Traumatic musculotendinous injuries of the knee: Diagnosis with MR imaging

Magnetic resonance (MR) imaging is the imaging modality of choice for evalu ation of acute traumatic musculotendinous injuries of the knee. Three discr ete categories of acute injuries to the musculotendinous unit can be define d: muscle contusion, myotendinous strain, and tendon avulsion. Among the qu adriceps muscles, the rectus femoris is the most susceptible to injury at t he myotendinous junction due to its superficial location, predominance of t ype II fibers, eccentric muscle action, and extension across two joints. Am ong the muscles of the pes anserinus, the sartorius is the most susceptible to strain injury due to its superficial location and biarticular course. T he classic fusiform configuration of the semimembranosus along with a prope nsity for eccentric actions also make it prone to strain injury. MR imaging findings associated with rupture of the iliotibial tract include discontin uity and edema, which are best noted on coronal images. The same mechanism of injury that tears the arcuate ligament from its fibular insertion can Th e gastrocnemius also result in avulsion injury of the biceps femoris. muscl e is prone to strain injury due to its action across two joints and its sup erficial location. Injuries of the muscle belly and myotendinous junction o f the popliteus are far more common than tendinous injuries.