Impingement Syndrome


Many commonly used terms such as impingement syndrome, rotator cuff tendinosis, rotator cuff tendinitis, subacromial bursitis and bone spur can be broadly classified under the “umbrella term” of impingement syndrome. As such, these conditions will all be discussed in this article.

Shoulder pain is a common complaint that many patients present with and impingement syndrome accounts for between 40 – 60% of these patients. “Impingement syndrome” is a non-specific diagnosis which was coined to cover the range of rotator cuff disorders, back in the days when sophisticated and accurate investigations were not available.

The term “impingement syndrome” was used because it was recognised that many problems with the rotator cuff could not be reliably differentiated on physical examination. In this article, I will not be discussing rotator cuff tears because that is a huge topic and will be discussed separately.

In order to understand this problem, some basic knowledge of the anatomy of the shoulder as well as the tendon structure of the is required.

Anatomy of the Shoulder Joint

The shoulder joint is made up of 3 bones: the shoulder blade (scapula), the humeral head and the collar-bone (clavicle).

Movements around the shoulder involve 3 separate articulations: the glenohumeral joint, the acromioclavicular joint and the scapulothoracic articulation. When the arm is raised, the majority of movement occur at the glenohumeral joint and the scapulothoracic articulation.

Four (4) muscles are attached to the scapula and send their respective tendons across the glenohumeral joint and attach to the humerus just beyond the humeral head. These 4 tendons are collectively known as the rotator cuff. You can think of the muscles as motors and their tendons as pulleys. Contractions of the muscles will hence bring about movement at the joint that their tendons cross.

Many patients do not know the difference between tendons and ligaments. Though structurally similar, the 2 structures have very different roles. Tendons arise from the end of muscles, cross a joint and attach to a bone beyond the joint.

Contractions of the muscles then bring about movements at the joint. Ligaments, on the other hand, connect 2 bones across a joint. They keep the joint together and prevents the joint from falling apart (dislocating).

A part of the scapula, known as the acromion, forms a roof over the humeral head and rotator cuff (see picture of bony anatomy of the shoulder). To reduce friction between the acromion and the underlying rotator cuff during shoulder movements, a thin sac containing a sliver of fluid sits on the superior surface of the rotator cuff. This sac is known as the bursa

What symptoms might I experience?

The most common symptom that patients experience is pain. The pain is typically felt just beyond the shoulder, underneath the deltoid muscle. Any attempt to lift the arm to the sides of the body while keeping the elbow straight (a movement known as abduction) will cause a sharp pain.

This pain is sharp in nature and often occurs during a characteristic arc of movement between 60° and 120° (the painful arc).

Occasionally, patients may describe a sudden loss of power as a result of this sharp pain, which may result in them dropping loads while trying to hoist them overhead. I often hear patients mention that they are either unable to lift their luggage onto the overhead cabins of planes or have even dropped their luggage as a result, and further injured their shoulders!

The pain is often also aggravated by forced overhead movements. There is usually little to no pain at rest, but lying on the affected side often exacerbates the pain. This is especially bothersome to side sleepers.

Some patients may feel that their affected side is weaker than the unaffected side and this may be more noticeable if the affected side happens to be their master arm.

Many patients experience these symptoms after having suffered an injury to the shoulder. The mechanism of injury may vary widely from falls to motor vehicular accidents to “spraining” their shoulders while attempting to carry a heavy load.

In my daily practice, patients often tell me they injured their shoulder during sports but they did not think much of it, since the pain was very mild initially.  The pain, however either persisted and in some cases worsened prompting them to seek help.

In the local context, many patients come only after having tried and failed traditional treatment modalities like massages, herbal medications, acupuncture, cupping, moxibustion etc.

What will the doctor do?

Your doctor will chat with you and ask you more about the. A careful examination of the shoulder is then carried out. He (I will use “he” to refer to the doctor to simplify the discussion although clearly, there are many female doctors out there!) will need to visually inspect your shoulders, looking out for any asymmetry or wasting of the muscles.

He then feels around the shoulder looking for any tender spots which may give a clue as to the source of the problem. This may be particularly hard in large or muscular patients.

