Gastrocnemius


Original Editor Aarti Sareen

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Description

Gastrocnemius forms the major bulk at the back of lower leg and is a very powerful muscle. It is a two joint or biarticular muscle and has two heads and runs from back of knee to the heel.  It has a function in any ambulatory movement for example walking, running and jumping. Together with Soleus and Plantaris together forms the calf muscle or triceps surae. Occasionally there are sesamoid bones called "fabella" in the lateral head of gastrocnemius muscle.

Anatomy

Origin

The two heads unite into a broad aponeurosis which eventually joins with the deep tendon of the soleus to form the Achilles tendon at it insertion.

Medial head: from posterior nonarticular surface of medial femoral condyle

Lateral head: from lateral surface of femoral lateral condyle.

Insertion

The middle 1/3 of the posterior calcaneal surface.

Nerve supply

Tibial nerve (S1,S2)

Function

Powerful plantarflexion at ankle joint.

Flexion at knee joint.

Powefull planterflexor at ankel joint

Flexion at knee joint

As gastrocnemius is strong plantarflexion but enters a stage of passive insufficiency during full dorsiflexion of ankle joint when the knee is near it or in full extension. As the  knee flexion increases (soleus become more active). In the seated calf raise (knees flexed to 90º), the gastrocs are virtually inactive while the load is borne almost entirely by the soleus. 

The lateral and medial head of gastrocnemius muscle do not involve in the hip rotation but in and MRI study by Dr. Per Tesch (Sweden) suggests "toes in" activate both heads and "toes out" activate the medial head to a higher degree.

Assessment

Length

Gastrocnemius (outer calf towel stretch): Sit with both legs straight. Loop a towel around the ball of one foot and grasp each end of the  towel. Flex your foot back toward your ankle, toes toward your knee.

Begin this calf stretch with your hands against the wall and your leg to be stretched behind you as demonstrated (figure 4). Keep your heel down, knee straight and feet pointing forwards. Gently lunge forwards until you feel a stretch in the back of your calf or knee . Hold for 15 seconds and repeat 4 times at a mild to moderate stretch pain free.

Treatment

Trigger Point Refferal Pattren

The gastrocnemius may contain up to four trigger points.

• The two medial trigger points lie in the medial head of the gastrocnemius, with the upper trigger point found just below the crease of the knee, and the lower trigger point an inch or two below it.
• The two lateral trigger points in the lateral head mirror the positioning of the medial trigger points, except that they lie slightly more distal (towards the foot) by about a half-inch.

Resourses

See also

• Achilles rupture
• Achilles tendinopathy
• Achilles tendon
• Baker's cyst
• Calcaneal fracture
• Calf strain
  
• Deep vein thrombosis
• Fabella syndrome
• Thompson test
• Soleus

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Recent Related Research (from Pubmed)

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