Version July 2025
| Radiograph view | Indications | Comments |
| Anteroposterior (AP) | Standard view Part of trauma series¶ | Soft tissue injury and injury limited to cartilage (chondral fracture) cannot be seen directly on plain radiographs |
| AP weight-bearing | Osteoarthritis (OA) evaluation Assessment of knee alignment | Common to obtain bilateral views for comparison |
| Lateral | Standard view Part of trauma series | Can reveal effusion or lipohemarthrosis commonly seen with fractures Cross-table lateral used if patient cannot bear weight |
| Tangential or axial patella views (eg, Merchant/"skyline" or "sunrise") | Suspected patella injury/fracture, patella subluxation, or patellofemoral joint disease Assessment of trochlea depth | Performed with patient prone Knee flexion of 30° to 45° provides best view of patellofemoral joint Merchant/skyline view obtained with knee flexed approximately 45° Sunrise view obtained with knee flexed approximately 90° or more |
| Rolled lateral | Bedbound patient with suspected OA | Orthogonal view used as alternative to AP |
| Intercondylar ("tunnel") | Suspected intra-articular loose body, tibial plateau or femoral condyle fracture, OA, or osteochondral defect (OCD) | Can be used as alternative to weight bearing plain radiograph for evaluating knee OA |
| Oblique | Suspected fracture of tibial plateau or femoral condyle, or OCD | Often used if computed tomography (CT) scan not available or appropriate |
* General indications for knee radiographs are provided. When the clinical presentation is challenging or referral is likely, it is best to confer with the consulting radiologist or orthopedist about which studies to obtain.
¶ The Ottawa Knee Rule and Pittsburgh Knee Rule can help to determine when plain radiographs should be obtained after acute injury.