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The coracobrachialis muscle is a small, slender muscle located in the upper medial part of the arm, close to the armpit. It is involved in multiple actions, including bending the arm (flexion) and pulling the arm towards the trunk (adduction) at the shoulder joint. The muscle originates from the coracoid process of the scapula and inserts into the upper arm bone. The coracobrachialis muscle is not one of the most prominent arm muscles, and it does not play a significant role in moving the arm. However, it can become tight or strained from certain activities, potentially causing shoulder or arm pain.
| Characteristics | Values |
|---|---|
| Location | Front of the upper arm, close to the armpit |
| Appearance | Long, slender, strap-like |
| Function | Bending the arm, pulling the arm towards the body |
| Attachments | Shoulder joint, upper arm bone |
| Nerve | Musculocutaneous |
| Blood Supply | Branch of the brachial artery |
| Injury | Possible strain from overuse, e.g. pushups, gymnastics, heavy bags |
| Pain | Shoulder, arm, radiating to the back of the hand |
| Treatment | Rest, massage, trigger point therapy |
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What You'll Learn
The coracobrachialis muscle's origin, insertion, and innervation
The coracobrachialis muscle is a small, pencil-like muscle located in the upper arm. It originates from the coracoid process of the scapula, which is a small, hook-like structure that protrudes from the shoulder blade. From its origin at the coracoid process, the coracobrachialis muscle travels distally and inserts on the medial aspect of the humerus, which is the long bone of the upper arm. Specifically, it attaches to a ridge-like structure called the medial crest, which is located on the humeral shaft.
The function of the coracobrachialis muscle is to adduct the arm, moving it across the body toward the midline, and also to flex the arm, bringing it forward and upward. Additionally, this muscle plays a role in stabilizing the shoulder joint and maintaining the proper positioning of the humeral head within the glenohumeral joint.
The coracobrachialis muscle has an interesting and somewhat complex innervation. It is primarily supplied by the musculocutaneous nerve, which is a branch of the brachial plexus. The brachial plexus is a network of nerves that arise from the lower cervical and upper thoracic spinal cord segments, and it provides nerve supply to the upper limb. Specifically, the musculocutaneous nerve arises from the lateral cord of the brachial plexus, which is formed by the anterior divisions of the lower cervical nerves (C5-C7) and the first thoracic nerve (T1).
Additionally, there is an interesting anastomosis, or nerve connection, that involves the coracobrachialis muscle. The musculocutaneous nerve communicates with another nerve called the median nerve through a branch called the medial cutaneous nerve of the forearm. This communication provides a dual innervation to the coracobrachialis muscle, as the median nerve can also supply motor fibers to this muscle. The median nerve arises from the lateral and medial cords of the brachial plexus and typically provides sensation to the palm and motor control to some of the hand muscles.
In summary, the coracobrachialis muscle has a specific origin at the coracoid process of the scapula and inserts on the medial crest of the humerus. Its primary function is arm adduction and flexion, along with shoulder stabilization. The muscle is innervated by the musculocutaneous nerve, with a potential additional contribution from the median nerve due to an anastomosing branch. Understanding the anatomy and innervation of the coracobrachialis muscle is important for comprehending the neural pathways and muscle interactions in the upper limb.
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The muscle's function and relation to other muscles
The coracobrachialis muscle is a small, slender muscle located in the upper medial part of the arm, specifically in the anterior compartment of the arm. It is involved in bending the arm (flexion) and pulling the arm towards the trunk (adduction) at the shoulder joint. It is a weak flexor and adductor and is not considered a significant muscle in terms of arm movement.
The muscle originates from the coracoid process of the scapula and inserts into the middle of the medial aspect of the humerus. It is innervated by the musculocutaneous nerve, which can cause referred pain from the shoulder down the arm when irritated. The musculocutaneous nerve also supplies the biceps brachii and brachialis muscles. The coracobrachialis lies beneath the short head of the biceps brachii, and its tendon attaches to the medial side of the humerus, between the brachialis and the medial head of the triceps.
The coracobrachialis is classified into distinct superficial and deep layers, with some individuals having a full or partial separation of these layers. It is located medial to the biceps brachii and brachialis muscles and is crossed anteriorly by the median nerve. The muscle is also located posterior to the pectoralis major muscle and anterior to the tendons of the subscapularis, latissimus dorsi, teres major, and the medial head of the triceps.
The main actions of the coracobrachialis are flexion and adduction of the arm, and it acts as an antagonist to the deltoid muscle during arm abduction and extension. It also resists deviation of the arm from the frontal plane during abduction. Overuse of the coracobrachialis can lead to muscle hardening and pain in the arm, shoulder, and hand.
