Primary osteoarthritis of knee

**Definition:** Primary osteoarthritis occurring in an otherwise intact knee joint, involving genetically related, age-related or use-related degeneration with microscopic and macroscopic anatomical changes, which ultimately limit motion in one or more joints. Changes to the joint include increasing cartilage loss and osseous transformation such as sclerosis, osteophyte formation and cysts as well as potential inflammatory changes in surrounding soft tissue structures.