When a patient presents with knee pain, a plain X-ray is almost always the first imaging investigation requested. Weight-bearing anteroposterior and lateral views provide a wealth of information: joint space narrowing indicating cartilage loss, osteophyte formation at the joint margins, subchondral sclerosis, and changes in bone alignment. For the experienced surgeon, these images tell a clear story about the state of the joint and help determine the most appropriate management pathway.
However, plain radiographs have meaningful limitations. Cartilage itself is not visible on X-ray — what the clinician sees is the space between bones, which acts as a proxy for cartilage thickness. Early cartilage damage may not produce any visible narrowing at all, meaning a patient with significant pain and functional limitation can have a seemingly normal X-ray. In these cases, MRI scanning provides a far more detailed picture of the soft tissues, including the menisci, ligaments, and articular cartilage surface.
CT scanning is occasionally used when precise bony anatomy is required, for example in planning complex osteotomies or revision procedures. Nuclear medicine bone scans can help identify areas of metabolic bone activity where the diagnosis remains uncertain.
The key message for patients is that imaging is one part of the clinical picture. A thorough history and examination remain the foundation of accurate diagnosis, and the findings on any scan must always be interpreted in the context of the individual’s symptoms and functional goals.
