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Radiologic evaluation of the acutely painful knee in adults

Shahla Modarresi, MD
Cecilia Matilda Jude, MD
Section Editors
Robert H Shmerling, MD
Karl B Fields, MD
Deputy Editor
Monica Ramirez Curtis, MD, MPH


The knee is one of the largest and most complex joints in the body. It is lined by synovium and consists of two hinge-type joints between the femoral condyles and the medial and lateral tibial plateaus and of a gliding-type joint between the patella and the trochlear groove of the anterior distal femur (figure 1) [1,2]. The major stabilizers of the joint are the extensor tendons (quadriceps and patellar tendons), the medial and lateral collateral ligament complex, and the cruciate ligaments. The menisci are fibrocartilaginous structures that distribute the stress over the articular cartilage, absorb the shock in axial loading, stabilize the joint in flexion and extension, and have a role in joint lubrication [3].

Acute knee pain is caused by trauma in the majority of cases. Infection is the next major etiology for acute knee pain, followed by crystal-associated inflammation. Imaging modalities used to evaluate adults with acute knee pain and the appropriateness of particular imaging studies in these more common clinical scenarios will be reviewed here. The history and physical examination, which are necessary to develop a differential diagnosis prior to the selection of imaging tests, as well as a general review of imaging tests that are used in the evaluation of bone and joint pain, are presented separately. (See "Approach to the adult with unspecified knee pain" and "Imaging techniques for evaluation of the painful joint".)

Chronic knee pain is commonly caused by arthritis, bursitis, and cystic lesions around the joint; tendon pathology; cartilage pathology; chronic infection; osteonecrosis (avascular necrosis); stress fractures; and avulsion injuries. Radiologic evaluation of chronic knee pain is presented elsewhere. (See "Radiologic evaluation of the chronically painful knee in adults".)

The use of imaging in the assessment of children and adolescents with knee pain is also presented elsewhere. (See "Approach to acute knee pain and injury in children and skeletally immature adolescents" and "Approach to chronic knee pain or injury in children or skeletally immature adolescents".)


The knee is vulnerable to direct trauma. Most acute injuries sustained during adolescence and adulthood are caused by athletic activities, motor vehicle accidents, or falls. The most common injuries involve the soft tissues, including ligaments, cartilage, and menisci. Knee fractures are more common than dislocations. Radiological evaluation plays a major role in the diagnosis of knee injuries.

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Literature review current through: Nov 2017. | This topic last updated: Oct 11, 2017.
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