Thomas H. Trojian, MD^abc∗

^aOrthopaedics, UCHC/NEMSI, Farmington, CT, USA. E-mail address: ttrojian@uchc.edu

^bFamily Medicine, UCHC, Farmington, CT, USA

^cDepartment of Athletics, University of Connecticut, Storrs, CT, USA

^∗99 Woodland Street, Hartford, CT 06105.

Muscle injuries are common problem in sports, with contusions being reported as 12.1% of all injuries.¹ Muscle contusions are more frequently seen in males (15.1%) than in females (6.3%).¹ Sports such as American football, soccer, and softball have a higher frequency of muscle injuries.² In high school sports, boys are more likely to suffer contusions than girls.² Contusion injuries are more likely (per athletic exposure) to occur during games than during practice.³ The locations of contusions are not listed by body parts in epidemiology studies, but contusions are reported to comprise 14.2% of all thigh injuries in high school sports (15.8% in boys and 11.2% in girls)¹ and 19% of all muscle injuries in professional soccer.³ Jackson and Feagin⁴ reported that the average return to duty without proper treatment of thigh contusions was 45 days. Therefore thigh contusions are a common problem in sports, which can cause prolonged disability without proper treatment.

A thigh contusion occurs when a compressive force applied to the quadriceps muscle is not dispersed, and the muscle and underlying tissue is squeezed into the femur. The myofibers and capillaries rupture. Because the thigh has a large potential space, a large hematoma can develop; therefore, proper treatment from the beginning is important.⁵

When a thigh contusion occurs the muscle heals by a repair process, not a regenerative process as occurs in bone.5,6 The tissue does not return to the original state, and scar is present. Repair occurs in 3 overlapping phases: (1) destruction phase (0–7 days), (2) repair phase (7–21 days), and (3) remodeling phase (>21 days).⁶

The repair of the skeletal muscle, including the formation of a fibrotic scar following injury, depends on numerous factors.⁷ The activity of 2 cell types, myosatellite cells and fibroblasts, may be the determining variable in deciding the ultimate fate of the injured skeletal muscle. Myosatellite cells become myoblasts and repair muscle by fusing with injured, but surviving myofibers, or by de novo formation of new myotubes to form new myofibers.⁷ After injury, fibroblasts proliferate in the area of the damaged muscle and begin to produce a collagen-rich extracellular matrix to restore the muscle’s connective tissue framework.^8,9 Activated fibroblasts also release chemoattractants, which recruit additional fibroblasts and inflammatory cells to the injured tissue.^10,11 Excess proliferation and activation of fibroblasts can lead to unwanted unnecessary fibrosis and dense scar tissue, which can obstruct the muscle’s regenerative process and result in incomplete recovery.¹²

One of the important chemoattractants is transforming growth factor (TGF)-β1, which comes from macrophages and is responsible for the increased production of collagen and extracellular matrix. Interferon-γ has been shown to not only downregulate endogenous collagen expression but also to effectively block TGF-β1–mediated increases in collagen protein levels. Increased interferon-γ induces SMAD-7, which, via a negative feedback loop, reduces TGF-β1.¹¹

The mechanism of injury is a compressive force to the thigh. This force usually causes disability that prevents further play, but frequently the injury can be less severe and will not limit the athlete until after completion of play, when the bleeding and swelling has reached a tipping point. History of trauma with pain and limp are very common. If treatment is delayed or the injury is severe, compartment syndrome needs to be considered.

Certain features are very important in the history and physical examination of thigh muscle contusion. Alonso and colleagues have developed a prognostic algorithm to determine the number of days until full training. From the history, the ability to play following injury (yes or no beyond 5 minutes) and the number of hours between injury and presentation for treatment are important. Physical examination should record degrees of knee flexion on both legs, firmness rating from −5 to +5 of injured muscle, and circumference of thigh at suprapatelllar border in both legs.

DFT = 0.05 (DROM) + 0.73 (FR) + 1.34 (DC1) − 3.21 (Able to play) − 0.04 (hours) + 4.32¹³

where DFT = days between presentation for treatment and return to full training, DROM = uninjured-injured interlimb difference in knee flexion range (degrees), FR = firmness rating of the injured muscle on −5 to +5 scale, DC1 = injured-uninjured circumference difference at the suprapatellar border (cm), Able to play = ability to carry on playing following injury (0 = No, 1 = Yes), and hours = hours between injury and presentation.

Compartment syndrome caused by bleeding into the thigh compartments needs to be considered. The thigh is divided into anterior and posterior compartments by the medial and lateral intermuscular septa. The anterior compartment contains the femoral nerve, which innervates all of the muscles of the compartment, and provides sensation over the area of the knee, medial leg, and foot via the saphenous nerve.¹⁴ Intracompartment pressures are indicated if signs of compartment syndrome are found (pain, pulselessness, paresthesia, paralysis). In thigh contusions that developed anterior thigh compartment syndromes, Mithofer and colleagues¹⁵ reported that an excessively painful, tensely swollen thigh was seen in all patients; with pain with passive stretch in 100%; 60% of patients had paresthesia, 7% had pulselessness, and 40% had paralysis. Compartment pressures of 30 mm Hg or higher are suggested for surgical intervention.¹⁴

Ultrasonography has several important potential advantages over magnetic resonance imaging (MRI), such as superior spatial resolution, cost, convenience, portability, and dynamic evaluation of the injury.¹⁶ In a study by Megliola and colleagues¹⁷ where ultrasonography was compared with MRI, there were 8 minor and 29 severe contusions (functional loss, strength reduction, muscle hypertonia, and increased muscle volume proportional to pain intensity) examined by ultrasonography performed after the injury (6–72 hours after injury) and by MRI within 5 days. Ultrasonography identified all of the 29 severe contusions and 7 of the 8 minor contusions, with the extra days MRI was capable of detecting swelling and muscle injury that may have been missed on the initial ultrasonogram.¹⁷ Therefore, ultrasonography appears to be an equivalent method of identifying muscle contusion injury, and has the advantage of allowing aspiration of hematoma and serial evaluation.^18,19 Ultrasonography should thus be considered the first-line imaging tool for thigh contusion.¹⁷

On ultrasonography, thigh contusion is characterized by discontinuity of normal muscle architecture with ill-defined hyperechogenicity. This appearance may cross fascial boundaries, different to that of muscle strains. MRI typically demonstrates a feathery appearance of diffuse edema on short-tau inversion recovery and fat-suppressed T2-weighted images. Hematoma will be hypoechogenic on ultrasonography but will show an increased signal on MRI. Acute hematomas (<48 hours) are typically isointense on T1-weighted images, and subacute hematomas (<30 days) appear hyperintense relative to muscle on both T1-weighted and fluid-sensitive sequences, secondary to methemoglobin accumulation.18,20