Of all the muscle groups in your body, your shoulders are the most likely to get injured. Partly because of its mobility, and also because of its anatomy. Since the shoulder is an interconnected system of bones, muscles, ligaments, and tendons, whenever one structure is injured, the rest of the shoulder is compromised.
In this article, you will learn about the shoulder’s anatomy, the different types of shoulder injuries, how to diagnose them, and the courses of treatment available for each one.
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First, here’s a brief overview of the shoulder’s anatomy. For a more in depth look at each structure, you can check out this blog posthere.
Understanding the anatomy of your shoulders is important so you can properly diagnose and treat your shoulder injuries.
Thescapula, or commonly known as the shoulder blade, is prominently seen from your back. This bone supports most of the shoulder motion and acts as the base of the shoulder.
Theclavicle or collarbone connects your arm to your chest.
Thehumerus, or the arm bone, is the long bone that runs from the shoulder to the elbow.
The shoulder complex has four main joints: the glenohumeral, sternoclavicular, scapulothoracic, and acromioclavicular joints.
Theglenohumeral joint,commonly referred to as the shoulder joint, is a ball and socket joint that allows a wide range of movement. It is also considered as the most mobile joint of the body.
Thesternoclavicular joint is a type of saddle joint which connects the inner part of the collarbone to the breastbone. It allows movements shrugging back and forth motion.
Thescapulothoracic joint connects the scapula and the rib cage. It supports the arms when you perform push-ups and pull-ups.
Theacromioclavicular joint connects the outer part of the clavicle to the projection at the top of the shoulder blade called the acromion process.
Your ligaments are soft tissue structures that connect bones. Think of them as strong ropes that help connect bones and provide stability to joints.
The glenohumeral ligaments are the primary source of stability for the shoulders. They prevent the shoulders from dislocating by helping secure it in place.
The coracoacromial ligament connects the shoulder blade to the acromion and the coracoid process. It is responsible for maintaining the alignment of the clavicle. Calcification, or the accumulation of calcium salts, of the coracoacromial ligament, causes impingement syndrome.
The coracohumeral ligament strengthens the upper part of the shoulder joint capsule.
The coracoclavicular ligament connects the clavicle to the scapula's coracoid process. It keeps the acromioclavicular joint stable.
Your shoulders' muscles are responsible for movement and maintaining posture. Three main muscles make up the shoulders: Deltoid, Biceps, and the Rotator Cuff.
When people refer to the shoulders, they would most likely refer to their deltoids. The deltoid is also known as the common shoulder muscle and is composed of three segments: the anterior, lateral, and posterior fibers.
The deltoid muscles allow you to rotate your arm inwards, reach forward and backward.
The anterior deltoid is located at - as the name suggests - the front portion of your shoulder, and is attached to the collarbone. The primary function of the anterior deltoid is for flexing the arm at the shoulder joint, rotating the shoulder inward, or raising your arms sideways.
The lateral or acromial deltoid is responsible for necessary shoulder abduction. Shoulder abduction is any motion of the shoulder joint that involves lifting your arm away from the body.
The posterior deltoid's purpose is to extend the shoulder, like when you bring your arms behind you.
The biceps is a bi-articular, double-headed muscle on the front part of the upper arm. It is responsible for the motion of two different joints: the shoulder and the elbow. The short head begins at the coracoid process, and the long head starts at the shoulder joint. Both of these heads meet at the elbow.
Your rotator cuff is a group of muscles and tendons that surround the shoulder joint. It keeps the head of the upper arm bone securely attached to the shoulder socket. The rotator cuff is responsible for most arm movements, from raising to the rotation of the arm. It is the most commonly injured part of the shoulder, which usually manifests as a dull ache.
Your rotator cuff is a group of muscles composed of the following:
Thesupraspinatus muscle holds the humerus in place and is the muscle responsible for lifting your arm and giving it the support to keep it elevated.
Theinfraspinatus muscle assists in the rotation and extension of the shoulders.
Thetres minor muscle assists shoulder abduction.
Thesubscapularis is the muscle responsible for holding the arms straight out and keeping it elevated. It also supports the upper arm with the shoulder blade.
Aside from the deltoids, biceps, and rotator cuff, three muscles also help stabilize the scapula. These are the rhomboid, trapezius, and the serratus anterior muscles.
The rhomboid muscle is located in the upper back and helps to connect the shoulder blades to the ribs and the spine. The rhomboid muscles are responsible for maintaining good posture.
The trapezius muscleis composed of 3 muscle segments: the upper, middle, and lower trapezius. It is commonly called as "traps," and is responsible for motions like shrugging and pulling the shoulders back.
The serratus anterior muscle lies deep beneath the scapula and the pecs or pectoral muscles. This muscle is responsible for the forward rotation of the arm.
Learn more about the anatomy of the shoulders here.
