no name for this state on this issue - Arthritis was too broad a statement. The grandmother could not remember what the doctor said it was called. Help please.