MR-IMAGING APPEARANCE OF THE EXTENSOR MECHANISM OF THE KNEE - FUNCTIONAL-ANATOMY AND INJURY PATTERNS

Trauma to the extensor mechanism of the knee, a common clinical proble m, can be accurately evaluated with magnetic resonance (MR) imaging, T he extensor mechanism consists of the quadriceps muscle and tendon, pa tella, patellar tendon, and patellar retinacula, Injuries of these str uctures can be classified into partial and complete tears, Acute injur ies are associated with edema, hemorrhage, and fluid collections; chro nic injuries often demonstrate redundancy, atrophy, and retraction of the affected structures, MR imaging is useful in differentiating parti al and complete tears and in evaluating tissue edema and hemorrhage, I t also allows detection of unsuspected nondisplaced patellar fractures and chronic conditions due to repetitive trauma, Transient dislocatio n of the patella is an often clinically unsuspected entity for which M R imaging can serve an important diagnostic role, A detailed understan ding of the functional and anatomic relationships of the extensor mech anism can greatly assist in interpretation of MR images of the traumat ized knee.