[Medical Q&A] After a knee injury, the X-ray shows no fracture. Why does the doctor still recommend an MRI?

Planner: Chinese Medical Association

Reviewer: Han Liqiang, deputy chief physician, Tianjin Third Central Hospital

Many people go to the hospital for an X-ray after a knee injury. As long as the results show that the knee is not fractured, they think that everything is fine. However, sometimes doctors recommend further magnetic resonance imaging (MRI). MRI is a high-resolution imaging technology that can show soft tissue structures such as ligaments, tendons, and menisci in detail, which are often not clearly shown on X-rays.

The knee joint is the most complex joint in the human body. It is not just composed of bone, but also of surrounding cartilage, ligaments and meniscus. Unless a very large external force causes knee injury and fracture, most external forces rarely cause fractures, but are very likely to cause damage to surrounding tissues, the most common of which are meniscus, anterior/posterior cruciate ligaments and medial/lateral collateral ligament injuries. Once these tissues are damaged, many people experience discomfort and weakness in the knee joint, but this does not affect their normal walking, which is why the injury is easily overlooked. For ligament and meniscus injuries, doctors can make a basic diagnosis based on physical examinations, but the degree of injury often requires MRI examinations to further clarify, and the degree of injury is different, and the treatment methods are also different. Therefore, in order to further clarify the diagnosis and choose the appropriate treatment method, MRI examination of the knee joint is often essential.