Causes / typical injury mechanism: Quadriceps contusions are due to compression from a nonpenetrating blunt force to the anterior thigh, either from an opponent's knee or from equipment, causing a muscle injury. This causes the formation of hematoma within the muscle, leading to pain, swelling, and loss of motion. This type of injury has a self-limited course; however, if not treated early, patients may have a prolonged disability time and develop myositis ossificans. The severity of injury can be determined by the degree of active knee flexion at the first 24-48 hours after the injury. Two major but rare complications that may result from quadriceps contusion are myositis ossificans and anterior thigh compartment syndrome.

Classic history and presentation:

• History of direct trauma to the thigh.
• Pain gets worse in the first 24-48 hours after trauma.
• Unable to bear weight on injured limb.
• Limited, painful knee range of motion (ROM).
• Swelling, point of tenderness, and ecchymosis / bruising seen in the anterior compartment of the thigh.
• Gait will range from normal to antalgic depending on injury severity.

Prevalence: The incident of quadriceps contusion is 12.1% of all sports injuries, and it is a common cause of morbidity in contact sports. The incidence is highest among athletes, especially those who participate in sports without wearing padding for the thigh or upper leg (ie, soccer and rugby). Quadriceps contusion is more likely to occur during a competitive event rather than practice, compared to quadriceps strain, which is more likely to occur during practice sessions. The incidence of myositis ossificans following a quadriceps contusion is 9%-12%.

Quadriceps contusion is twice as common in male patients compared to female patients.

Risk factors: Quadriceps contusion risk factors are participation in contact sports, high level of competition, lack of protective equipment use, athletic experience, and playing position. The most common sports associated with quadriceps contusion are football, soccer, and rugby.

Pathophysiology: This is caused by direct trauma to the anterior compartment of the thigh and compressing musculature into the femur. This injury causes muscle fiber tears, which forms a hematoma within the muscle, causing pain, swelling, and loss of motion.

Grade / classification system:
Jackson and Feagin classification –

• Grade 1: Mild, > 90 degrees ROM for knee flexion, patient is able to bend knee, normal gait.
• Grade 2: Moderate, 45-90 degrees ROM for knee flexion, patient is unable to bend knee or raise from chair, antalgic gait.
• Grade 3: Severe, < 45 degrees ROM for knee flexion, patient is unable to ambulate or bear weight on injured leg, effusion around the knee, antalgic gait.