Strains and Sprains
Shoulder strains and sprains occur when the shoulders are overstretched or torn. Sprains and strains may sound alike, but the difference between a shoulder strain and a sprain is in the location of the damage. A strain is a stretch or tear in the muscle and tendons, while a sprain is a stretch or tear in the ligaments.
Overstretching your shoulders can be caused by lifting objects which are heavier than you’re able to, or overworking your shoulders in sports. Tears, on the other hand, happen when your arms are forced backwards or when your shoulders are directly hit - like falling from a step ladder or hitting your shoulders against a pole.
What are the signs to watch out for?
A fracture is any damage to the shoulder's main bones - clavicle, scapula, and humerus.
Are you suspecting a fracture? Here are a few signs to watch out for:
Dislocations and Instability
The shoulder joint is the most frequently injured joint of the body. Aside from the fact that it's the most mobile joint, the humerus (long arm) is also longer than its socket (glenoid cavity), which makes it structurally unstable.
There are two types of shoulder dislocations: subluxation and complete dislocation.
Partial dislocation orsubluxation is when the shoulder joint partially slides out of place. On the other hand,complete shoulder dislocation is when the joint is entirely out of place.
Partial dislocations are more common, while it takes high-impact circumstances, such as extreme rotation of the shoulders or a terrible accident, to completely dislocate your shoulders. Whether they’re partial or complete dislocations, seek treatment as soon as possible since these could lead to more serious conditions.
The tricky thing about dislocations is that once you’ve experienced one, your shoulders become more susceptible to another. When dislocations occur frequently, it can lead to what we call shoulder instability.
Shoulder instability occurs when the structures that surround the shoulder joint lose their integrity and as a result, lose their ability to secure the ball within its socket.
Signs to watch out for:
Pain caused by shoulder impingement is persistent and annoying. It happens when tendons or the bursae, which are fluid-filled sacs near the joint, are impinged by the bones.
Overhead activities and sports such as baseball, tennis, volleyball are usual culprits to shoulder impingement. When not treated immediately, this may lead to a more advanced condition like bursitis.
Signs to watch out for:
Rotator Cuff Tears
The rotator cuff tendons cover the head of the humerus or the upper arm bone. They are responsible for securing the ball of the upper arm bone into the shallow socket of the shoulder, as well as arm movement.
Since they’re highly mobile, the rotator cuff can tear partially or completely - in which case the tendon becomes completely separated from the bone.
Rotator cuff injuries are degenerative injuries, which means they’re most likely caused by overuse.
Signs to watch out for:
When left untreated, rotator cuff tears can progress into rotator cuff arthropathy, which is shoulder arthritis, paired with a rotator cuff tear.
When the rotator cuff degenerates, the arm bone is unprotected from rubbing with the socket, resulting in pain and weakness.
Signs to watch out for:
Bursitis is the inflammation of the bursae. The bursae are fluid-filled sacs that cushion the bones, tendons, and muscles near the joints. They basically allow the rotator cuff tendons to glide freely.
When the rotator cuff tendons are injured or damaged, this bursa can also become inflamed and painful.
Signs to watch out for:
Frozen shoulder is the common name for adhesive capsulitis, which is a shoulder condition that limits your range of motion. When the tissues in your shoulder joint become thicker and tighter, scar tissue develops over time. As a result, your shoulder joint doesn't have enough space to rotate properly.
Muscle fatigue is a condition characterized by a feeling of weakness or tiredness in your muscles. Essentially, muscle fatigue is a state of exhaustion of your rotator cuff.
It might feel like your muscles are gradually becoming weaker and weaker or you may notice a significant decrease in flexibility or capability to carry heavy objects.
Symptoms of muscle fatigue:
Muscle strains are often caused by overworking or overstretching. Lifting heavy objects can stretch your rotator cuff beyond its capacity, and exhausting your shoulders in overhead sports can cause an injury.
Symptoms ofmuscle strain:
Rotator cuff tears can be grouped into 4 categories: partial, acute, chronic, and degenerative.
Partial tears are when the muscles or tendons are partially torn. Partial tears can develop from abrupt and intense movements such as heavy lifting, or it can be caused by a sudden impact such as falling on your shoulders.
Acute tears on the other hand are tears where the muscles or tendons are completely torn.
Chronic tears are usually seen in athletes (baseball, basketball) or lifters - a lot of overhead athletes.
These excessive overhead activities overwork the rotator cuff muscles on a continuous basis, thus making these tears chronic. Chronic injuries may also be because of a previous injury which had permanently affected the shoulder’s anatomy and functions.
Chronic tears may lead to a degenerative tear, eventually worsening your condition and decreasing shoulder mobility and function.
Degenerative tears do not come around on their own. They’re usually caused by succeeding shoulder injuries, or an acute injury that has permanently affected the shoulder anatomy.
