What Is the Cause of Shoulder Pain?

Most of the time, pain in the shoulder comes from overuse. If you look at the picture of the shoulder with the deltoid (that’s the big muscle that covers your whole shoulder joint) removed, you will see that your arm bone, your humerus sits underneath the top of your shoulder blade and that the muscles that move the shoulder all start out attached to the shoulder blade and have to travel under that bony bridge to move your humerus (your arm bone).
If your shoulders slump forward, or if the bridge is crooked, these muscle tendons will be squeezed between the humerus and your shoulder blade every time you move your shoulder. The tendon at the very top of the humerus is the supraspinatus tendon and is the one most likely to be damaged. When you raise your arms, the squeezing gets worse. This will eventually wear out the tendons and cause a great deal of pain. The muscles that get squeezed are called the rotator cuff, because they help your shoulder rotate and keep it in its socket. The wearing out of the rotator cuff tendons is called rotator cuff syndrome.
Ligaments and tendons are made up of collagen, the same substance that holds up your skin, and, just as your skin loses its tone as you get older, so do your ligaments and tendons. Because of this, as you get older, the ligaments and tendons that surround your shoulder joint get looser and weaker. This means the head of your humerus will move too much inside the shoulder joint and wear out the cartilage which lines the joint. In order to try and stabilize your shoulder, the bones around the joints will start to grow. This thinning of the cartilage and the growth of the surrounding bone is called osteoarthritis. It can also be a source of pain. Another joint in your shoulder area that can develop arthritis is the joint between the acromion and your clavicle called the acromioclavicular joint. Pain due to loose ligaments or tendons or arthritis only comes when you move the ligaments or tendons or the joints.
Nerve damage can also cause shoulder pain. The nerves in the neck can send pain messages to the shoulder. Sometimes the nerves that supply the skin of the shoulder can be injured through a sudden jolt, or through a whiplash injury to the neck. The nerves that supply the skin of your shoulder have to cross the fascia, the fibrous sheath covering the muscles at the base of the neck through tiny holes. Whiplash, or a sudden pull on the arm stretches the fascia and distorts these holes, which become slits. These slits squeeze the nerves and cause them to swell. Once swollen, the nerves are trapped in these holes and cannot slim down, as they keep re-injuring themselves on the walls of these holes, and every time they injure themselves, they swell even more. As long as they remain swollen, these nerves will send pain messages to the brain. This pain can spread down the arm, first to the elbow then to the hand, and can last for many years. Nerve pain can be severe and happen at any time, even when you are not moving at all. If you press lightly on an area with nerve pain, the pain gets worse.

What Are the Treatments for Shoulder Pain?

Prolotherapy, a series of injections of growth promoting substances has been shown to be effective in stimulating the growth and repair of ligaments and tendons. Injections to the shoulder ligament and tendon insertions strengthen and thicken them. These stronger ligaments and tendons will help restore the strength of your shoulder and help correct the cause of shoulder pain. Prolotherapy has been shown to reduce the overgrowth of bone which occurs in osteoarthritis of the fingers and of the knee. It probably does so because it stabilizes the joints by strengthening the ligaments that surround them. This reduces the wear and tear on the joints which is the main reason bones around the joints proliferate. If this occurs in your shoulder it may help prevent the onset of osteoarthritis of your shoulder joint.
If you have tried other treatments and still experience pain, you may want to try prolotherapy. There is a good chance that prolotherapy can bring you relief from your shoulder pain. There have unfortunately not been any “gold standard” studies done to prove the value of prolotherapy in rotator cuff problems. This is why Dr. Bertrand has carried out and published such a “gold standard” study, funded by work safe BC and approved by the UBC ethics committee. It shows that those who got prolotherapy, together with physiotherapy, got twice as much long-term pain relief as those who were only treated with physiotherapy.

