Hamstring Injuries in Athletes: Grading, Treatment, and Returning to Sport

Why Hamstring Injuries Are So Common — and So Prone to Recurrence

The hamstring muscle group — the biceps femoris (long and short heads), semimembranosus, and semitendinosus — runs along the back of the thigh and performs two critical functions: hip extension and knee flexion. During high-speed running, these muscles are under enormous eccentric load during the late swing phase, as they contract while lengthening to decelerate the swinging leg and prepare for ground contact. This combination of high speed, high force, and a lengthening muscle is the biomechanical context for the vast majority of hamstring strains in sport.

Hamstring injuries are among the most common soft tissue injuries in sprinting, soccer, Australian rules football, and American football. They are particularly problematic because of high recurrence rates — studies report that approximately one-third of hamstring strains recur within the first year of return to sport. Recurrence is associated with premature return, inadequate rehabilitation, and failure to address underlying risk factors including previous injury, muscle weakness, and fatigue.

Classifying the Injury

Hamstring injuries are graded by extent of tissue disruption:

Grade 1 (mild): A small number of muscle fibers are torn. The athlete experiences localized tightness and discomfort but maintains near-full strength and can often continue activity at reduced intensity. Return to sport typically takes seven to fourteen days.

Grade 2 (moderate): A partial tear with significant pain, tenderness, bruising, and measurable strength loss. The athlete cannot perform at their prior level. Return to sport takes three to six weeks with appropriate rehabilitation.

Grade 3 (severe): A complete or near-complete muscle tear. Significant swelling, bruising, and inability to contract the muscle characterize this injury. Complete proximal hamstring avulsions — where the tendon pulls off the ischial tuberosity — are a surgical condition that requires operative reattachment to achieve full recovery.

MRI is the most accurate tool for confirming injury grade, identifying which specific muscle is involved, and locating the tear (musculotendinous junction, proximal tendon, or myosin belly). Ultrasound can be useful for dynamic assessment and monitoring healing.

Treatment by Phase

Acute phase (days 0–7). The priority is reducing hemorrhage and swelling. Compressive bandaging, elevation, and ice application in the first 48 to 72 hours limit hematoma formation. Gentle pain-free range-of-motion exercise begins as soon as tolerated — complete immobilization leads to adhesion formation and prolongs recovery. Weight-bearing is allowed as tolerated for grade 1 and 2 injuries.

Subacute phase (week 2 onward). As pain subsides, progressive loading begins. Isometric hamstring exercises transition to eccentric strengthening — specifically the Nordic hamstring exercise, in which the athlete lowers their body forward from a kneeling position while contracting the hamstrings. Nordic curls have the strongest evidence base for both rehabilitation and prevention of hamstring injuries and should be a consistent component of the recovery program.

Hip extension strengthening (Romanian deadlifts, single-leg deadlifts, hip thrusts) addresses the full mechanical demands of sprinting and helps restore the strength symmetry between injured and uninjured sides.

Return-to-sport phase. Progressive running — from jogging to striding to full-speed sprints — is introduced when the athlete demonstrates pain-free eccentric strength within 10 to 15 percent of the uninjured side. Sport-specific agility and acceleration-deceleration drills complete the return protocol. Clearance is criteria-based, not time-based.

Preventing the Second Injury

The most consequential injury prevention strategy supported by strong evidence is the Nordic hamstring exercise protocol. Studies in professional soccer have shown a reduction in hamstring injury incidence of over 50 percent with consistent implementation of this training. Adequate rest between high-intensity sessions, pre-season fitness, and avoiding return to full-speed work before meeting objective strength criteria all reduce recurrence risk.

If you've sustained a hamstring injury, the specialists at Maryland Orthopedic Specialists can help. Call (301) 515-0900 or [schedule an appointment online](https://www.mdorthospecialists.com/contact).