Synopsis

• Landing from a high jump (basketball and volleyball players)
• Sudden change in direction (football and soccer players)
• Long distance downhill running
• Falling backwards while feet are caught or fixed to the ground (elderly patients)

• Pain and dysfunction at the anterior thigh either immediately or within several days after injury; pain is worse with weight-bearing.
• Swelling and ecchymosis can be seen in more severe strains.

• Age – Mild to moderate strains most often occur in active young adults younger than 40 years. Ruptures are more common in patients older than 50 who have comorbidities such as diabetes mellitus, obesity, and hyperparathyroidism.
• Sex – Female patients are at 3 times increased risk compared to male patients.

• Current musculoskeletal injury of the leg, especially of the knee (eg, anterior cruciate ligament [ACL] tears) or hamstring, causing lack of coordinated movement between muscle groups.
• Use of fatigued muscles (rectus femoris is 65% type II muscle fibers). The dominant leg is more often affected.

• Grade 1 (mild) – No loss or minimal loss of strength, no palpable muscle defect on physical examination.
• Grade 2 (moderate) – Moderate loss of strength, may feel a small palpable muscle defect on physical examination of the anterior thigh.
• Grade 3 (severe) – Usually complete loss of strength, can often feel a palpable muscle defect.