Posterior compartment of the arm

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Posterior compartment of the arm
Cross-section through the middle of upper arm.
Artery profunda brachii
Nerve muscular branches of the radial nerve

The posterior compartment of the arm is an anatomic compartment which contains muscles which are all supplied by the radial nerve. This compartment is also known as the "extensor compartment", extension being its main action.


The muscles of this compartment are the triceps brachii and anconeus muscle.

  • The triceps brachii is a large muscle containing three heads (lateral, medial, and middle).
  • The anconeus is a small muscle stabilizes the elbow joint during movements. Some embryologists consider it as the fourth head of the triceps brachii. As the upper and lower limbs have similar embryological origins and the lower limb contains the quadriceps femoris muscle (the lower limb equivalent of the triceps), which has four heads, this would seem to make sense.

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