Treatment of shoulder pain with perineural injection therapy (nerve blocks ) is very effective in providing relief, and allowing you to start moving your shoulder again. It is particularly effective for those who suffer from “frozen shoulder”, or shoulder pain associated with neck pain. It is likely to help, if your pain is coming from the nerves that supply the skin of your shoulder. Nerve pain can be severe even when you are resting and can be made worse by pressing lightly on the affected areas. Often, people have pain in their neck, back or chest as well as shoulder pain, because the nerves that supply the skin of the shoulder come from the neck and also supply the back and the chest. In both these cases, the pain, and difficulty moving the area is due to inflammation of the nerves which supply the area, and perineural injection therapy relieves this inflammation. It consists in bathing the nerves which supply the skin and the shoulder joint, with a dextrose or mannitol solution, which is injected with a tiny needle just under the skin. Dextrose and mannitol are derived from sugar, and sugar blocks the receptor on the skin nerves which causes these nerves swell and is associated with pain and inflammation. When that receptor is blocked, the swelling and inflammation associated with these nerves disappears. When the nerves regain their normal function, there is no more pain and the shoulder itself also regains normal function. Because this treatment is very safe, it is worth trying at least once, particularly if your pain has not been helped by other treatments.
Acetaminophen, Tylenol, which has a mild anti-inflammatory effect, and anti-inflammatory medications such as aspirin, ibuprofen, Advil, Motrin have, until now, been the mainstay of treatment to relieve shoulder pain. They all relieve the symptoms that occur with overstretched and worn ligaments and tendons. They work by relieving inflammation which is a cause of pain. Unfortunately, inflammation is the mechanism the body uses to repair itself, and using these medications interferes with the process which would help regrow the affected ligaments and tendons. Nonsteroidal anti-inflammatory references

People who have suffered from intractable shoulder pain are often given cortisone shots. These, being even more powerful anti-inflammatory substances, unfortunately also interfere with healing of the shoulder and can at times cause rupture of shoulder tendons. Steroid References

Physiotherapy helps shoulder pain by improving your posture so that your rotator cuff muscles don’t get squeezed as much between your humerus and your acromion, and strengthening the muscles which stabilize your shoulder. Unfortunately, it is impossible to strengthen ligaments and tendons with exercise. Since your muscles are pulling on these weakened ligaments and tendons, your symptoms are likely to recur.

Surgery may be needed in refractory cases, particularly if one of the shoulder tendons has been completely ruptured, or if the acromion is crooked. More and more, orthopedic surgeons are performing keyhole surgery to help repair these structures. In Canada, the wait to see a shoulder specialist can be more than one year. In all countries, surgery can be very costly.

Narcotics can be used to deaden the pain and do not interfere with inflammation, but they can be addictive and should be used very sparingly.

How Effective are These Treatments?

Statistics show that 54% of those who have a rotator cuff problem will still be in pain and have limited use of their shoulder after three years. Over 75% will be better with prolotherapy or perineural injection therapy.

References on the shoulder

Lewis JS Rotator cuff tendinopathy / subacromial impingement syndrome: Is it time for a new method of assessment? Br J Sports Med Oct 2008 Shows how long the disability from rotator cuff injuries and tears will last, mostly because people don’t understand the underlying pathology
Rathbun JB, Macnab I: The microvascular pattern of the rotator cuff. J Bone Joint Surg Br 1970;52:540-553. Shows how poor the circulation is to the supraspinatus tendon

Google: American Academy of orthopedic surgeons: Rotator Cuff Tears: Frequently Asked Questions A good overview of how effective the currently available treatments are, and what are their possible risks and side effects

J.Carpenter, S.Thomopoulos, C.Flanagan, C.DeBano, L.Soslowsky Rotator cuff defect healing: A biomechanical and histologic analysis in an animal model Journal of Shoulder and Elbow Surgery, Volume 7, Issue 6, Pages 599-605 Shows that left on their own tendons healed very poorly

Prolotherapy References

Bertrand H, Reeves KD, Bennett CJ, Bicknell S, Cheng A-L, Dextrose Prolotherapy versus Control Injections in Painful Rotator Cuff Tendinopathy. Arch Phys Med Rehabil 2016;97: 17-25, doi: 10.1016/j.apmr.2015.08.412.)