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How to identify and treat a strained coracobrachialis
The coracobrachialis is a small muscle located in the upper arm, near the armpit. It is responsible for flexion and adduction at the glenohumeral joint (shoulder joint). It is not one of the most prominent arm muscles, and it does not play a significant role in moving the arm. However, it can become strained through trauma, overuse, or over-training, leading to pain and stiffness.
Identifying a Strained Coracobrachialis
If you experience unexplained shoulder or arm pain, especially after activities that involve repetitive arm movements or heavy lifting, your coracobrachialis might be strained. To identify if the pain originates from this muscle, press on the muscle, which is located at the front and top of your upper arm, close to your armpit. If pressing on the muscle hurts or makes your pain worse, it is likely the source of your pain.
Treating a Strained Coracobrachialis
If you have strained your coracobrachialis, the best treatment is rest. If the muscle has become stiff and tight, massage or trigger point therapy might help. Trigger points can be released through pressure self-release techniques, followed by gentle stretching of the muscle.
For myofascial pain, trigger point therapy, also known as the Niel Asher Technique, can be beneficial. This involves working out the hard knot in the muscle to relieve pain. Additionally, postural corrections, stretching, and avoiding activities that overload the muscle can help prevent further strain.
If you are experiencing persistent or severe symptoms, consider visiting a sports medicine physician or a physical therapist for hands-on treatment.
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The muscle's location and structure
The coracobrachialis muscle is located in the upper medial part of the arm, specifically in the anterior or front compartment of the arm. It is a small, slender muscle that is not very prominent and is hidden beneath the short head of the biceps brachii. It can be felt most easily at the lateral border of the axilla or armpit.
The coracobrachialis originates from the coracoid process of the scapula, which is a bony projection on the shoulder blade that serves as the muscle's attachment site. From there, the muscle fibres run inferolaterally towards the humerus, inserting onto the anteromedial surface of the humeral shaft or upper arm bone. The insertion site is located about halfway down the upper arm, on the armpit side, between the brachialis muscle and the medial head of the triceps.
The coracobrachialis muscle is surrounded by several other muscles, including the pectoralis major, subscapularis, latissimus dorsi, teres major, and the medial head of the triceps. It is located medial to the biceps brachii and brachialis muscles, and its humeral insertion is crossed anteriorly by the median nerve. The coracobrachialis is also perforated by and innervated by the musculocutaneous nerve, a branch of the brachial artery and the lateral cord of the brachial plexus.
The structure of the coracobrachialis muscle has been classified into distinct superficial and deep layers. In most individuals, there is no discernible separation between these layers, but in some cases, there may be a complete or incomplete division. The muscle is a weak flexor and adductor of the arm at the glenohumeral joint (shoulder joint), and it also resists deviation of the arm from the frontal plane during abduction.
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Rupture of the coracobrachialis
The coracobrachialis is a small, slender muscle located at the front of the upper arm, close to the armpit. It is not one of the most prominent arm muscles and does not play a significant role in moving the arm. However, it can become tight from certain activities, leading to shoulder or arm pain.
One case study describes a 57-year-old female who suffered a proximal coracobrachialis tendon rupture from its origin at the coracoid process, along with a subscapularis tear and medial dislocation of the long head of the biceps tendon after a first-time traumatic anterior shoulder dislocation. Another case study involves a 19-year-old male right-arm cricket bowler who experienced a sudden jerk injury while bowling, resulting in a partial rupture of the coracobrachialis muscle with a large hematoma at the proximal myotendinous junction.
The coracobrachialis muscle functions as a flexor, adductor, and internal rotator of the shoulder, and it stabilizes the shoulder joint when the arm is at the side. It is important to be aware of the rare rupture of this muscle as it may be misdiagnosed as a distal biceps tendon rupture.
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Frequently asked questions
The coracobrachialis muscle is located in the upper medial part of the arm, within the anterior compartment of the arm.
The main actions of the coracobrachialis muscle are bending the arm (flexion) and pulling the arm towards the trunk (adduction) at the shoulder joint. It also resists deviation of the arm from the frontal plane during abduction.
Overuse of the coracobrachialis muscle can lead to stiffening and hardening of the muscle. Common causes include bench pressing with heavy weights, carrying heavy loads with hanging arms, and gymnastics.
If you've strained your coracobrachialis muscle, the recommended treatment is rest. If the muscle has become stiff and tight, massage may help.
