The shoulder is a complex upper-body structure that connects the arms to the torso. It is made up of a number of parts that work together to offer stability and a wide range of motion.
The shoulder is a huge and complicated ball-and-socket joint with several bones, muscles, tendons, and ligaments. These structures work together to construct and support this very flexible joint, which allows the arms to move freely. However, because of this mobility, the shoulder can be damaged by overuse, instability, or injury.
The anatomy, function, and structures of the shoulder will be discussed in this article.
Because of the variety of structures that make up the shoulder, it is a complex part of the body that can move freely. The shoulder includes the body’s most mobile joint, allowing for a high range of motion but at the sacrifice of stability. It’s prone to getting hurt.
Three primary bones meet at the shoulder to form a 90-degree angle. The pectoral girdle is made up of two of these bones: the clavicle and scapula. The collarbone and shoulder blade are the common names for these bones. The humerus, which is the biggest bone in the arm, is the third bone.
The glenohumeral, acromioclavicular, and sternoclavicular joints are formed by the intersection of these bones and the sternum, or chest bone. The great range of motion of the shoulder is due to these joints.
The joints are subsequently surrounded by cartilage, ligaments, muscles, and tendons, which unite the bones and provide stability. Muscles also enable movement.
The primary purpose of the shoulder is to offer a wide range of motion for the arms. People who can raise, lower, and rotate their arms can accomplish a variety of actions, including tossing and reaching, as well as athletic movements like swimming.
The shoulder’s bones and joints
The shoulder is made up of three bones. These are the following:
- The clavicle: This bone, also called the collarbone, connects the arm to the chest and is located in front of the scapula. It is connected to the arm, the neck, and the chest through a number of muscles.
- The scapula: The shoulder blade is also known as the scapula. It’s triangular in shape. It primarily adheres to the body through muscle and “floats” off the rear of the chest. The acromion, a bony component of the scapula, connects it to the clavicle. On the scapula, the glenoid is a shallow socket.
- The humerus: The humerus is the bone in the upper arm. Between the elbow and the shoulder is a lengthy bone called the humerus. At the top of the arm, the humerus bears a spherical part that acts as a “ball” for the scapula’s “socket.”
The shoulder is made up of three joints. These are some of them:
- The glenohumeral joint: A ball-and-socket joint is what this joint is. It is the joint that links the humerus to the scapula. It is the body’s most movable joint. The shoulder can move in various planes, including arm rotation and moving the arm up and away from the body, thanks to the joint.
- The acromioclavicular joint: The clavicle is joined to the scapula by this. The clavicle joins to the scapula by a bone component known as the acromion. The shoulder is stabilized by this joint, which also aids movement such as elevating the shoulders.
- The sternoclavicular joint: The clavicle is connected to the sternum by this. The sternum is the flat bone in the center of the chest, often known as the breastbone. The clavicles can move thanks to the joint.
Muscles of the shoulder
Extrinsic and intrinsic muscles make up the shoulder. Extrinsic muscles come from the torso and attach to the shoulder’s bones, whereas intrinsic muscles come from the scapula or clavicle and attach to the humerus.
The following muscles make up the intrinsic muscles of the shoulder:
- The deltoid: The deltoid is a triangular-shaped muscle on the outside of the shoulder. It connects the clavicle to the scapula. The deltoid muscle permits you to move your arm forwards, backwards, sideways, and away from your body. It also helps to keep the shoulder stable while carrying and lifting.
- Teres major: The scapula gives rise to this muscle, which joins to the humerus. Internal rotation of the arm is possible because to Teres major.
- Supraspinatus: This muscle originates from the scapula and attaches to the humerus. It helps to support the glenohumeral joint and allows the arm to move out from the body.
- Infraspinatus: The scapula gives rise to this muscle, which joins to the humerus. It turns the arm externally and stabilizes the glenohumeral joint.
- Teres minor: The teres minor stems from the scapula and connects to the humerus. It rotates the arm laterally while also stabilizing the glenohumeral joint.
- Subscapularis: The scapula gives rise to this muscle, which joins to the humerus. It permits the arm to rotate towards the body while also stabilizing the glenohumeral joint.
The rotator cuff muscles are the supraspinatus, infraspinatus, teres minor, and subscapularis muscles. All of them come from the scapula and connect to the humerus. These muscles work together to raise and rotate the arm.
The following muscles make up the extrinsic muscles of the shoulder:
- The trapezius: The trapezius is a muscle that runs from the base of the head to the clavicle and scapula. The scapula is raised.
