Definitions of the severity of patellofemoral and tibiofemoral ROA
| Normal x-rays | Mild ROA | Moderate/severe ROA | |
|---|---|---|---|
| Patellofemoral joint | Skyline K–L = 0 or 1 and Lateral osteophytes = 0 | Skyline K–L = 2 or Lateral osteophytes = 1 or 2 | Skyline K–L ≥3 or Lateral osteophytes = 3 |
| Tibiofemoral joint | PA K–L = 0 or 1 and Posterior osteophytes = 0 | PA K–L = 2 or Posterior osteophytes = 1 or 2 | PA K–L ≥3 or Posterior osteophytes = 3 |
K–L, Kellgren and Lawrence score; PA, posteroanterior; ROA, radiographic osteoarthritis.