In anatomy, extension is a movement of a joint that increases the angle between two bones or body surfaces at a joint. Extension usually results in straightening of the bones or body surfaces involved. For example, extension is produced by extending the flexed (bent) elbow. Straightening of the arm would require extension at the elbow joint. If the head is tilted all the way back, the neck is said to be extended.

Muscles of extension

Upper limb

*of arm at shoulder **Axilla and Shoulder ***

Latissimus Dorsi The latissimus dorsi () is a large, flat muscle on the back that stretches to the sides, behind the arm, and is partly covered by the trapezius on the back near the midline. The word latissimus dorsi (plural: ''latissimi dorsorum'') comes from L ...

*** Posterior Fibres of Deltoid *** Teres Major *of forearm at elbow ** Posterior compartment of the arm *** Triceps Brachii *** Anconeus *of

hand A hand is a prehensile, multi-fingered appendage located at the end of the forearm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs. A few other vertebrates such as the koala (which has two opposable thumbs on each "h ...

at wrist ** Posterior compartment of the forearm ***

Extensor carpi radialis longus A hand is a prehensile, multi-fingered appendage located at the end of the forearm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs. A few other vertebrates such as the koala (which has two opposable thumbs on each "hand ...

*** Extensor carpi radialis brevis *** Extensor carpi ulnaris *** Extensor digitorum *of

phalanges The phalanges (singular: ''phalanx'' ) are digital bones in the hands and feet of most vertebrates. In primates, the thumbs and big toes have two phalanges while the other digits have three phalanges. The phalanges are classed as long bones. ...

, at all joints ** Posterior compartment of the forearm *** Extensor digitorum *** Extensor digiti minimi (little finger only) ***

Extensor indicis In human anatomy, the extensor indicis roprius'' is a narrow, elongated skeletal muscle in the deep layer of the dorsal forearm, placed medial to, and parallel with, the extensor pollicis longus. Its tendon goes to the index finger, which it e ...

(index finger only) *of

, at interphalangeal joints ** Lumbricals of the hand ** Dorsal interossei of the hand ** Palmar interossei *of

thumb The thumb is the first digit of the hand, next to the index finger. When a person is standing in the medical anatomical position (where the palm is facing to the front), the thumb is the outermost digit. The Medical Latin English noun for thumb ...

** Extensor pollicis brevis (proximal phalange) ** Extensor pollicis longus (distal phalange)

Lower limb

Hip

*of thigh/ femur at

hip In vertebrate anatomy, hip (or "coxa"Latin ''coxa'' was used by Celsus in the sense "hip", but by Pliny the Elder in the sense "hip bone" (Diab, p 77) in medical terminology) refers to either an anatomical region or a joint. The hip region is ...

Gluteus maximus The gluteus maximus is the main extensor muscle of the hip. It is the largest and outermost of the three gluteal muscles and makes up a large part of the shape and appearance of each side of the hips. It is the single largest muscle in the human ...

** Posterior compartment of thigh *** Biceps femoris *** Semitendinosus *** Semimembranosus

Knee

*of leg at

knee In humans and other primates, the knee joins the thigh with the leg and consists of two joints: one between the femur and tibia (tibiofemoral joint), and one between the femur and patella (patellofemoral joint). It is the largest joint in the hu ...

(L3-L4) ** Quadriceps *** Rectus femoris muscle *** Vastus medialis *** Vastus lateralis *** Vastus intermedius

Toes

*of toesFoot Articulations
/ref> ** Extensor hallucis longus ** Extensor digitorum longus ** Extensor digitorum brevis ** Extensor hallucis brevis

References

{{Joints Anatomical terms of motion *