Biceps Brachii

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Introduction

The biceps brachii (BB), commonly know as the biceps, is a large, thick muscle on the ventral portion of the upper arm.

The muscle is composed of a short head and a long head. The long head is located on the lateral side of the biceps brachii while the short head is located on the medial side.

The biceps brachii works across three joints, and is able to generate movements in glenohumeral, elbow and radio-ulnar joints.

Image 1: : Biceps brachii muscle. - Long head red, Short head green.

Origin and Insertion

The muscle is composed of a short head and a long head. 

1. The short head originates from the apex of the coracoid process of the scapula.
2. The long head originates from the supraglenoid tubercle of the scapula.

Both heads course distally and become a confluent muscle belly before tapering across the anterior aspect of the elbow, to insert on the radial tuberosity and the fascia of the forearm via the bicipital aponeurosis.

Approximately 30% of adults have some variation in the origin of the muscle. In many patients, a third head may arise from the humerus, but in about 2% to 5% of people, there may be supernumerary heads numbering anywhere from 3 to 7 in total.

Image 2: Biceps brachii of right side, attachments.

Nerve and Arterial Supply

Innervation of bicep brachii is by the musculocutaneous nerve C5, C6, C7.

Blood supplied by the muscular branches of brachial artery

Function

Despite what some think, the biceps is not the most powerful flexor of the forearm. Although the biceps is the most prominent muscle of the upper arm, it serves to support and stabilize the deeper (and stronger) brachialis muscle whenever lifting or lowering the forearm.

The main functions of the biceps are the flexion and supination (outward rotation) of the forearm. This is facilitated, in part, by the 90-degree rotation of the muscle as it connects to the radius.

The actions of the BB at its primary joint are well known. The BB is a flexor of the elbow, a powerful supinator of the forearm, and has a smaller role in shoulder flexion.

There are multiple actions across the elbow and shoulder joints with which the BB is involved, all in conjunction with other muscles. It is:

1. One of three muscles that flex the elbow and it does this work along with the brachialis and brachioradialis.
2. One of three that flex the shoulder (with coracobrachialis and anterior deltoid)
3. One of two that supinate the forearm (with supinator).

Of these motions, the elbow flexion and supination are well established. Its actions at the shoulder have been investigated through a variety of approaches although questions still remain. The BBLH is thought to enhance the dynamic stability of the shoulder joint, but only in the initial 30° of elevation.

The biceps brachii actions differently to movements to the upper limb dependant on joint positions:

• Extended elbow: Biceps is a pure elbow flexor until it reaches 90 degree flexion
• At 90 degrees flexion and forearm supinated: Most efficient to produce elbow flexion
• At 90 degrees flexion and forearm pronated: Biceps becomes the primary forearm supinator

Viewing The 7 minute video below goes into details on the Biceps Bracii

Physiotherapy

The biceps brachii is prone to repetitive micro-trauma due to stress or overuse. Sports involving throwing, eg baseball and cricket, badminton and tennis, are common to over-stress tendons of the biceps and causing inflammation. As a result, biceps tendinopathy of its long head or bicep tendon are common condition sees in the muscle.

• LHB tendinopathy occurs in association with RC pathology, Subacromial impingement syndrome, or in tandem with subscapularis injuries.
• In the setting of RC tears, 90% of cases demonstrated concomitant LHB tendinopathy, and 45% of cases had additional LHB instability.

More serious BB conditions, eg dislocation and rupture of tendon of the long head of biceps, are not uncommon across all age groups.

When rehabilitaing the BBLH remenber:

Beyond 30°, the BBLH, even though contracting, does not create a noteworthy elevation moment, suggesting that it cannot serve as a dynamic shoulder stabilizer in higher ranges of elevation.

• Exercises planned to rehabilitate the shoulder. should involve low level elevation, which can increase the BBLH dynamic role in stabilizing the joint when elevated to 30° or less.
• Incorporating eccentric contractions through the lower range of elevation would be appropriate since this could mimic the deceleration phase of the overhead throwing motion.

Assessment

Detailed history should be completed prior to physical examinations. A basic examination should include observation, palpation, muscle strength testing and range of motion. Obvious deformity, known as "Popeye sign", might be observed with rupture of long head tendon of the biceps.

• Palpation of the anterior aspect of the arm should include the full length of the muscle. Tenderness similar to patient's complaint might be reproduced via palpation. It is also useful to locate the site of injury.
• Muscle strength test of the biceps should be completed in supine of sitting with patient's arm well support by a cushion of a hand of the examiner. Patient's elbow positioned slightly less than or at right angle with forearm in supination. Examiner should then apply pressure against the lower forearm in the direction of extension. Weakness might present with patient symptoms.
• Examiner could observe the range of motion of the elbow using a goniometre. Examiner can also palpate and look for crepitus in the elbow joint.
  palpation
• Muscle length test: see video below

Treatment

see Biceps tendonopathy

See also

Rupture Long Head Biceps

Biceps Load II Test

Biceps Tendonitis

Yergasons Test