He then tests your shoulder movements. Typically, in RC tendinosis or impingement, shoulder range of movement is not significantly affected. Patients may encounter pain raising their arms but if they are able to put up with the discomfort, they usually are able to fully raise their arms.

Your doctor will then test the strength in each of the RC muscles. The most commonly affected tendon is the supraspinatus tendon and many patients with RC tendinosis will have decreased power in the supraspinatus due to pain.

Finally, he will usually carry out a couple of clinical tests designed to elicit discomfort, in an effort to clinch the diagnosis.

The 3 most common tests are:

1. Impingement sign: The arm is internally rotated while at the side of the body. The arm is then raised from the front, while keeping the arm fully internally rotated. Pain is elicited at the top of the movement.

2. Hawkins Test: The shoulder is held at the front of the body with the elbow flexed at 90°. The arm is then internally rotated. Pain is elicited if rotator cuff tendinosis is present

3. Jobes Test: The arms are held straight, raised 30° to the side of the body and brought forwards 30°, while fully internally rotated. Downward pressure is then applied to the arms while the patient actively resists the downward pressure. This causes either pain or weakness is detected by the doctor.

Your doctor should have a couple of suspicions as to what is ailing your shoulders at this point in time. He will often need to carry out some investigations to confirm his suspicions.

What tests can be done to confirm the diagnosis?

This section will briefly discuss the common investigations that doctors carry out to identify the problem. For a more detailed discussion regarding investigations, please go to the page on investigations.

Many doctors may begin their investigations with x-rays for the shoulder. X-rays are excellent investigations for viewing bony and joint problems.

To me, x-rays provide me with a “bird’s eye view” of the problem. X-rays, however are not terribly informative in cases of RC tendinosis or impingement. It used to be thought that the shape of the acromion seen on the y-scapular view (or outlet view) of a shoulder x-ray was responsible for impingement.

Three (3) types of acromions were described: flat, curved and hooked. It was postulated that a hooked acromion resulted in impingement by abrading the RC. This theory, though, has been debunked in many studies.

Ultrasound scans are generally more useful in the diagnosis of RC tendinosis and impingement syndrome than x-rays. In the hands of an experienced ultrasonographer, it is possible to differentiate between the common RC issues.

Concomitant intra-articular pathology, however, may be missed because they are obscured by the bony anatomy. Lastly, in the event that a bad rotator cuff tear is detected, ultrasound examinations may not yield enough information for the surgeon to assess the chances of a re-tear of the tendon even after successful surgical repair.

An MRI (magnetic resonance imaging) scan is by far, the most informative scan, and it is my investigation of choice for RC problems. It gives excellent information regarding intra-articular structures like the cartilage and labrum. At the same time, it also yields excellent information with regards to the rotator cuff, presence of any tears of the RC tendons, state of the RC muscles etc.

I am told I have impingement syndrome. What does that mean?

As mentioned above, “impingement syndrome” does not refer to a single disorder. It refers to the signs and symptoms that patients with bursitis; rotator cuff tendinosis; partial tears of the rotator cuff and full thickness tears of the rotator cuff, may encounter.

Many doctors still use the term “impingement syndrome”. There are many reasons for this. Probably one of the biggest reasons is that this term has been in existence for over 40 years.

Generations of doctors have been taught the concept of impingement and it is hard to change mindsets that have been so deeply ingrained. Personally, I avoid using this term because I prefer to be more specific with the diagnosis.

This allows me to explain the problem to my patients with greater accuracy. It also allows me to tailor the treatment to the individual patient, rather than apply a “one-size-fits-all” kind of approach.

Having said that, some treatment modalities (like physiotherapy and pain medications) can be applied to all the issues as a whole, but must be modified and tailored to each condition.

I am told I have tendinosis of my rotator cuff. What is that?

Tendinosis of the rotator cuff means “wear and tear’ of the rotator cuff tendon. The most commonly affected tendon (out of the 4 rotator cuff tendons) is the one that sits on top of the humeral head called the supraspinatus tendon.

