Hamstring
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Image:Gray1239.png 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.
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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.
[edit] Human anatomy
The hamstring muscles are :
- semitendinosus - attaches proximally to the ischial tuberosity of the pelvis, and distally to Medial surface of tibia.
- semimembranosus - also attaches proximally to the ischial tuberosity and distally to the medial tibial condyle.
- biceps femoris - has a long and a short head, and only the long head is considered a hamstring. It attaches proximally to the ischial tuberosity and distally to the lateral side of the head of the fibula. The short head, while not actually a 'hamstring', has the same action as theses muscles. Its proximal attachment is to the linea aspera near the head of the femur, and it attaches distally via a common tendon with the long head, to the lateral tibial condyle.
The four muscles of the posterior thigh flex (bend) the knee and extend (straighten) the hip, three of which make up the hamstrings.
[edit] Innervation
The proper hamstrings, semitendinosus, semimembranosus, and the long head of biceps femoris, are innervated by the tibial division of the sciatic nerve (L5, S1, S2). The short head of biceps femoris is innervated separately by the common fibular division of the sciatic nerve (L5, S1, S2).
[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. Biceps femoris extends the hip as when beginning to walk; it also flexes the knee and laterally (outwardly) rotates the lower leg when the knee is bent. The hamstring plays a crucial role in many daily activities, such as, walking, running, jumping, and controlling some movement in the trunk. In walking, it is most important when contracting eccentrically (controlled lengthening of a muscle) to decelerate the forward swing of the leg.
[edit] Injuries
The first of which is the strain, which is also known as a pulled hamstring. Straining of the hamstring is defined as an excessive stretch of muscle fibers and related tissues.
- Third degree is the final stage and most intense, of hamstring strains. It includes a complete tear of the hamstring 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 completely healed before athletics or exercise is the best way to insure that an injury will not recur.
Another injury to the hamstring is the high hamstring tendinopathy. This condition consists of pain in the thigh or buttock. This injury is commonly seen in middle and long distance runners. The pain experienced with high hamstring tendinopathy is experienced when accelerating.
Although there are many ways a hamstring can be injured, it can be summed up by two words, strain or tear.
Not only does the hamstring help humans by running and flexing their knees, it helps in many other ways. One of those ways in which the hamstring helps is, arthroscopic surgery. With the new technology that is available in today’s society the hamstring is one of the most widely used assets in surgery. There is one major surgery that is becoming more popular that involves using the hamstring although it does not have to be injured to get use from it, in fact it has to be healthy. This surgery is called ACL reconstruction. The anterior cruciate ligament (ACL) is a ligament in the knee that helps hold the knee in place. During this procedure, doctors will take a sliver of the hamstring and put in the place of a torn ACL. The success rate of this surgery is very high because the hamstring is such a strong muscle and can have many different uses. When a hamstring is used to replace an ACL, it takes a few weeks to recover from the surgery. After the few weeks are up, it takes many months of physical therapy to insure that the hamstring is at full strength. This is done so that the hamstring can heal properly.
There are many ways that the hamstring can be strengthened. The main way is to exercise the hamstring. This can be done by running or lifting weights.
[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 mean the crippling of any effort, e.g. a person may be hamstrung in his/her studies by not being too bright.
