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TRAUMATIC INJURIES, IN THE CONTEXT OF musculoskeletal medicine, can be classified as being either acute or chronic. Acute trauma entails a single, sudden traumatic event, whereas chronic trauma pertains to a series of traumatic events stemming from overuse of a certain joint or muscle group. Soft tissue injury resulting from acute trauma implicates many different supporting structures of the musculoskeletal system, which may include muscle, ligament, tendon, cartilage, or even fascia.
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Acute muscle trauma has been reported as the most common injury in athletes, with contusions and strain injuries accounting for about 90% of sports-related injuries.1 Internal joint derangement and joint dislocations are also common injuries to soft tissue resulting from acute trauma. At the knee, injury to the anterior cruciate ligament (ACL) is estimated to have an annual incidence of about 1 in 3,500 people.2 Shoulder dislocations have an estimated incidence rate of 23.9 per 100,000 person-years, with about 49% of the injuries occurring during a sport or recreational activity.3
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Muscular contusions result from direct, blunt trauma to the muscle, which causes micro-hemorrhaging and swelling within the belly of the muscle.4 In more severe contusions there is an increased risk for hematoma formation.4 Complications from muscular contusions can include acute compartment syndrome, myositis ossificans, and myonecrosis, depending on the severity of the injury.5 Joint dislocations and derangement are injuries that commonly occur when a force is directed through the joint, causing failure of the supporting soft tissue structures. For example, the “unhappy triad” of the knee describes the frequently combined injuries to the medial collateral ligament (MCL), medial meniscus, and ACL.6
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Diagnosis of muscular contusion is usually made based on the history, usually insidious onset, and physical examination; however, imaging of the site may be warranted if the healing process fails to proceed as expected. Patients will commonly present with pain at the site of trauma, limiting their range of motion in the affected limb. Plain radiographs are helpful to rule out an underlying fracture but are not as effective as magnetic resonance imaging (MRI) in assessing injury to the soft tissue. Acute compartment syndrome should be suspected when the soft tissue is firm or hard to palpation on physical examination. Diagnosis of derangement at a joint is suspected with pain and joint laxity on exam but is confirmed with MRI. Diagnosis of dislocation is made based on physical exam and plain radiographs. Table 32–1 describes different imaging modalities for various injuries associated with acute trauma.
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