Triceps BrachiiEdit

The triceps brachii is the large extensor muscle on the back of the upper arm. It has three heads that converge into a single tendon inserting on the olecranon of the ulna, making it the primary muscle responsible for extending the elbow. The long head crosses the glenohumeral joint, giving it a secondary role in shoulder extension and adduction. Together, the heads stabilize the elbow during pushing and throwing motions and contribute to various upper-limb activities in daily life and sport.

Anatomy

Origins - Long head: infraglenoid tubercle of the scapula, which places it across the shoulder joint and allows a modest role in shoulder movement. - Lateral head: posterior aspect of the humerus, superior to the radial groove. - Medial head: posterior aspect of the humerus, inferior to the radial groove.

Insertions - All heads converge into a common tendon that attaches to the olecranon process of the ulna. The tendon may blend with surrounding structures such as the anconeus near the elbow.

Innervation and blood supply - Innervation is via the radial nerve, typically receiving contributions from C6–C8 spinal levels. The nerve travels with the posterior compartment of the arm to reach the muscle. - Vascular supply is primarily through the profunda brachii (deep brachial) artery, with accompanying veins. This blood supply reaches the muscle throughout its length, supporting function during contraction.

Anatomical variations - A rare accessory head of the triceps brachii can be present in some individuals, originating from one of several nearby sites on the humerus or adjacent soft tissues. Such variants may alter the apparent muscular bulk or the pattern of tendon insertion but generally do not change the fundamental actions of the muscle. - Variation in tendon architecture and attachment points can influence the mechanics of elbow extension and how the muscle is recruited during different movements.

Function

Primary actions - Elbow extension: the triceps brachii is the chief extensor of the elbow joint, providing the force needed to push objects away from the body or to straighten the arm after flexion. - Shoulder involvement: the long head crosses the shoulder joint and can assist with shoulder extension and, to a lesser degree, adduction when the arm is in certain positions.

Muscle recruitment and mechanics - During pushing movements, such as a bench press or push-up where the elbow is near full extension, the triceps acts as a key stabilizer and propulsive muscle. - In throwing and punching actions, the triceps helps accelerate the forearm and contributes to finished extension at the elbow. - The different heads are recruited in a synergistic pattern depending on elbow angle and shoulder position; training that targets all three heads can optimize overall elbow extension strength.

Clinical significance

Injury and pathology - Triceps tendon injuries range from tendinopathy to acute ruptures. Proximal ruptures near the olecranon are relatively rare but can occur with forceful elbow extension, eccentric loading, or in older individuals with degenerative changes. Such injuries typically present with weakness in elbow extension and a palpable defect near the elbow. - Distal triceps ruptures or avulsions are less common but may occur with heavy resistance or direct trauma. Accurate diagnosis often relies on physical examination supported by imaging.

Nerve and vascular considerations - Since the radial nerve innervates the triceps, injuries to the radial nerve in the arm or near the axilla can impair elbow extension and overall arm function. In cases of high radial nerve injury, weakness of elbow extension may be accompanied by wrist drop and sensory changes along the posterior arm and forearm.

Imaging and assessment - Ultrasonography and magnetic resonance imaging (MRI) are used to evaluate triceps muscle integrity, tendon health, and nerve involvement when a lesion is suspected. - Strength testing for elbow extension with the shoulder in different positions helps determine the functional status of the triceps and adjacent musculature.

Development and variation - The triceps brachii develops from the limb buds in embryonic development, as part of the posterior compartment musculature of the upper limb. Variation in head number and tendon insertion is a normal anatomical variation observed across populations and can influence local biomechanics.

Training, rehabilitation, and practical considerations

Strengthening and conditioning - Common exercises for the triceps include pushing and extension movements that load elbow extension, such as triceps pushdowns, overhead extensions, and skull crushers. Balanced training should ensure all three heads are engaged, with attention to elbow health and shoulder alignment. - Rehabilitation after an injury or surgery emphasizes gradual restoration of range of motion, progressive loading, and neuromuscular control to reestablish coordinated elbow extension while protecting healing structures.

Biomechanical considerations - The long head’s attachment to the scapula means shoulder position can influence triceps function. Strength and conditioning programs often integrate scapular stabilization and shoulder mobility work to optimize triceps performance and reduce the risk of compensatory injury.

Historical and comparative notes

• In humans and many other mammals, the triceps brachii is a defining extensor of the forearm. Across species, the relative development of the heads and the exact tendon arrangement reflect different locomotive and manipulation demands.

See also - olecranon - elbow joint - radial nerve - profunda brachii artery - scapula - humerus - infraglenoid tubercle - triceps tendon - accessory head of triceps brachii - Anatomy of the upper limb