Painful Arc

What is a Painful Arc?

Painful arc is a syndrome(1) that is characterized by severe pain in the shoulders; it’s is commonly known as Shoulder Impingement Syndrome.

Symptoms usually occur when the arms are raised overhead or above shoulder level, or when the arm is moved from sideways to the body. This shoulder pain results when repetitive injuries in the rotator cuff tendons cause inflammation in the muscles making the movements full of pain. Locating the exact site of lesions causing the painful arc is important to give the appropriate healthcare service.

Understanding the Anatomy

The Painful Arc occurs at the glenohumeral joint, i.e., the shoulder, and is the result of the vicious cycle that causes friction of the rotator cuff(2) which is present between the humerus and the top bone that lines the shoulder. There is a deltoid muscle area, the base of which connects with the clavicle and the scapula. The top outer edge of the shoulder has a blade which is called the acromion process. This blade rubs against and causes the rotator cuff tear.

A rotator cuff is a group of four muscles that line the shoulder which include the supraspinatus, infraspinatus, teres minor, and subscapularis. The muscles sit in the space between the bones called the subacromial space. These muscles originate on the shoulder blade and are inserted or attached to the rotator cuff. These rotator cuff muscles are basically responsible for helping you to move the arm above the forehead level and without any damage to the concerning bones. Moving your arm away and towards the body is also dependent on the rotator cuff present in between the two bones.

Causes of Painful Arc

Because of the closely positioned bones of the humerus, the shoulder blade (scapula), and the clavicle medial to the scapula, there is always a chance of rubbing and friction against each other causing the subacromial impingement syndrome. (3) Very similar reasons cause frozen shoulder (capsulitis) and arm dysfunction. This is how the patient becomes susceptible to this rotator cuff disease.

The causes of the damaged rotator cuff muscles include:

• The tendons and ligaments, specifically the coracoacromial ligament, involved are swollen or torn. This might happen because of a repetitive activity that includes the movement of these muscles and bones.
• Supraspinatus tendinopathy is also another condition that has very commonly been associated as a cause of shoulder impingement syndrome. Recurring stress and overuse of the supraspinatus tendon can cause its damage in middle age.
• The wear and tear of muscles can also be an age-related or an injury-related factor causing the flexion of the shoulder and arm pain.
• There is a fluid-filled sac between the tendons of the shoulder head and the acromion called the Bursa. This fluid-filled sac decreases the possible friction between the anterior edge of the bones, preventing the rotator cuff tears. If this fluid decreases or damage to the subacromial bursa sac occurs, the area can become inflamed.
• Bone spurs or naturally non-flat bone of the Acromion will result in painful arc syndrome.

People who Are Liable to Painful Arc

Those most susceptible to persistent impingement syndrome tend to be active(4) people who do regular gym for body shaping and health fitness without proper supervision. Activities that involve more rotational movements of the arm, like swimming, athletics, volleyball, basketball, baseball and tennis present greater risks of developing painful arc-induced shoulder pain.

Read next: Pain between the shoulder blades

Signs and Symptoms of Painful Arc

The signs and symptoms, like every other disease and syndrome, can vary slightly from patient to patient.

• Experiencing pain when extending it to reach something
• Experiencing pain when lifting the arm from a height or moving the arm above the head
• Experiencing pain and tenderness when the arm is at rest position
• Experiencing pain when reaching toward the back
• Pain that radiates from the shoulder front and reaches the arm side
• Difficulty lying or sleeping on the affected side of the body
• General arm weakness or stiffness

The symptoms related to impingement syndrome do not appear abruptly, but rather appear slowly over a period of weeks to months. Bursitis and Rotator cuff tendonitis are the common reasons for pain associated with this syndrome. While the pain can signify a tear in the muscles, it can also be a sign of shoulder injury. Proper clinical diagnostic tests are important to figure out the exact cause of the pain.

