Hamstring
From Wikipedia, the free encyclopedia
| Hamstring | ||
|---|---|---|
 |
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| Back of left lower extremity. | ||
| Origin: | tuberosity of the ischium, linea aspera | |
| Insertion: | tibia, fibula | |
| Artery: | inferior gluteal artery, profunda femoris artery | |
| Nerve: | sciatic nerve, tibial nerve[1] | |
| Action: | flexion of knee | |
| Antagonist: | Rectus femoris muscle | |
| Dorlands/Elsevier | h_02/12407578 | |
In human anatomy, a hamstring refers to one of the tendons that makes up the borders of the space behind the knee. In modern anatomical contexts, however, they usually refer to the tendons of the semitendinosus, the semimembranosus, and the biceps femoris. In quadrupeds, it refers to the single large tendon found behind the knee or comparable area.
As shown in the diagram, the human hamstring occupies the posterior of the body of the femur.
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[edit] Etymology
The word ham originally referred to the hollow behind the knee. String refers to tendons, and thus, the hamstrings are the string-like tendons felt on either side of the back of the knee.
The four muscles of the posterior thigh flex (bend) the knee, while three of the four extend (straighten) the hip. The short head of the biceps femoris, with its divergent origin and innervation, is not involved in hip extension, and thus is sometimes excluded from the 'hamstring' characterization.
| Muscle | Origin | Insertion | Nerve |
| semitendinosus | ischial tuberosity | medial surface of tibia | tibial |
| semimembranosus | ischial tuberosity | medial tibial condyle | tibial |
| biceps femoris - long head | ischial tuberosity | lateral side of the head of the fibula | tibial |
| biceps femoris - short head | linea aspera near the head of the femur | lateral tibial condyle (common tendon with the long head) | common fibular |
[edit] Functions
The hamstrings cross and act upon two joints - the hip and the knee.
Semitendinosus and semimembranosus extend the hip when the trunk is fixed or extend the trunk when the hip is fixed; they also flex the knee and medially (inwardly) rotate the lower leg when the knee is bent.
The long head of the biceps femoris extends the hip as when beginning to walk; both short and long heads flex the knee and laterally (outwardly) rotates the lower leg when the knee is bent.
The hamstrings play a crucial role in many daily activities, such as, walking, running, jumping, and controlling some movement in the trunk. In walking, they are most important as an antagonist to the quadriceps in the deceleration of knee extension.
[edit] Injuries
Straining of the hamstring, also known as a pulled hamstring, is defined as an excessive stretch of muscle fibers and related tissues. A third degree strain is the most intense, of hamstring strains. It indicates a complete tear of the hamstrings muscles. The tear can be felt with an individual’s hand. There is discoloration and intense pain. Third degree strains are a rare occurrence.
Hamstring strains occur in many different ways, but most often when the muscles are weakened. A hamstring strain most likely occurs during some athletic activity or some sort of exercise. If there is strain on the hamstring and the individual continues athletic activity or exercise on it, the hamstring continues to strain further and further.
Treating a hamstring strain can differ depending upon the severity of the injury. For a first degree strain, ice and resting it with some elevation is the best way to treat it. For a second degree strain, ice, rest, and elevation are also necessary. However, a second degree strain will take around two to three weeks to heal. A third degree strain should be treated the same as first and second degree strains but may take longer to heal, around three to six weeks. Crutches may be necessary for a third degree strain. Waiting until the muscle is completely healed before athletics or exercise is the best way to insure that an injury will not recur.
[edit] Use in surgery
The distal semitendinosis tendon is one of the tendons that can be used in the surgical procedure ACL reconstruction. In this procedure, a piece of it is used to replace the anterior cruciate ligament (ACL). The ACL is one of the four major ligaments in the knee.
[edit] Hamstringing
The original definition of "hamstringing" was to cut the hamstring of a person or animal, thus crippling them. It was generally in the context of war, and would cripple the victim, leaving him unable to fight. The hamstringing of a horse would make it incapable of using its rear legs, even for standing up, thus making it easier to kill. The definition has been extended to use as a metaphor to refer to the crippling of any effort, e.g. a person may be hamstrung in his/her studies by not being too bright.
