Acute Hamstring Injury

Acute hamstring injury is a sudden strain or tear of the hamstring muscles or tendons, usually during sprinting or high-speed kicking, and is one of the most common time-loss injuries in running and pivoting sports.

In the UEFA Elite Club Injury Study, hamstring injuries made up 24% of all injuries in men's professional football in the most recent season studied, double the proportion 2 decades earlier.

It is a different condition from proximal hamstring tendinopathy, which causes gradual, load-related ischial pain. Older age and a previous hamstring injury are the strongest risk factors.

The hamstrings arise from the ischial tuberosity:

• •Biceps femoris long head (BFLH) and semitendinosus share a conjoint tendon origin
• •Semimembranosus has a separate, broader origin lateral to it
• •Biceps femoris short head arises from the linea aspera and is the only hamstring not crossing the hip

Innervation is sciatic: the tibial division supplies semimembranosus, semitendinosus and BFLH, the common peroneal division the short head. BFLH is most often injured in sprinting.

The BFLH central tendon runs through the muscle belly. Injuries that involve it behave more like tendon injuries, with a longer recovery.

Askling described 2 mechanisms:

• •Sprinting type (more common): high-speed eccentric loading in late swing, typically BFLH at the musculotendinous junction
• •Stretching type: slow end-range hip flexion with the knee extended (high kicks, dance, splits), typically the proximal free tendon of semimembranosus, with a longer recovery

Risk factors: older age and any previous hamstring injury are the strongest, and a recent one carries the highest risk. Previous anterior cruciate ligament injury and previous calf strain also raise risk, and factors related to running and hamstring strength are consistently associated.