Shoulder osteoarthritis

How does shoulder osteoarthritis develop?

At the beginning, the joint cartilage, which is the sliding layer of the joint partners, is overloaded, it swells and becomes softer. This makes it more susceptible to injury, but also less resistant to stress. If the strain continues unabated, the surface of the cartilage can become roughened. Osteoarthritis takes its course. This is because the two joint partners no longer slide smoothly, which can lead to small cracks in the cartilage. The joint reacts to this with inflammation, which can damage the cartilage even more. The joint produces an effusion and causes pain. The cartilage layer becomes thinner and is completely worn away in the most stressed areas. The pain increases and mobility in the joint decreases. In order to reduce the pressure points in the joint, the body tries to enlarge the joint surface - it creates osteophytes. However, these also impair mobility in the joint. Osteoarthritis is now at an advanced stage.

As always with osteoarthritis, there are many possible causes. A distinction is made between internal and external factors:

Internal factors

These include genetic disposition, which is partly responsible for the strength and resistance of the cartilage. However, there are also diseases that affect the cartilage, such as chronic inflammation in rheumatism. In addition, the growth phase and diet determine the cartilage layer and its structure.

External factors

Rotator cuff

If the rotator cuff is damaged, especially if its tendons on the humeral head are torn, the humeral head is no longer guided correctly in the joint. The increased joint play can lead to excessive wear and tear. In addition, the humeral head becomes decentred over time. This leads to an asymmetrical load in the joint, which can wear down the socket on one side. This is referred to as cuff tear arthropathy. If the upper tendon of the rotator cuff is torn and retracted, the humeral head may rise up in the joint and chronically rest against the acromion. This is painful and causes the joint anatomy to change. It aligns itself with the hip - acetabulisation takes place.

Dislocation (instability)

Osteoarthritis can occur particularly in the shoulder due to dislocation. If the humeral head is pulled out of the joint, its cartilage rubs against the front edge of the socket. This is quite sharp-edged and can therefore damage the cartilage on its own. Occasionally, dislocation of the shoulder can even lead to a (small) fracture of the bone at the humeral head (Hill-Sachs lesion). However, the glenoid cavity can also be affected, as very strong forces are exerted during dislocation. The joint lip can be torn off (Bankart lesion). And the asymmetrical pressure alone can damage the cartilage on both sides.

Overloading

Another cause of osteoarthritis can be overloading, e.g. during sport or at work. Overloading can affect both the rotator cuff and the joint directly. As mentioned, the strain affects the cartilage surface. And if the load is greater than the ability to regenerate, wear and tear can occur.

Accident

Accidents, especially bone fractures, not only affect the bone, but almost always the neighbouring joints as well. Depending on how a force is applied to the body or arm, it is transferred to the joint before the bone fracture - the cartilage is damaged. However, there are also fractures that go through the joint and then form a step or a trench. These often require surgery to restore the joint as well as possible. This does not always work perfectly. It is particularly difficult to treat such fractures on the humeral head. The consequences of inadequate treatment can be devastating.

Infection

Joint infections are particularly feared by orthopaedic surgeons. If a bacterium manages to penetrate the joint, it can lodge and hide in the cartilage, which has no defence of its own. By the time symptoms appear, the bacterium has had time to multiply. And because the joint space is not supplied with blood, but with synovial fluid, it is very difficult for antibiotics to reach it. This is why such infections are often very difficult to treat, and all too often surgery is needed to clean the joint - sometimes even several times in succession. In most cases, the cartilage is severely damaged and joint replacement with a prosthesis is imminent.

What symptoms does shoulder osteoarthritis cause?

First and foremost: osteoarthritis hurts; not to the same extent for everyone, but the main symptom is pain. Typically, it is shooting pain during movement, especially during exertion. It is often not possible to localise it exactly, it is somewhere in the shoulder. Occasionally the pain also radiates to the neck or arm.

With advanced osteoarthritis, this is sometimes accompanied by pain at rest. This feels like a dull burning sensation, a slight inflammation and is always present. Many patients also complain of pain at night and it is often no longer possible to lie on the affected side. Because the affected arm moves less, the shoulder blade has to work harder. As a result, its muscles become overloaded and begin to ache. This tension typically often moves into the neck. This becomes stiff and can cause severe back pain, sometimes even headaches. It is not uncommon for patients to feel their neck and back more than their shoulder.

Restricted mobility

In most cases, the mobility of the arm is no longer as it should be quite early on. Movements over the head or onto the back are difficult or very painful. Even putting on a jacket can become a major exercise. Later on, lifting the arm is generally more difficult. This is not only a problem when getting dressed. Combing and even eating can also become difficult. Personal hygiene is also made more difficult.