Repetitive stress is a huge factor in acquiring degenerative tears, but another factor is age. Ageing affects the blood supply in the rotator cuff. When blood supply is lessened, recovery becomes difficult as the body’s ability to repair itself is compromised.
Bone overgrowth or bone spurs is also another condition that can happen when you don’t attend to your rotator cuff injuries promptly. Bone spurs develop on the underside of the acromion process. This in turn, rubs against the rotator cuff tendon and causes shoulder impingement. Individuals over 40 years old are highly at risk for this.
Rotator cuff arthropathy is a rotator cuff tear with shoulder arthritis. It is an advanced form of shoulder arthritis, where the shoulder loses not just the cartilage that covers the joint surface, but also the tendons of the rotator cuff which keep it in place. This makes shoulder movement painful since the upper surface of the bones are unprotected when they are rubbed against the ligaments.
You might have heard of tendonitis (inflammation of the tendon), which we’ll discuss later on, but have you heard of tendinopathy? These two are often interchanged, butsome studies have shown that tendinopathy actually causes tendonitis.
Tendinopathy is the breakdown of collagen in the tendon. Your tendons are fibrous structures which provide support to your muscles and connect muscles to bones. They are made up of collagen protein - a structural kind of protein that makes up ⅓ of all your body’s proteins. They’re a big deal.
Once this collagen protein breaks down, the integrity of your tendon structures are compromised, thus leading to tendon tears and inflammation.
Tendonitis is an inflammation of the tendons. While tendonitis can be caused by abrupt motions which in turn damage the tendon (such as falling or overstretching), most cases of tendonitis are caused by repetitive, strenuous activities such as overhead sports or job-related errands (painting, lifting, etc.)
Tendonitis can be easily addressed by conservative treatments such as using ice and compression, or taking non-steroidal anti-inflammatory drugs (NSAIDs.) Tendonitis left unattended can lead to more serious conditions like calcific tendinitis or frozen shoulders.
Calcific Tendinitis occurs when calcium deposits develop within the tendon.99% of your body’s calcium is in your teeth and bones, while the other 1% is in your blood. A bit of calcium build up is nothing to worry about, as it is your body’s response to injury, infection, or inflammation. However, chronic inflammation triggers calcium deposits to develop over a longer period of time. This is when it becomes a problem since calcium deposits harden and obstruct your tendons’ functions.
Frozen Shoulder is characterized, as the name suggests, by a stiffness in the shoulders. It can be caused by a lot of things including an advanced condition of calcific tendinitis. Someone who has a frozen shoulder often experiences constant pain which intensifies during the colder season and at night.
Shoulder SLAP Tears
Type I SLAP tear manifests as a frayed or torn labrum. This type is common among middle-aged or senior patients and is caused by the wear and tear of the labrum.
Type II SLAP tear manifests as a tear (or full detachment) to the biceps anchor. This type is a common result of high impact injuries.
Type III tear manifests as an extensively frayed labrum that forms a bucket handle tear, with an extension into the bicep tendon.
Type IV SLAP tear is the most severe type as it is a combination of a bucket handle tear paired with a bicep tendon tear.
Shoulder arthritis is the wearing out of the cartilage surrounding your glenohumeral joint.(Need a quick refresher on your shoulder’s anatomy? Here’s a comprehensive guide for your reference.)
The glenohumeral joint, commonly referred to as the shoulder joint, is the ball and socket joint that connects your humerus and glenoid cavity. It allows you to swing your arms forward and back, basically giving you your full range of motion.
Shoulder arthritis affects the cartilage or the living tissue that serves as a surface cover for your humerus.
Rotator cuff tear arthropathy is a severe and complex form of arthritis. It is a hybrid of two painful conditions: a shoulder arthritis and a largerotator cuff tear.
Rotator cuff tear arthropathy is a chronic condition and rarely needs medical attention. However, should you experience any of the following, see your physician immediately:
When not addressed immediately, rotator cuff tear arthropathy can lead to the progressive destruction of the humerus (arm bone) and the glenoid activity.
Arthritis due to Avascular Necrosis
Avascular Necrosis is otherwise known as osteonecrosis (aseptic necrosis or ischemic bone necrosis), which is the death of bone cells.
It might seem irrelevant to arthritis since it is a disease resulting in the death of bone cells. However, if it affects the bones near the shoulder joint, it can lead to the collapse of the shoulder joint surface, resulting in arthritis.
Causes of avascular necrosis:
The treatment for avascular necrosis operates in the same way as that for arthritis. The treatment focuses on managing symptoms as well as preserving the shoulder bone and preventing further bone loss.
The RICE Method is the most common way to address minor shoulder pain and injuries.
Remember that icing is only for first aid treatment or used in conjunction with painkillers, or your doctor's advice. If pain persists, consult your doctor immediately.
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