A knee lateral view X‑ray is a side‑view radiograph taken with the affected knee slightly flexed (about 20–30°). It shows the femur, tibia, patella and joint spaces, helping detect fractures, dislocations, loose bodies, cartilage loss, osteoarthritis and joint effusion. It’s commonly used in trauma assessment and alongside other views for surgical planning.

Place the patient in a lateral recumbent position with the affected side down (or supine with the opposite leg displaced). Flex the knee about 20–30° (up to 45° if needed) so the femoral condyles are superimposed and the patella is in profile. Align limb axis to the film and centre the X‑ray beam at the knee joint, including distal femur and proximal tibia.

The three standard knee X‑ray views are: anteroposterior (AP) — often weight‑bearing to assess joint space and alignment; lateral — shows sagittal profile, effusion and fractures; and axial (skyline/sunrise or Merchant) — evaluates the patellofemoral joint and patellar alignment. These complementary views help detect arthritis, fractures, dislocations and soft‑tissue concerns.

A skyline (axial or “sunrise”) X‑ray is a tangential view of the patella and trochlear groove obtained with the knee flexed. It highlights the patellofemoral joint surface, showing patellar alignment, chondral defects, fractures, subluxation, and joint-space narrowing. The projection improves detection of patellar fractures or maltracking that may be missed on standard frontal or lateral knee films.

A lateral view on an X-ray is a side-profile image taken with the X-ray beam directed from one side of the body to the other. It complements front-to-back views by showing depth and spatial relationships of bones and organs, helping detect displaced fractures, joint alignment, lung pathology, or fluid levels. The patient’s side is positioned against the detector with arms moved out of the field.

A lateral knee X‑ray can detect many bony signs of arthritis—osteophytes, joint-space narrowing, subchondral sclerosis and cysts—and helps assess patellofemoral and tibiofemoral alignment. However, X‑rays are insensitive to early cartilage loss, synovitis or subtle inflammatory changes; MRI is better for early or soft-tissue disease. Radiographs are useful for diagnosing and grading established osteoarthritis but require clinical correlation.