Crepitations

Cracking or crunching in the shoulder can be quite normal; a little fluid sloshing around or the acromioclavicular joint cracking when the arm is raised. This is nothing out of the ordinary as long as it doesn't hurt. But with osteoarthritis, cracking often occurs in conjunction with pain. This is a sign that the cartilage no longer glides smoothly, but runs bumpily.

Swelling/redness

Because the shoulder joint is thickly surrounded by muscles, swelling is very rarely noticed. However, it contributes to the restriction of mobility. If you can no longer move your arm well, the blood in it no longer circulates well and the arm can also swell. Reddening is also hardly ever seen on the shoulder because the skin is not directly on the joint. The large muscle sheath shields the redness.

Bursitis

Whenever there is something wrong with the shoulder, this is transferred to the bursa. This is located between the acromion and the supraspinatus tendon and prevents the tendon from rubbing against the acromion. In osteoarthritis, it is often inflamed and also causes pain that feels like a constant burning sensation under the acromion. However, this pain is not usually felt in isolation.

Joint stiffness

Joints need to be moved. If this does not happen or happens insufficiently, for example due to osteoarthritis, the surrounding soft tissue as a whole and the joint capsule in particular may begin to shrink. The joint becomes stiff. This accelerates the progression of osteoarthritis. It is no longer possible to overcome the discomfort of starting up in the morning and the joint is barely moved throughout the day. This makes it even stiffer.

How is shoulder osteoarthritis diagnosed?

The most common complaints mentioned by a patient are pain on the one hand and limited arm function on the other. However, because many other problems show the same symptoms, it is very important to ask exactly when which symptoms exist, when and how they began and what other symptoms the patient has. It is also important to know the patient's living conditions.

The doctor will then examine you. He will try to find out where your symptoms are coming from and rule out other causes. The active and passive mobility in the joint and the function of the rotator cuff are always examined. A strength measurement is also usually included.

Further tests (for example for the biceps tendon) are carried out by the doctor as required. The questioning (anamnesis) and the examination together lead to the correct diagnosis in around 80 per cent of cases. Although the diagnosis can usually be made on the basis of the medical history and clinical examination, further examinations are required - not only to confirm the diagnosis, but also to determine the extent of the osteoarthritis and to rule out other problems. In the case of shoulder surgery, precise planning is also required, which makes further examinations necessary.

X-ray

An X-ray is quick, inexpensive and can reveal a lot about the bone, the joint and the osteoarthritis. It is therefore an almost standard part of the shoulder examination. The radiation exposure of a single X-ray is extremely low and corresponds to that of a flight to the USA.

MRI (Magnetic Resonance Imaging)

Magnetic resonance imaging is a cross-sectional imaging procedure based on the hydrogen protons in the tissue, i.e. the water content. Sectional imaging means that the part of the body to be examined is virtually divided into many millimetre-small slices. This makes it possible to see inside a solid body. Because there is little water in the bone, MRI is not very suitable for the bone. On the other hand, it is perfect for soft tissue. It can image these with great accuracy and visualise even the smallest damage. The best way to do this is to inject a little contrast agent into the shoulder joint beforehand. And the brilliant thing about it: the MRI does not require any X-rays at all. It is the most important diagnostic tool for the shoulder. In the case of osteoarthritis, for example, it shows us whether the rotator cuff is still intact or no longer intact.

Computer tomography (CT)

This also produces cross-sectional images, but on the basis of X-rays. It is indispensable when it comes to reconstructing a bone or its damage in three dimensions. This is why it is often used to plan the implantation of a prosthesis. As it is less good at imaging soft tissue than MRI, it is used less frequently in the shoulder. The radiation exposure is significantly higher than that of a simple X-ray, but is still far from being dangerous.

Ultrasound

Sonography is a technology known from bats. Using a piezo-electrode, an (ultra) sound signal is introduced into the tissue and its echo is recorded. This works excellently with soft tissue, but the sound does not pass through the bone. This is why it has its limitations in the shoulder. However, ultrasound is quick and easy to perform and is the only method that has the advantage of being able to "film" a movement in real time. This is an invaluable advantage in certain cases. In addition, the patient does not have to lie in a constricting tube, which is crucial for some patients. Ultrasound is rarely used for osteoarthritis.

Conservative treatment methods

Whenever possible, attempts are made to alleviate the symptoms without surgery (conservative treatment). This is particularly important in the early stages of osteoarthritis, when function is still well preserved but the pain is becoming noticeable.