Many patients are taken aback when I say “wear and tear” because they associate it with aging. But I often see tendinosis in patients in their early twenties! It is arguably the most common disorder I see in patients with “impingement syndrome”.

Is tendinosis and tendinitis the same thing?

No, they are different. Let us look at the structure of a tendon in greater detail. A tendon is composed of an outer sheath which houses longitudinally arranged strands of collagen.

The collagen strands are then packed in increasingly larger bundles, bound together by protein and eventually form the final tendon.

Tendon cells (called tenocytes) are found distributed within the structure of the tendon. Their function is to produce more collagen and protein required for repairing the tiny damage that occurs in daily life.

Blood vessels travel between the bundles, bringing blood and nutrients to supply the tenocytes.

Many tendon disorders were previously thought to be secondary to inflammation. When a tendon is injured, the body launches an inflammatory response. Cells at the site of injury secrete chemical substances that result in proliferation and dilation of blood vessels.

In addition, these blood vessels also become more “leaky”, allowing proteins and fluid within the blood stream to leak out into the surrounding tissues. This results in swelling, redness, increased warmth and pain.

However, many researchers have found that typical inflammatory microscopic findings in patients with rotator cuff issues are puzzlingly absent. Instead, what they found was that the neat structure of a healthy tendon was lost and replaced by a disorganized tenocytes and collagen, with interspersed holes filled with mucoid substances, distorted and dead tenocytes, inappropriate deposition of calcium and microtears of the tendon structure.

As such, the term tendinosis is now being used to more accurately describe this disorder. Certainly, inflammation still occurs, but is usually seen in acute injuries in previously healthy tendons. In those cases, it would be accurate to describe the condition as tendinitis.

I'm told I have bursitis as well. What is bursitis?

The bursa is usually a very thin membraneous sac that sits between the overlying acromion and the underlying rotator cuff tendon. As we raise our arms, the area where the rotator cuff attaches rolls under the acromion.

The bursa helps to reduce the amount of rubbing that occurs between rotator cuff and the acromion. If there is excessive chafing, the bursa starts to become injured and irritated. Inflammation follows, resulting in swelling of the bursa and eventually, thickening of the walls of the bursa.

This in turn causes pain with arm movements at the shoulder, particularly with overhead movements.

There's a bone spur as well! What is that?

It is actually extremely common to see all these problems in a patient with shoulder pain. The bone spur refers to a sharp spike that is seen on the undersurface of some acromions. You may even hear doctors talking about whether you have a curved or a hooked acromion.

Most shoulder surgeons these days do not attach much importance on these terms anymore. The simplistic understanding previously was that the presence of a sharp bone spur physically grinds on the underlying rotator cuff and eventually tears the latter.

This theory has largely been debunked. The bone spur is often hidden within a ligament that sits in front of the acromion and does not physically contact the rotator cuff in most cases.

Having said that, on occasion, I do see bone spurs that arise from the acromion where it joins the clavicle (the acromioclavicular joint) and sometimes, these bone spurs do indeed appear to be indenting the underlying rotator cuff.

So while a bone spur abrading the rotator cuff is not as common as often described, it is not impossible or “fake news” and may occur in some patients!

How can impingement syndrome be treated?

‍In almost all cases of impingement syndrome, I generally start patients off with non-invasive treatment modalities first. If non-invasive options prove to be ineffective, I then move on to more invasive options.

The first thing to do is to modify one’s activities. The patient should avoid any activities that aggravate the pain. This may include taking a break from his/ her sport, avoiding carrying heavy loads, avoiding overhead lifting etc.

Due to the slow rate of repair of tendons, a period of rest of at least two to three weeks may be required.

Prolonged, complete rest, however may be counter-productive. Mechanical loading of the tendon has been shown to increase metabolism of tenocytes, hence this may stimulate the tendon to heal faster. As such, some judicious loading of the tendon, after a short period of rest, is prudent. This is where physiotherapy comes in.

What non-invasive treatment options are there?

Physiotherapy is a common modality of treatment for the various conditions included under the umbrella of impingement syndrome. It can, however a somewhat “soft science”. Many physiotherapists have different philosophies and approaches.

