Diabetes is known to affect the shoulder in several ways. Frozen shoulder seems to be the commonest - with up to 20% of diabetic patients developing it at some time or other.

Calcium spots in the tendons and muscle around the shoulder are also seen more commonly in diabetic patients - this probably relates to the fact that high blood sugars can impair blood flow through small vessels. Tendons are particularly vulnerable to this and respond by depositing calcium. These calcium deposits can sometimes be painless but often cause severe discomfort or limited movement. They usually show up on x-rays.

Slow healing and impaired nerve function are also common in diabetic patients and contribute to the fact that the pain takes longer to settle than it does in other, non diabetic, patients.

Diabetic patients are much more likely to have problems with their shoulders than others. Insulin dependant diabetics are particularly at risk - with some studies showing that they are six times more likely to have these problems than the rest of the population.

I don't know why these problems arise but it seems to relate in part to how well each individual controls their blood sugar levels.

Textbooks tell you that all shoulder complaints are more common in diabetes but in my experience frozen shoulder is the most troublesome and most frequent. Diabetics not only get frozen shoulder more often than others but it lasts longer and is more painful for them when they do.

Some experts think that shoulder problems in diabetics are so common that they should be regarded as a complication of diabetes and not a coincidental event.

There has been a lot of research recently but it is still rather unclear why diabetic patients get such problems with their shoulders. It seems to relate to the effect that diabetes and a high blood sugar has on the collagen containing cells in the body. Collagen is a protein that is involved in making ligaments, tendons and - of course - joint capsules.