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Why Is My Shoulder Aching ?
There is a big list of causes for Shoulder pain. Few of these causes are not originating from the shoulder joint itself, known as; Referred pain. The causes of Shoulder pain might differ from one person to another according to gender, age, lifestyle, occupation and general medical condition. Before we discuss this list, we would like to enumerate few facts about the Shoulder joint. 1- It is composed of an articulation between the Humerus Head and the Glenoid ( part of the Scapula ). 2- It has the biggest range of motion of any joint in the body. 3- It is the most commonly dislocated joint, with anterior dislocation being the most common.
Causes Of Shoulder Pain
1- Shoulder Arthritis
A prevalent cause of shoulder pain, especially in older people. Age is just a number, but in general, by 50–60 years, arthritis becomes a common cause of joints pain ( Shoulder, hip, knee, etc.). Arthritis can be idiopathic ( no cause ) or secondary to systemic disease, trauma, etc. Discriminator: Usually, the pain increases with activity and decreases with rest unless the arthritis is advanced, leading to the ongoing constant pain.2- Rotator Cuff Diseases
Rotator cuff pathology is common among younger and older patients. A spectrum of diseases affect the Rotator cuff as; impingement, inflammation, partial or full tears. Discriminator: With impingement or small tears, the pain is usually at the extreme range of motion as the muscles impinge on the bony structures. In big tears, the pain could be constant and associated with much decrease in range of motion, plus night pain could occur.3- The Long Head Of The Biceps Muscle
The biceps muscle has two heads; long and short ones. The long head is intra-articular, meaning it runs in the joint. This long head can get inflamed ( synovitic ) or even get torn; it will cause anterior shoulder pain and upper arm pain in both cases. Discriminator: Pain is usually located in the anterior aspect of the shoulder, just distal to the joint ( on the upper arm ).4- Labral Injuries
The labrum is the soft tissue lining around the glenoid. It helps to provide stability by increasing the depth of the glenoid ( socket ). Labral injuries can be acute or chronic. Chronic injuries ( also known as degenerative ) can cause deep shoulder pain with range of motion. Acute injuries are more common in younger patients; this could be due to a single traumatic event or ongoing repetitive load to the joint. Discriminator: Deep joint pain which could be associated with clicking, especially in cases of acute injuries in younger patients or could be associated with the sensation of instability in acute cases secondary to dislocation ( in this case, it might be a painless sensation of instability with an almost full range of motion ). In older patients with chronic degenerative labral injuries, the pain is mild and similar to arthritic pain.5- Acromioclavicular Joint Arthritis
The acromioclavicular joint is a small joint with very little motion located anteriorly and on top of the main shoulder joint ( Glenohumeral joint ). This articulation is between the Acromion ( part of the scapula/shoulder blade ) and the Clavicle ( collar bone ). This joint might get arthritic ( narrowing of the space ), causing pain very well localized anteriorly yet can be perceived as shoulder pain. Discriminator: Localised point of pain/tenderness over the joint on the anterior aspect of the shoulder region. This is usually not associated with decreased range of motion nor night pain if it occurs in isolation.6- Nerve Pain
Few nerves run around the shoulder as; Axillary, Suprascapular, and Infrascapular nerves. Impingement of any of these nerves around the shoulder would cause pain ( usually sharp shooting pain ). Discriminator: Sharp shooting pain ( rather than aching pain ), referred down to the arm.7- Brachial Plexus Injury
The brachial plexus is the bundle of nerve trunks and cords arising from the neck and feeding the whole upper extremity down to the fingertips. Brachial plexus injuries due to systemic diseases or secondary to trauma will cause shoulder pain. Discriminator: As in nerve pain, sharp shooting pain with weakness in the muscles involved and decreased sensation in the affected dermatomes in the arm/forearm/wrist and hand.8- Neck Pain
Also called referred pain since the pathology is not originating from the Shoulder joint itself. This is a prevalent cause of pain that could be thought of as shoulder pain, yet the shoulder is non-pathologic, yet it just perceives the pain. Neck pathologies as degenerative disc disease, spinal stenosis, foraminal stenosis ( foramen where the nerve root exits the spinal cord ) or paraspinal muscle spasm can cause neck and shoulder pain. This pain can be associated with numbness, tingling and maybe weakness down to the hand level, which is very uncommon in true shoulder pain when the pathology originates from the joint. Discriminator: Pain in the neck and/or the paracervical muscles that might be increased with neck range of movements, plus pain/numbness and tingling radiating down the arm.9- Infection
This is uncommon without predisposing factors as shoulder surgery, open fracture or underlying immunocompromised disease, yet it can also occur spontaneously. This can be presenting as cellulitis or shoulder joint infection. It is usually associated with redness, swelling, decreased shoulder range of motion, fever etc. Discriminator: Constant aching pain even at rest associated with skin redness, swelling, and systemic changes as fever and chills.10- Inflammation
For example; Bursitis ( which is different from the infection since there is no pathogen). It is inflammation of the tissue either inside the shoulder joint or in subacromial space or extra-articular. The intra-articular usually presents as the rotator cuff pathology, while the extra-articular could present with redness and swelling. Discriminator: Like rotator cuff pathology, the superficial bursae can present with redness and swelling plus focal localized pain.11- Frozen Shoulder ( also known as Stiff Shoulder )
It can occur without any reason but is more commonly present after shoulder surgery, more in females, diabetics, breast cancer treatment, cardiovascular diseases, myocardial dysfunction, thyroid dysfunction, and sedentary life. Discriminator: Decreased range of motion usually starts with external rotation deficiency, and pain increases with the range of motion. The passive range of motion will be equally affected as well.12- Scapular Pain
This can be due to few reasons as trauma or dyskinesia ( altered scapular position and motion ). Dyskinesia can be due to; Kyphosis, clavicular fracture malunion or nonunion, or scapular winging. Discriminator: Usually, there is either history of trauma or deformity on physical examination13- Trauma
This could lead to fractures ( proximal humerus fracture, scapular fracture, Acromioclavicular joint separation etc.), dislocations or soft tissue injury. If treatment of any of these was ignored or mismanaged, this might lead to Shoulder pain. Discriminator: History of trauma, if you had a fall or accident, you should be checked by a medical doctor (i.e. don’t ignore your first injury, occasionally we see injuries weeks or months after the initial incident, which sometimes lead to suboptimal outcomes).14- Muscular
The muscles around the shoulder can get fatigued over time. This can be due to ageing or ongoing abnormal posture. A common disease in this category is called; Upper Cross Syndrome, where the neck, upper back, shoulder, or chest muscles become deformed and acquire different non-anatomic positions leading to a change in the dynamics and eventually ongoing pain. Discriminator: This usually occurs in people who sustain certain positions for long hours as; sitting on a desk in the wrong way for a long time, biking, driving etc.15- Systemic Disease
A big list of diseases that can lead to joint pain as; Inflammatory Arthritis, Fibromyalgia, Multiple Sclerosis, etc. ( the list goes on ). Even cardiac conditions as a heart attack can present with left shoulder pain. Discriminator: History of systemic disease ( If you have a known medical condition, you can review its clinical picture and talk with your doctor ).
Very interesting topic. Thank you.