Glossary
Hamstrings
Quick answer
The hamstrings are the three muscles at the back of the thigh. They bend the knee, help straighten the hip and act as a natural partner to the ACL by stopping the shin sliding forward, as Doha knee surgeon Dr. Pablo Gelber of Aman Hospital explains.
What they are
The three hamstrings are the biceps femoris on the outer side and the semitendinosus and semimembranosus on the inner side. They start at the sitting bone of the pelvis and cross the back of the knee. The biceps femoris attaches to the head of the fibula; the inner two attach to the tibia, the semitendinosus as part of the pes anserinus. You can feel their tendons as cords on either side behind a bent knee.
Why they matter for patients
Strong, well-timed hamstrings help control the knee during landing and cutting and reduce strain on the ACL. ACL injury prevention programmes, such as those used in football, include hamstring strengthening for this reason.
The semitendinosus and gracilis tendons are among the most commonly used grafts for ACL reconstruction. After harvest, the remaining muscles take over much of the work and strength is rebuilt with rehabilitation. Tight hamstrings can stop the knee straightening fully and add to front knee pain, and tendon irritation or a strain near the knee can cause pain behind or on the inner side of the knee.
Frequently asked questions
Will taking a hamstring graft make my leg weaker?
There can be a small, measurable change in deep knee-bending strength, but most people regain good function with rehabilitation. Your surgeon will discuss graft choice for your sport and needs.
Can tight hamstrings cause knee pain?
They can contribute, by limiting full straightening and increasing load on the front of the knee. Stretching and strengthening are often part of treatment for front knee pain.
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