Hamstring
Posterior view of left lower extremity.
Interior muscular view of the three muscles that make up the hamstring
Gray's	subject #128 478
Origin	tuberosity of the ischium, linea aspera
Insertion	tibia, fibula
Artery	inferior gluteal artery, profunda femoris artery
Nerve	sciatic nerve, tibial nerve[1]
Actions	flexion of knee
Antagonist	Rectus femoris muscle

In human anatomy, the hamstring refers to one of the three posterior thigh muscles, or to the tendons that make up the borders of the space behind the knee. In modern anatomical contexts, however, they usually refer to the posterior thigh muscles, or 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.

Contents 1 Etymology 2 Functions 3 Injury 4 Use in surgery 5 Training 6 See also 7 References 8 External links

[edit] Etymology

The word ham originally referred to the fat and muscle 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.

Another commonly accepted origin is that legs of ham used to be hung by a hook through the space between the thighbone and the tendons behind the knee. Ham/pork used to be more common in England than beef and lamb.

The four muscles of the posterior thigh (semitendinosus, semimembranosus, biceps femoris long & short head) flex (bend) the knee, while three of the four extend (straighten) the hip. The three 'true' hamstrings 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 (knee) and is therefore not involved in hip extension. With its divergent origin and innervation it is sometimes excluded from the 'hamstring' characterization.^[2]

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 side of the head of the fibula (common tendon with the long head)	common fibular

A portion of the adductor magnus is sometimes considered a part of the hamstrings.^[2]

[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; 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] Injury

Straining of the hamstring, also known as a pulled hamstring, is defined as an excessive stretch or tear of muscle fibers and related tissues. Such injuries are very common in several sports and the common phrase "to be hamstrung" arises from this kind of injury and its potential to sideline an otherwise-healthy athlete.^{[citation needed]} Hamstring injuries may result when an individual's training strengthens the quadriceps to the point where they become out of balance with the hamstrings, so that a powerful contraction from the quadriceps injures the hamstrings.

[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] Training

In strength training, the hamstrings are trained in isolation with the leg curl exercise, as well as a part of several other lower body exercises.

[edit] See also

• Hamstringing
• Popliteal fossa
• Lombard's Paradox

[edit] References

[edit] External links

• Illustration at ucla.edu
• Hamstring at eMedicine Dictionary

v • d • e List of muscles of lower limbs (TA A04.7, GA 4.465) ILIAC Region / ILIOPSOAS psoas major/psoas minor · iliacus BUTTOCKS gluteals: (maximus, medius, minimus) · tensor fasciae latae lateral rotator group: quadratus femoris · inferior gemellus · obturator internus · superior gemellus · piriformis THIGH / compartments Anterior sartorius · quadriceps (rectus femoris, vastus lateralis, vastus intermedius, vastus medialis) · articularis genu Posterior/hamstring biceps femoris · semitendinosus · semimembranosus Medial pectineus · obturator externus · gracilis · adductor (longus, brevis, magnus) Fascia Femoral sheath (Femoral canal) · Femoral ring Adductor canal · Adductor hiatus fascia lata (Iliotibial tract, Lateral intermuscular septum of thigh, Medial intermuscular septum of thigh, Fascia cribrosa/Saphenous opening) LEG/ Crus/ compartments Anterior tibialis anterior · extensor hallucis longus · extensor digitorum longus · peroneus tertius Posterior superficial · triceps surae (gastrocnemius, soleus, Achilles tendon) · plantaris deep · tarsal tunnel (flexor hallucis longus, flexor digitorum longus, tibialis posterior) · popliteus Lateral peroneus muscles (longus, brevis) Fascia Pes anserinus crural fascia (Anterior crural intermuscular septum, Posterior crural intermuscular septum, Transverse intermuscular septum) FOOT Dorsal extensor hallucis brevis · extensor digitorum brevis Plantar 1st layer (abductor hallucis, flexor digitorum brevis, abductor digiti minimi) · 2nd layer (quadratus plantae, lumbrical muscle) · 3rd layer (flexor hallucis brevis, adductor hallucis, flexor digiti minimi brevis) · 4th layer (dorsal interossei, plantar interossei) Fascia Plantar fascia retinacula (Peroneal, Inferior extensor, Superior extensor, Flexor)