Painkillers

Mild painkillers such as Dafalgan (paracetamol) are well tolerated and have few side effects. They are often used as the first treatment. The somewhat stronger so-called non-steroidal anti-inflammatory drugs (NSAIDs) help to alleviate inflammation, which is why they are also very popular. They also act where the pain arises and are therefore particularly suitable for use on the musculoskeletal system. Strong painkillers or opiates are only used when there is no other solution for chronic pain. They are subject to habituation (unlike the above), which means that a person tends to need more and more of them. And they are known to be addictive if taken over a long period of time. Pain ointments are rarely used on the shoulder as they can hardly penetrate the joint. The large deltoid muscle stands in their way.

Special position of cortisone

Cortisone is not actually a painkiller, but a hormone, a so-called corticosteroid. In contrast to this, the above painkillers are referred to as non-steroidal. Cortisone modulates the body's immune response and prevents inflammatory reactions. In this way it is a very potent painkiller. However, when taken as a tablet, it also has the well-known side effects such as water retention, weight gain, etc. It is often indispensable for rheumatic diseases, and the positive effect is far greater than the side effects. In osteoarthritis, it should only be used as a tablet if there is no other option and the application is short.

Cooling

Ice is an excellent painkiller, and cooling a painful joint is often the best idea. However, the ice must not be applied directly to the skin, as this can damage it. It is better to put the ice or cold pack in a plastic bag and place it in a kitchen towel. Unfortunately, the shoulder joint is surrounded by the large and powerful deltoid muscle, so the cold often cannot penetrate the joint.

Physiotherapy

Physiotherapy is one of the most important partners of shoulder specialists. It is almost always used in one form or another. In the case of osteoarthritis, it can have an analgesic, i.e. pain-relieving, effect on the one hand and keep the joint mobile on the other. It works with physical methods such as heat, cold, massage, needling or electricity and physiotherapy. Physiotherapy is essential for maintaining mobility, but also for maintaining the muscles and proprioception. The physical measures not only relieve pain, but also release muscle tension.

Infiltrations into the joint

These are another very good measure for pain relief. A mixture of cortisone and local anaesthetic is injected into the joint under X-ray or ultrasound guidance. The local anaesthetic has an immediate effect, the cortisone has a long-term effect. Because the cortisone is not taken as a tablet, which would cause it to spread throughout the body, but is only injected locally into the joint cavity, it does not have the side effects of tablets. Sometimes the patients themselves are amazed at how well such an infiltration works. An arm that has been hanging painfully from the body for weeks can suddenly be raised again - without pain! However, because every infiltration carries a (very small) risk of infection and because the cortisone can damage the intact cartilage or tendons, infiltrations are only carried out if the patient has advanced osteoarthritis or can no longer tolerate the pain.
And because the cortisone does not heal, but "only" relieves the pain, the effect is not permanent. It therefore makes sense to do physiotherapy after the infiltration so that the effect lasts longer.

Surgical treatment methods

If the above conservative treatments have been exhausted or if the restrictions are too great, then surgery must be considered.

Arthroscopy

Arthroscopy of the shoulder is a minimally invasive operation that can solve or improve many shoulder problems, but not osteoarthritis. Although there have been repeated attempts to alleviate the symptoms of osteoarthritis by cleaning and washing out a joint during arthroscopy (debridement), the successes are limited and only short-lived, meaning that the expense and risk of surgery are not worthwhile.

Joint replacement

The only good long-term solution for advanced osteoarthritis is joint replacement, i.e. a prosthesis. Prostheses have made incredible progress, especially in the shoulder. If correctly indicated and operated on, they restore mobility and relieve pain.
There are basically two types of prosthesis for the shoulder (in many different designs):

Anatomical prosthesis

This replicates the human anatomy, replacing the damaged parts of the joint but not the muscles responsible for smooth movement. It consists of a socket, which is usually made of a specially processed polyethylene and is cemented into the existing joint socket. It also includes a humeral head, usually made of cobalt chrome and titanium, which is pressed into the shaft of the humerus with its own shaft. However, this prosthesis can only function if the muscles, in particular the rotator cuff, are fully intact and functional. Unfortunately, this is rarely the case with osteoarthritis.

Inverse prosthesis

It is a masterpiece in joint care and a marvellous invention, because it does not reproduce the anatomy of the joint, but its function. And it does this by inverting the joint components. What was previously the socket is replaced by a hemisphere. This fits exactly onto its counterpart, the socket, which is implanted on the humeral head. Because this socket is deep and has a smaller diameter than the original humeral head, the system is so stable from the outset that it can partially manage without the rotator cuff - which is essential for shoulder arthrosis. Although the smaller diameter reduces mobility somewhat, it is certainly better than before the operation. And freedom from pain is guaranteed, so to speak.

These new implants are a great success story; you can use your arm again without pain after just one or two months. Because the prostheses are still being continuously adapted to the latest scientific findings, only limited information can be provided about their longevity. However, all recent studies show a longevity rate of more than 90 per cent after ten years.

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