Subacromial impingement refers to pain that people experience at the front and top of their shoulder when reaching up. It makes it difficult to perform usual daily activities such as washing your hair and reaching into high shelves. It can also affect your sleep because many people cannot lie on the affected side. You may have also heard this condition called subacromial bursitis.
The short answer is anyone! Most patients are over 40 years old. It usually comes on by itself, but some people recall a trivial injury that sets it off.
For many people, it can be caused by a small spike of bone that grows down from the outer end of the shoulder blade. This is referred to as an acromial spur. As you bring your arm up, your tendon can become trapped between that spike of bone and your humerus (arm bone), causing pain. Sometimes, a minor injury can set off some inflammation on the outside of your tendon, causing a similar problem with pain coming on as you raise your arm.
There are many other causes of impingement-like pain. Some people can develop a weakness or imbalance of their shoulder muscles. This may prevent their shoulder joint from moving properly and result in impingement pain. This is one reason why physiotherapy is very important in the treatment of subacromial impingement. Some people have a torn rotator cuff tendon in their shoulder. This leads to abnormal shoulder movement and can cause impingement pain. It is therefore important for your doctor to examine you carefully and sometimes arrange for an ultrasound or MRI scan to check whether or not you have a tear.
Finally, other conditions can cause the same type of pain. One example is calcific tendonitis, which is a build-up of calcium inside the tendon. This causes the tendon to swell and rub between the two bones, causing pain. Occasionally, the calcium can burst out of the tendon, causing a sudden and severe worsening of the pain. Click here to see my latest video about the causes of impingement pain.
This starts with a conversation with your doctor to describe when you experience the pain. You will then be examined, with some specialised tests that help to distinguish impingement from other causes of shoulder pain and to check for torn tendons. Often, your doctor will request an X-ray to look for an acromial spur or deposit of calcium. If your doctor suspects a rotator cuff tear, they may arrange for an ultrasound or MRI scan.
For some people, just knowing what the problem is, and having the reassurance that there is no major damage to the shoulder is enough. The pain can be controlled with simple painkillers, such as paracetamol and anti-inflammatories (if you can take them). This may be coupled with simple changes to your lifestyle, such as sleeping on the opposite side or putting heavy items on lower shelves at home.
A course of physiotherapy is very effective for subacromial impingement. Your physiotherapist will assess your movements and teach you ways of moving your shoulder without experiencing the pain. If you have an imbalance in the muscle strength around your shoulder, this will also be addressed. It can take several months to get the full benefit of physiotherapy, so it is important to work hard early on, even if you do not feel an immediate benefit.
You may be offered a steroid injection into your shoulder. This is sometimes referred to as a cortisone injection. The purpose of this injection is to settle down any inflammation in your shoulder. This is a very effective treatment, especially when coupled with physiotherapy. By taking the pain away, even temporarily, it can make it easier to do the exercises given to you by your physiotherapist. There are several rare risks of steroid injections:
If the above treatments are not successful, surgery may be helpful to treat subacromial impingement. This is usually performed 'keyhole' and is often referred to as an arthroscopic subacromial decompression.