- Latissimus dorsi: The humerus bone is attached to this muscle, which originates in the lower spine. It assists with pull-ups and rowing exercises by bringing the arm backwards and towards the torso.
- Levator scapulae: This is a long, narrow muscle that aids in scapula elevation. It also aids in glenoid cavity rotation, spine stabilization, and neck extension and lateral flexion.
- Rhomboid major and rhomboid minor: The rhomboid muscles help rotate the glenoid cavity by stabilizing the scapula and maintaining it in place.
While the shoulder is incredibly mobile, its suppleness leaves it vulnerable to injury and instability. These injuries can limit your range of motion and cause shoulder pain. The following are some of the most prevalent shoulder ailments:
Rotator cuff injuries
Trauma to any of the muscles and tendons that make up the rotator cuff is referred to as a rotator cuff injury. The following are some of the most common rotator cuff issues:
- Tears: When a tendon is torn, it no longer fully adheres to the bone, which is a common injury. Injury and age-related deterioration are the most common causes of rotator cuff tears. While treatment varies depending on the severity of the condition, it usually include rest, pain medication, and rehabilitation activities. Surgery may be required in more severe situations.
- Bursitis: The bursa, which are fluid-filled sacs that cushion and protect tissues by decreasing friction, is inflamed. The bursa can be irritated and inflamed by infections or too much friction from repetitive movements or injuries. Antibiotics, rest, corticosteroid injections, and surgery may be used as treatment options in more severe cases.
- Tendinitis: This is an inflammation of the tendons that might cause it difficult to lift the arms. It usually happens as a result of tendons irritation or damage caused by sports or repetitive overhead movements. It’s also known as a shoulder impingement by certain people. Rest, physical therapy, and injections are common treatments, but if these don’t work, surgery may be required.
Arthritis is a condition in which the joints become inflamed. The cartilage in people with arthritis is destroyed, and the joint no longer has a smooth surface.
Arthritis can cause pain, decreased range of motion, and a clicking sounds in the shoulder joints, especially the acromioclavicular and glenohumeral joints.
The following are examples of arthritis that can affect the shoulder:
- rheumatoid arthritis
- avascular necrosis
- rotator cuff tear arthropathy
- post-traumatic arthritis
Treatment will vary depending on the type and severity of the arthritis, but it will usually start with nonsurgical options including rest, physical therapy, and pain relievers. When these methods fail or the pain becomes incapacitating, a doctor may recommend surgery.
Broken bones are also known as fractures. As a result, a shoulder fracture develops when the scapula, clavicle, or head of the humerus breaks. Fractures can occur as a result of:
- car accidents
Shoulder fractures can often be treated without surgery by a doctor. This usually entails wearing a sling to immobilize the shoulder and allowing it to heal. However, if the bone is entirely out of place, surgery may be required. This usually entails placing plates, screws, or rods inside the bone to stabilize the fracture.
When the humerus comes partially or completely out of the glenoid, it is referred to as a shoulder dislocation. The shoulder is the most often displaced joint due to its mobility, with forward, or anterior, dislocations accounting for roughly 97 percent of all occurrences.
A doctor will most likely conduct a closed reduction to repair a shoulder dislocation. This is a process in which the humerus is reinserted into the joint socket. After that, a doctor may recommend resting or immobilizing the shoulder before beginning rehabilitation exercises once the pain and swelling have subsided.
A dislocation can sometimes be so severe that it necessitates surgery. If the shoulder becomes unstable following a dislocation, surgery may be required to prevent recurrent dislocations.
Shoulder health advice
The following steps can be taken to ensure that a person’s shoulder is healthy and has a decent range of motion:
- before exercising, make sure you extend your shoulder muscles properly
- when working or playing sports, avoid overusing the shoulder muscles
- using an exercise program to strengthen the shoulder muscles
- shoulder pain should not be ignored, and if the pain persists, a doctor should be consulted
- attempting to stay away from activities that could result in a fall or accident
The shoulder is a complex structure with numerous bones, muscles, and tendons. These components come together to form a movable joint that allows the arms to move freely.
The shoulder, however, is prone to instability and injury since it is a mobile joint that many people utilize regularly. Rotator cuff injuries, shoulder arthritis, fractures, and dislocations can all cause pain and interfere with shoulder function. Treatment, rest, stretching, and exercising as soon as possible might assist to strengthen the shoulder and speed up healing.