A single X-ray of the knee gives limited useful information because of the flat dimension. This A-P view hints at the patella and gives some information about the status of the actual joint but on its own it is of limited value.
X-rays are generally taken in at least three planes - both with the knee straight and with the knee bent:
- AP view - anteroposterior
- Lateral view
- Skyline or Sunrise view
This will allow the clinician to evaluate the bones two or three-dimensionally, and small fractures and other problems may be revealed that were not apparent with a single dimension.
Again less information is obtained if the patient is lying on the X-ray table, compared to standing up weight-bearing. The joint space may appear perfectly normal if the patient is lying down, suggesting that the menisci and joint cartilage are normal and filling the space, but a weight-bearing view may show the joint space to collapse on one side if these structures are damaged or missing.