Eccentric loading of the injured tendon has been found to be effective in treatment of tendon disorders. Many physiotherapists will incorporate various treatment modalities into their treatment, including ultrasound, radiofrequency, shockwave, deep tissue massages, various stretching and strengthening exercises etc.

Medications are used mainly for alleviating pain. The two groups of medications used are painkillers (eg paracetamol, codeine, opiates etc) and anti-inflammatory medications (aspirin group of drugs).

Medications are generally not used as a “cure” for the condition, but rather to make the condition more bearable for the patient.

If a reasonable period of time has elapsed and the patient’s condition has not improved with non-invasive treatment options, invasive treatment options will have to be considered.

What kind of invasive treatment options are there?

Invasive options comprise injections and surgery.

Cortisone (steroid) injections are commonly given especially in cases where no rotator cuff tear has been identified on scans. Steroids suppress inflammation and are used in inflammatory conditions such as tendinitis and bursitis.

Steroids should not be injected directly into the rotator cuff tendon tissue, as this causes cell death and tendon atrophy, but they are often injected into the bursa that overlies the tendon. As steroids are anti-inflammatory, they result in reduced inflammation, hence reducing pain.

In recent years, however, the role of steroid injections has been increasingly controversial.

Since tendinosis has been shown to be a non-inflammatory process, the rationale for using steroids has been called into question. Worse, steroids have been shown to inhibit collagen synthesis so it might result in hindering tendon healing.

I generally avoid the use of steroids in patients with proven rotator cuff tears, and only use them in patients whose scans show inflammatory changes in the bursa. Anecdotally in carefully selected patients, steroid injections have been rather effective in bringing about pain relief.

It is my practice, also, to limit steroid injections to just a single injection. Should the pain recur, I would not administer another steroid injection.

Plate rich plasma (PRP) injections have also been used in impingement syndrome. The theory behind PRP is simple. Your blood contains many chemicals that your body produces to bring about healing. A small amount of blood is taken from you and spun down in a centrifuge. The blood separates into a lower intense red layer and clear top layer.

The clear layer is collected and injected into the area where healing is desired. Because this layer is rich in chemicals required for healing, theoretically, healing should occur more readily wherever it is injected.

As always, clinical practice is not as straightforward. Clinical studies have not convincingly shown that PRP injections work. So although PRP’s efficacy is questionable, it is at least a rather safe treatment modality with few minute risks.

As such, while I do not routinely prescribe PRP in the treatment of impingement syndrome, if the patient requests for it and is very keen on giving it a go, I would still accede to their requests.  

Surgery is another somewhat controversial topic in impingement syndrome. In the past, it routinely involved removing the bursa and shaving off the bone spur.

This was based on the theory that the bone spur physically abrades the rotator cuff tissue resulting in inflammation and eventually, tears of the rotator cuff. As this theory has been conclusively debunked, the rationale of shaving off the bone spur has also been questioned. Many recent studies have not shown any benefit of shaving off the bone spur.

As such, this is not a surgery I routinely do for impingement syndrome, unless the patient’s scans convincingly show indentation of the rotator cuff by an unusually large bone spur.

All of the surgeries I perform for impingement syndrome are via minimally invasive techniques (keyhole surgery). I have found that in some patients with persistent pain from impingement syndrome and bursitis, surgical removal of the inflamed bursa does result in effective long-term pain relief.

Some surgeons add on procedures aimed at stimulating tendon healing. These may include making shallow cuts on the surface of the rotator cuff, or making small holes in the rotator cuff using a radiofrequency probe.

None of these procedures have been proven to be of any benefit, hence I do not perform any of them. For a more detailed description of shoulder surgery, please refer to the page on Keyhole Surgery.

For patients in whom a tear of the rotator cuff has been identified on scans, the decision-making process is a lot easier. As rotator cuff tears are a huge topic on their own, they will be discussed separately (please refer to the page on Rotator Cuff Tears).

What should I do now?

If you have managed to get to this part of this long article, your shoulder must be bothering you significantly! Consult your family doctor or see an orthopaedic specialist and he/she should be able to advise you accordingly.

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