Chronic impingement syndrome

If the pain persists for a longer period of time and the acromioclavicular joint does not adjust itself in the space between the Bursa and the acromion, then there are chances of aggravated inflammation. This makes the condition progress rapidly, making it a Chronic Impingement syndrome. (5)

Diagnostic Tests for Painful Arc

Approximately, 44% to 65% of the people who present to the physicians with shoulder-related complaints are patients of painful arc syndrome. While figuring out the painful arc syndrome, the patient must be questioned for medical history, including the family history and the medication history. The diagnosis(6) can be done on the basis of radiological examination. It can also be done by physical examination and by considering the signs and symptoms.

Physical Examination

First of all, the symptoms would add up to indicate the impingement syndrome itself. Next, the physician will assess the range of motion the affected arm and shoulder will show. Physically pressing and checking the intensity and location of the pain is also important. The doctor will also inquire about the lifestyle of the patient and what type of activities is the patient involved in.

Radiological Examination

Last but not the least, the physician will recommend a radiological examination. X-ray is the older form of test prescribed. X-rays will only rule out the other possibilities of shoulder pain, such as arthritis, bone fractures, and acromioclavicular calcification. The image from the X-ray can also suggest an injury in the rotator cuffs. For the exact diagnosis of the pain, the physician will recommend an MRI (Magnetic Resonance Imaging). The soft tissue is visible because of its diagnosis accuracy. The method will clearly show the pathology of the muscles surrounding the rotator cuff but again obtaining several opinions before making a final diagnosis is recommended in this case.

Local Anaesthetic Injection

This is a reliable diagnostic test for the painful arc. The local anaesthetic lidocaine is utilized in this procedure with a suitable corticosteroid. The two drugs are mixed in a combination and injected into the fluid-filled sac of the Bursa. If the pain shows an improvement and the patient is able to move his shoulder joint and arm to a greater degree, then the test is considered positive and the results confirm that the patient suffers from Impingement Syndrome.

Painful Arc Test

If a patient has a painful arc sign, a basic test called an impingement test can also be conducted to confirm the presence of the syndrome. This is done by keeping the patient in a standing or sitting position. The patient is asked to quickly and actively lift up the arm in the direction of the scapular area and then reverse the position slowly back. Most probably, the patient would have difficulty doing the external rotation. If the patient experiences pain when the arm moves in between the angle of 60-120 degrees, then the test is considered positive for the impingement syndrome.

NEER Test

The doctor will hold the scapula of the affected side and straighten the patient’s arm. The patient will then be asked to flex the arm towards the internal rotation angle. Any pain reported during this movement confirms the NEER test.

Hawkins-Kennedy Test

This test is conducted by placing the patient’s arm shoulder at a right angle, and then bending the elbow in such a way that it makes 90 degrees again towards the inside. Now bend the wrist downwards and direct the patient to rotate the elbow arm towards the internal side. Any pain experienced during this movement gives a positive result to the impingement test.

Treatment of Shoulder Impingement Syndrome

There are a number of methods that can be employed to treat this pain syndrome. Some of them are as follows:

Physiotherapy

For initial stages where the pain is treatable by physical therapy, this is the most convenient form of therapy for most patients. It is more often recommended by your orthopaedic doctor who has already prescribed you medicines but would refer you to a physical therapist for further improvement. Physiotherapy requires just a few check-up calls at the physiotherapist clinic. He will instruct you on the proper movements for exercise. After that, the patient can practice the exercise himself or herself at home till the prescribed period.

Medications

There are a few medications(7) like corticosteroids along with pain killers that can be used to treat this condition. Initially, the patient has prescribed a Non-Steroidal Anti-inflammatory drug, like Ibuprofen or Naproxen. If the pain persists, stronger drugs like steroids are employed. A cortisone injection into the Bursa sac which is beneath the acromion bone.

Home Remedies

Some physicians also prescribe home remedies to patients who do not require vigorous treatment with surgery or steroid injections. These include the use of temperature changes on the affected side. Heating sources like a heat bag or ice for imparting cold temperature are both effective ways to reduce painful arc signs.

