Hamstring Strain

  • Hamstrings: biceps femoris, semitendinosus, and semimembranosus (located on the back of the thigh and are responsible for extending (straightening) the hip and flexing (bending) the knee

  • Hamstring strains commonly occur when muscles are contracting forcefully while lengthening (eccentric contraction) which is seen during late swing phase of sprinting

    • Maximally lengthened muscle and working to decelerate hip flexion and knee extension to prepare for the foot to hit the ground → knee is swinging straight and hamstrings act as a break to slow knee extension before the foot hits

  • Overloading injuries typically occur in a lengthening position such as high speed running, when the hamstring is eccentrically contracting across the hip and knee and late in swing phase / early heel strike. 

    • Overloading injury typically involved the biceps femoris

  • Overstretching combined with hip flexion and knee extension such as kicking or reaching to pick up and lift something off the ground with knee extended 

    • Overstretching injuries - involves the proximal semimembranosus 

    • Hamstring muscles: biceps femoris, semitendinosus, semimembranosus 

  • Common in sprinters/jumpers and contact sports, most common in soccer players 

    • Rapid changes in direction and lifting objects from the ground 

  • Signs/Symptoms

    • Sudden mild to severe pain in posterior thigh, popping or tearing sensation description, swelling and bruising may be a delayed symptom

      • Grade I→ few muscle fibers are damaged, rarely influences muscle performance and endurance, stiffness in posterior thigh, normal gait and ROM

        • Small local pain area

        • Tightness and cramping in posterior thigh

        • Slight pain with muscle stretching &/or activation

        • Stiffness that may subside during activity but returns following

        • Minimal strength loss

      • Grade II → half of the muscle fibers are torn, acute pain, swelling, mild loss of muscle function, pain with palpation and knee bending, may have gait abnormalities

        • Local pain - larger area than grade I

        • Greater pain with stretching and/or activation

        • Stiffness/weakness and possible hemorrhaging and bruising

        • Limited ability to walk (24-48 hrs after injury)

      • Grade III → severe muscle weakness from more than half to full rupture of muscles, swelling and high pain levels

        • Diffuse swelling and bleeding

        • Possible palpable mass of muscle tissue at tear site

        • Extreme difficulty or inability to walk 

        • *Refer to physician* 

  • Hamstrings have higher percentage of type II fibers than other muscles → more susceptible to injury 

  • Anatomically → anterior pelvic tilt may place hamstring muscle group in a more lengthened position and increase risk of hamstring strain 

  • Healing phases: inflammation, proliferation, remodeling 

    • Inflammation (3-5 days)

      • Pain, swelling, bleeding and loss of ROM

    • Proliferation (lasts several weeks)

      • Muscle weakness, stiffness, swelling, and limited function 

    • Remodeling (up to 2 years - depending on extent of injury)

      • Early ROM and soft tissue mobilization after injury may help promote more organized scar formation with fever adhesions to surrounding tissue 

      • During this phase, individual will have minimal complaints and tolerate greater stress to muscle

  • Return to play/Reinjury Risk

    • High rates of recurrent Hamstring strain injuries are associated with substantial losses of time in training and competition for athletes

    • Lower risk of re-injury → when individuals performed agility and stability exercises after injury when compared to only stretching and strengthening