Tendon Problems

People with diabetes are much more prone to develop problems with tendons than normal people. This is probably because the blood supply to tendons is normally pretty sparse, so very early changes in blood vessels may show up first in tendons.

Another possible explanation may be that high blood sugars appear to cause abnormal thickening of tendons. This was demonstrated in a study published in the journal, Diabetes Care.

Some common forms of tendon damage that are more common in people with diabetes and pre-diabetes are carpal tunnel syndrome, tarsal tendon syndrome (a form of carpal tunnel that strikes the feet) and frozen shoulder.

Unfortunately, very few doctors seem to be aware of this connection.
Even more unfortunately, improving blood sugars does not have an immediate effect on improving tendon problems. It may even be possible, though I have not seen this written up, that tendon problems, like other diabetic complications, may worsen at first when blood sugars are brought back to normal levels. That appears to be my own experience with these painful complications.

REFERENCES

Dr. Richard K. Bernstein's article "Some Long-Term Sequelae of Poorly Controlled Diabetes that are Frequently Undiagnosed, Misdiagnosed or Mistreated"

Carpal Tunnel May Predict Diabetes (WebMD)

Thickness of the Supraspinatus and Biceps Tendons in Diabetic Patients
Mujde Akturk, MD, Selma Karaahmetoglu, MD, Mahmut Kacar, MD and Osman Muftuoglu, MD