Surgery

If the non-surgical treatments do not decrease the pain and the patient shows no signs of comfort, surgery(8) remains the last option. Consulting an orthopaedic in this regard is the best step forward. The surgery is called subacromial decompression or arthroscopic shoulder decompression. The process involves the removal of parts of the bone that interfere with the free movement and causes irritation or inflammation. In this case, the acromion process is cut off from the top to prevent friction by small cuts in your shoulder. It depends on the surgeon, if he chooses to go for small incisions or open surgery.

Prolotherapy:

Many of the structures have a poor blood supply, which is why they can struggle to heal on their own. It is the oxygen and nutrients in our blood supply that help to heal these structures.

Prolotherapy involves the injection of a regenerative solution into these structures to provide a direct supply of what is required to heal and repair.

As the treatment is helping to treat the root cause of the problem, it is deemed to be a permanent fix.

Frequently Asked Questions

What does a Painful Arc indicate?

The painful arc itself is not a clinical condition but a sign indicative of an underlying problem. This may be most commonly experienced by individuals when their shoulder bursa or rotator cuff tendons become pinched under the acromion process. 

What is a Glenohumeral Painful Arc?

The painful glenohumeral arc is a sign associated with disturbances in the glenohumeral joint and its movement. This ball and socket joint allows articulation between the glenoid of the scapula and humerus. The range of motion which is associated with pain is between 6o to 120 degrees of outward elevation. 

What is a positive painful arc test?

The pain arc test is positive when the individual experiences pain while raising their scapula between 60 degrees and 12 degrees. This test is performed under the supervision of a health professional, who asks the patient to raise their arm in the scapular place. After this, they are asked to reverse the motion slowly.

How painful is impingement?

Individuals with impingement often report throbbing pain in their shoulder. This pain is also associated with stiffness and a reduced range of motion. When asked how they would describe this pain, the majority of the people compared it to a toothache. Some individuals may also experience swelling. 

How do you test for impingement syndrome?

To test for impingement syndrome, a majority of health professionals usually conduct the Kennedy impingement test of the shoulder. The patient is first asked to raise their arm so that their shoulders are at 90 degrees to the elbow. They are then asked to rotate the arm inwards. If the individual experiences pain during the internal rotation, the test is considered positive. 

How long can shoulder impingement last?

Shoulder impingement usually heals within three to six months. However, this is usually true for mild to moderate cases, while severe cases can take much longer. Therefore, it is recommended that the individual visits the doctor regularly to evaluate their progress.

References:

1. AlmekindersMD, L. C. (2001, July). IMPINGEMENT SYNDROME. Science Direct. https://www.sciencedirect.com/science/article/abs/pii/S0278591905702659
2. Yamamoto MD., A. (2010, January). Prevalence and risk factors of a rotator cuff tear in the general population. Science Direct. https://www.sciencedirect.com/science/article/abs/pii/S1058274609002043
3. Symonds, G. (1977, November 12). Painful shoulders and painful arcs. NCBI – NIH. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1632417/
4. Impingement syndrome in athletes. (1980, May 1). SagePub. https://journals.sagepub.com/doi/abs/10.1177/036354658000800302
5. Bone & Joint. (1985, November 1). Bone and Joint. https://online.boneandjoint.org.uk/action/cookieAbsent
6. Çalış, M. (2000, January 1). Diagnostic values of clinical diagnostic tests in subacromial impingement syndrome. Annals of the Rheumatic Diseases. https://ard.bmj.com/content/59/1/44.short
7. Non-Operative Treatment of Subacromial Impingement Syndrome* : JBJS. (1997, May). LWW. https://journals.lww.com/jbjsjournal/Abstract/1997/05000/Non_Operative_Treatment_of_Subacromial_Impingement.13.aspx
8. Dorrestijn MD, O. (2009). Conservative or surgical treatment for subacromial impingement syndrome? A systematic review. Science Direct. https://www.sciencedirect.com/science/article/abs/pii/S1058274609000718