Causes / typical injury mechanism: Proximal hamstring injuries are acute injuries secondary to rapid / forceful knee extension and hip flexion.

Classic history and presentation: History may include rapid acceleration and kicking sports such as sprinting, hurdling, soccer, and water skiing.

Prevalence: Up to 30% of acute athletic injuries involve the hamstrings. Professional soccer players injure their hamstrings at a rate of about 20% per season.

• Age – Skeletally mature athletes and "weekend warriors."
• Sex / gender – Male athletes are most commonly affected.

Risk factors: The biggest risk factor for proximal hamstring injuries is history of previous injury to this area. Other risk factors include hamstring-quadriceps strength ratio imbalance (< 0.6 hamstring-quadriceps strength), playing sports that involve rapid acceleration, kicking, and ballistic movement (most commonly soccer), core stability, lumbopelvic position, inadequate warm-up, muscle fatigue, age older than 25 years, and possibly reduced hip flexor flexibility.

Pathophysiology: Eccentric contraction of hamstrings while in position of maximum stretch leads to a continuum of injury ranging from myofibril disruption to disruption of the extracellular matrix and fascia, resulting in bleeding, retraction, and scar formation.

Grade / classification system: Proximal hamstring injuries are generally descriptive based upon MRI: number of tendons involved, amount of retraction from ischial tuberosity. Cohen et al described an MRI Scoring System for Hamstring Injuries that predicts time missed from competition. If the injury occurs in the muscle, a standard grading scheme of grade 1 (stretched), grade 2 (partial tear < 50% of muscle belly), or grade 3 (complete tear) may be used.