Perform a lateral knee with the patient’s knee flexed 20–30°. Direct the central ray about 1 cm distal to the medial femoral epicondyle, angling approximately 5–7.5° cephalad. This slight cephalic tilt helps superimpose the femoral condyles and open the joint space for optimal visualization of the patellofemoral and tibiofemoral compartments for assessment of fractures and joint alignment.

Normal knee flexion is roughly 0–135°. For examining the lateral meniscus (McMurray test) clinicians typically flex the knee to about 90°. After lateral meniscal repair or some lateral knee procedures, protocols often limit flexion to 0–90° for the first 4–6 weeks, then gradually progress to full flexion as healing, pain, and surgeon guidance allow.

Knee flexion at 160 degrees means the knee is bent so the lower leg forms a 160° angle with the thigh — a very deep bend beyond the usual clinical range (~0–135°). This degree of flexion reflects high mobility or hyperflexibility seen in deep squats or some activities. If achieved without pain or instability it can be normal; if painful or forced, seek medical assessment.

A normal knee X‑ray shows proper alignment of the femur, tibia and patella with preserved, even joint spaces indicating healthy cartilage (cartilage itself isn’t seen). Bone cortices are smooth and continuous without fractures, lytic lesions, osteophytes or abnormal bone density. No significant soft‑tissue swelling or joint effusion is evident. Overall, joint surfaces appear congruent and symmetrical.

Knee flexion angle is the angle between the thigh (femur) and lower leg (tibia) when the knee bends. Measured with a goniometer, 0° denotes full extension and normal maximum flexion is about 130–140°. Typical functional requirements: walking ~60°, stair climbing ~80–90°. It helps assess injury, arthritis, surgical outcomes and guide rehabilitation progress.

Normally the lateral patellofemoral angle opens laterally and measures approximately 8–15° (many references use >8° as normal). It’s measured on axial (skyline/Merchant) knee radiographs by comparing the lateral patellar facet to the anterior femoral condyles. A reduced, zero, or negative angle indicates abnormal patellar tilt/instability and may prompt further clinical or imaging assessment.