A hamstring refers to any of the six tendons contracted by three posterior thigh muscles, the semitendinosus, semimembranosus and biceps femoris.
The term hamstring is also used to refer to the muscles themselves.
The hamstring tendons make up the borders of the space behind the knee.
The hamstring muscles are involved in knee flexion and hip extension.
The three muscles of the posterior thigh, the semitendinosus, semimembranosus, biceps femoris long and short head flex the knee.
All hamstring muscles, but the short head of biceps femoris, extend the hip.
The three true hamstring muscles cross both the hip and the knee joint and are therefore involved in knee flexion and hip extension.
The short head of the biceps femoris crosses only one joint, the knee, and is therefore not involved in hip extension, and because of it divergent origin and innervation it is sometimes excluded from the hamstring characterization.
The semitendinosus muscle originates at the ischial tuberosity, inserts at the medial surface of tibia, and is innervated by the tibial nerve.
The semimembranosus muscle originates at the ischial tuberosity, inserts at the medial tibial condyle, and is innervated by the tibial nerve.
The biceps femoris long head originates at the ischial tuberosity, inserts at the lateral side of the head of the fibula, and is innervated by the tibial nerve.
The biceps femoris short head originates at the linea aspera and lateral supracondylar line of femur, inserts
at the lateral side of the head of the fibula with the long head, and is innervated by the common peroneal nerve.
The hamstrings cross and act upon two joints, the hip and the knee.
Semitendinosus and semimembranosus extend the hip when the trunk is fixed.
Semitendinosus and semimembranosus also flex the knee and medially rotate the lower leg when the knee is bent.
The long head of the biceps femoris extends the hip.
The short and long heads flex the knee and outwardly and rotates the lower leg when the knee is bent.
The hamstrings muscles play a role in many daily activities, such as, walking, running, jumping, and controlling some movement in the trunk.
The hamstring muscles with are most important as an antagonist to the quadriceps in the deceleration of knee extension.
Hamstring muscles are usually imaged with an ultrasound and/or MRI and are useful in establishing the grade of strain, or if the muscle is completely torn.
Of the hamstring muscles the biceps femoris is most commonly injured, followed by the semitendinosus.
Injury to the semimembranosus muscle is rare.
The level and degree of retraction can be determined, and injuries with a hamstring strain of greater than 60mm in length have a greater risk of recurrence.
The distal semitendinosus tendon can be used in the surgical procedure ACL reconstruction.
Hamstring strain strike athletes of all types.
During a hamstring strain, one or more of the muscles gets overloaded, and might even start to tear.
Hamstring strain likely to occur during activities that involve a lot of running and jumping or sudden stopping and starting.
Reducing risk for hamstring injury by warm ups prior to exercising.
Severe hamstring strains ca lead to pain and inability to walk or stand.
Symptoms of hamstring injury include; pain during exercise, along with a snapping or popping feeling, pain in the back of the thigh and lower buttock when walking, straightening the leg, or bending over, tenderness, or bruising.
Minor to moderate hamstring strains usually heal over time, on their own.
Treatment includes: rest, avoiding putting weight on the leg, icing,compression bandages, leg elevation, NSAID’s, stretching and strengthening exercises.
In severe cases where the muscle is torn,surgery may be needed.