Shoulder Ligaments vs. Joint Capsule The shoulder joint capsule is a band of connective tissues that encompasses the head of the humerus.

It helps to hold the humerus in the glenoid ( socket ) when the shoulder is at rest. While many of us think about these tissues connecting our skeletal matter, the joint capsule plays a crucial role in this function as well.

Not like the knee, which has ligaments that are individual bands of tissue, the deltoid has thickenings in places of the joint capsule that are referred to as ligaments. Let me explain…

The shoulder ligaments aren’t seperate from the joint capsule. In reality, they are not really ligaments at all, in the way you suspect about ligaments like the ACL or PCL in the knee. They’re simply areas of tissue that are thicker than the other portions of the capsule. So, your physician may refer to the shoulder ligaments as a part of the capsule, or as ligaments, but they mean a similar thing.

The Glenohumeral Shoulder Ligaments: The shoulder has three different areas of thickening in the capsule, which can be referred to as ligaments. These are the anterior glenohumeral ligament, inferior glenohumeral ligament, and posterior glenohumeral ligament. The ligaments provide stability to the joint, and help to restict disproportionate joint motion. Notice in the picture the way in which the inferior ligament ( or capsule ) appears to hang down from the humerus. This is significant as we discuss shoulder function.

Anterior Shoulder Ligaments Anterior Glenohumeral Ligament – sporting injury Data The anterior shoulder capsule helps to prohibit forward motion of the humerus. It also helps to limit external revolution. As will all ligaments and joint capsules, the shoulder ligaments all become tight with different motions. The anterior capsule becomes tight when the shoulder is flexed above ninety degrees, or when it is externally revolved. The anterior glenohumeral ligament is the tissue that’s wounded with 95% of all shoulder dislocations.

When the shoulder dislocates, it always comes forward and down. This stretches and tears the anterior part of the joint capsule, and the anterior glenohumeral ligament. The commonest position for shoulder dislocation is when the arm is out to the side, above shoulder level, and the elbow bent to ninety degrees. In this position, the anterior capsule and ligament is tight…forced motion in this position will noticeably stress the capsule, and may cause damage.

Inferior Shoulder Ligaments Inferior Glenohumeral Ligament – sporting injury Information The inferior glenohumeral ligament is a redundency of the shoulder capsule. In the picture you can see how it hangs down from the humerus…almost like there’s too much tissue there. This is not the case. You see, when the shoulder moves, the capsule must be in a position to stretch and evolve.

If the inferior capsule wasn’t hanging down, you would not be ready to raise your arm over your head. When the arm is raised above shoulder level, the inferior capsule starts to tighten. The inferior capsule isn’t often wounded during sports…however, it can become unacceptably tight if the arm is immobilized for a long-lasting period. Ever heard about frozen shoulder? This is the part of the capsule that frequently tightens down and causes frozen shoulder.

Posterior Shoulder Ligaments Posterior Glenohumeral Shoulder Ligament – sporting injury Information .

The posterior shoulder ligament, aids in keeping too much rotation on the inside of the deltoid muscle. It can develop problems from becoming overly compressed, however, it’s not usually prone to the more blunt type of sports injuries. As an example, baseball pitchers many times get a tightening of this structure due to their profession. This can then lead to various impingement problems.

Overal the shoulder ligament has a crucial position in the body to provide stability and performance. Both by moving via flexion and also by a stopping mechanism to avoid overexertion and pain.

* Anterior fibers : from the anterior border and higher surface of the lateral clavicle.

* Middle fibers : from the lateral margin and higher surface of the acromion

* Posterior fibers : from the lower lip of the posterior border of the backbone of the scapula, as far back as the triangular surface at its medial end.

Insertion: From this in depth origin the fibers come together toward their insertion, the middle passing vertically, the anterior obliquely backward and laterally, the posterior obliquely forward and laterally ; they unite in a thick tendon, which is inserted into the V-shaped deltoid tuberosity on the middle of the lateral side of the shaft of the humerus. At its insertion the shoulder muscle releases an enlargement to the deep fascia of the arm.

Innervation: The deltoid is innervated by the axillary nerve. The axillary nerve originates from the ventral rami of the C5 and C7 spinal nerves, thru the superior trunk, posterior division of the superior trunk, and the posterior twine of the brachial plexus. The axillary nerve is often damaged during operations on the axilla , for example for breast cancer. It might also be hurt by unacceptable use of crutches.

Action: When all of the shoulder muscles fibers contract at the same time, the deltoid is the prime mover of the arm along the frontal plane. The arm must be internally revolved for the deltoid to have maximum effect. This makes the deltoid an antagonist muscle of the pectoralis major and latissimus dorsi during arm adduction. The anterior fibers are concerned in shoulder movement when the shoulder is outwardly revolved. The anterior deltoid is feeble in stern cross flexion but helps the pectoralis major during shoulder cross flexion / shoulder flexion ( elbow a touch not so good as shoulders ). The posterior fibers are strongly concerned in cross extension especially since the latissimus dorsi is terribly feeble in stern transverse extension. The posterior deltoid is also the first shoulder hyperextensor. The lateral fibers are concerned in shoulder kidnapping when the shoulder is internally revolved, are concerned in shoulder flexion when the shoulder is internally rotated, and are concerned in shoulder cross kidnapping ( shoulder outwardly revolved ) — but aren’t made use of seriously during stern cross extension ( shoulder internally revolved ).

A very important function of the shoulder muscle in humans is stopping : preventing the dislocation of the humeral head when a person carries heavy loads. It also guarantees an accurate and quick movement of the glenohumeral joint required for hand and arm manipulation. The deltoid is in charge of raising the arm in the scapular plane and its contraction in doing this also raises the humeral head.

To stop this squeezing against the undersurface of the acromion the humeral head and wounding the supraspinatus tendon, there’s a concurrent contraction of the muscles of the shoulder muscles.

Despite this there could be still a thirteen mm upward movement of the head of the humerus in the first 30 to sixty of arm elevation.

Evolution: The deltoid is in other apes. The human deltoid has an analogous proportional size to that of the muscles of the rotatory cuff to apes such as orangutans that engage in brachiation in which it holds the arm when used to the postpone the body. However in common chimpanzees the deltoid is much enlarged weighing 383.3g compared to the human one of 191.9.

Despite this it is of less proportional mass to the shoulder muscles of the chimpanzees. This reflects the requirement in a knuckle walking ape to strength the shoulder usually especially the rotatory cuff so it can support body weight. The Deltoid is a classical example of a multipennate muscle. The middle fibres of the muscle arise in a bipenniform demeanour ( like a bird’s feather ) from the in number, which pass upward from the insertion of the muscle and swap with the descending septa. The portions of the muscle stemming from the clavicle and backbone of the scapula aren’t prepared in this demeanour, but are inserted into the margins of the inferior tendon.

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