Shoulder Impingement Syndrome
What is shoulder impingement syndrome?
Shoulder impingement occurs when the top outer edge of your shoulder blade, called the acromion, rubs against (“impinges on”) or pinches your rotator cuff beneath it, causing pain and irritation.
What is my rotator cuff and what does it do?
As seen in the illustration, your rotator cuff is a group of four muscles that originates on the shoulder blade and attaches as a “cuff’ of tendon onto your arm bone (humerus).
You use your rotator cuff to help raise your arm overhead and to rotate your arm towards and away from your body. You will notice in the illustration that the rotator cuff sits in a small space between two bones in the shoulder (the acromion and the humerus). This arrangement makes the rotator cuff susceptible to being pinched or “impinged” between these bones, leading to what is called “impingement syndrome.”
Rotator cuff is a group of muscles that sits in the small space between the acromion and the humerus.
How does shoulder impingement syndrome develop?
When your rotator cuff is irritated or injured, it swells in much the same way your ankle does when it is sprained. However, because your rotator cuff is surrounded by bone, swelling causes other events to occur. Swelling reduces the amount of space around the rotator cuff, leading to rubbing against the acromion. Like a vicious cycle, the rubbing of the rotator cuff tendons result in swelling, which further narrows the space below the acromion. In some cases, bone spurs on the acromion bone can contribute to impingement by causing the space where the rotator cuff sits to be even more narrowed
Who gets shoulder impingement?
Shoulder impingement syndrome is most commonly seen in individuals who are involved in sports and other activities with a lot of overhead rotational motion – like swimming, baseball, volleyball and tennis as well as things such as window washing and painting.
Shoulder impingement can also result from an injury, such as a fall onto an outstretched arm or directly onto the shoulder.
How common is shoulder impingement?
Shoulder impingement syndrome is thought to be the cause of 44% to 65% of all shoulder pain complaints.
Symptoms and Causes
What causes shoulder impingement?
Your rotator cuff tendon passes through a space below the acromion. The acromion is the bony tip of the outer edge of your shoulder blade (scapula) that comes off the top of the back side of this bone. It meets with the end of your collar bone (clavicle) at your shoulder. Shoulder impingement occurs when the tendon rubs against the acromion.
The causes of this impingement include:
- Your tendon is torn or swollen. This can be due to overuse from repetitive activity of the shoulder, injury or from age-related wear and tear.
- Your bursa is irritated and inflamed. Your bursa is the fluid-filled sac between your tendon and the acromion. Your bursa helps your muscles and tendons glide over your bones. Your bursa can become inflamed due to overuse of the shoulder or injury.
- Your acromion is not flat (you were born this way) or you have developed age-related bone spurs on your acromion.
What are the symptoms of shoulder impingement syndrome?
Symptoms of shoulder impingement syndrome include:
- Pain when your arms are extended above your head.
- Pain when lifting your arm, lowering your arm from a raised position or when reaching.
- Pain and tenderness in the front of your shoulder.
- Pain that moves from the front of your shoulder to the side of your arm.
- Pain when lying on the affected side.
- Pain or achiness at night, which affects your ability to sleep.
- Pain when reaching behind your back, like reaching into a back pocket or zipping up a zipper.
- Shoulder and/or arm weakness and stiffness.
Symptoms usually develop gradually over weeks to months.
Shoulder impingement is closely related to other common sources of pain in the shoulder called bursitis and rotator cuff tendonitis. These conditions can occur alone or in combination. Shoulder pain can also be a sign of a more serious injury to your rotator cuff, a small tear or hole called a rotator cuff tear. If your rotator cuff has torn completely, you’ll likely have significant weakness and may not be able to raise your arm against gravity. In addition, you may have a rupture (tear) of your biceps muscle tendon as part of this continuing impingement process.
Diagnosis and Tests
How is shoulder impingement syndrome diagnosed?
Your healthcare provider will take your medical history and perform a physical examination to check for pain and tenderness. Your provider will also assess the range of motion of your shoulder and your arm/shoulder strength. They will ask if you are involved in repetitive activities that require overhead arm movement, what remedies you have tried to relieve your pain, prior injuries to the affected arm/shoulder and any details about what may have caused your shoulder pain and when it began.
X-rays are helpful to rule out arthritis and may show the rotator cuff injury. There may be bone spurs or changes in the normal outline of the bone where the rotator cuff normally attaches. Magnetic resonance imaging (MRI ) and ultrasound can show tears in the rotator cuff tendons and inflammation in the bursa.
A diagnosis of impingement syndrome may be made if a small amount of an anesthetic (painkiller), injected into the space under the acromion, relieves your pain.
Management and Treatment
How is shoulder impingement syndrome treated?
The goal of treatment for shoulder impingement syndrome is to reduce your pain and restore shoulder function. Treatments for impingement syndrome include rest, ice, over-the-counter anti-inflammatory medications, steroid injections and physical therapy.
- Physical therapy is the most important treatment for shoulder impingement syndrome. In most cases, you’ll only need one or two in-office visits to learn how to continue to do physical therapy on your own at home. You’ll learn stretching exercises to improve the range of motion of your shoulder. As your pain lessens, you can begin strengthening exercises to improve your rotator cuff muscles.
- Ice should be applied to the shoulder for 20 minutes once or twice a day. (A bag of frozen peas or corn also works well).
- If your healthcare provider approves, ibuprofen or naproxen may be taken as-needed to relieve pain. For more severe pain, a stronger prescription strength anti-inflammatory medication may be prescribe or a cortisone injection into the bursa beneath the acromion may be given.
- A common sense approach to activities is helpful. Avoid activities in which you need to frequently reach overhead or behind your back. These motions usually makes shoulders with impingement syndrome worse. Stop activities that involve these motions until your pain improves.
Surgery is considered if nonsurgical treatments don’t relieve your pain. One surgery called a subacromial decompression or arthroscopic shoulder decompression removes part of the acromion to create more space for the rotator cuff. This procedure can be performed arthroscopically, which means through small cuts (incisions) in your shoulder. Other problems with your shoulder can be repaired at the time of surgery including arthritis in the shoulder, inflammation of the biceps tendon and partial rotator cuff tear. Open surgery, a surgery with a larger cut in the front of your shoulder, is another option.
Outlook / Prognosis
What outcome (prognosis) can be expected if I have shoulder impingement?
If you follow your treatment plan of rest, ice, anti-inflammatory medications, physical therapy and cortisone injections, your shoulder may improvement in a few weeks or months. About 60% of people who follow these conservative therapies report satisfactory results within two years.
If your pain does not improve with nonsurgical treatments, surgery may be recommended.