Diabetes Patients May Be At Increased Risk of Tendinopathy
For patients living with type 2 diabetes, regular exercise is a key to keeping blood sugar levels normal.1 However, musculoskeletal complications oftentimes sabotage a healthy exercise regimen. About 50% of patients with diabetes have to stop exercising because of musculoskeletal pain, and tendinopathy is typically the delineating factor.2
Now a new study has found that people with diabetes are at far higher risk of developing tendinopathy compared with people without diabetes.3 Duration of disease and thicker tendons appear to be associated with tendinopathy in diabetes.
These associations may help clinicians better understand tendinopathy as a whole, as well as why it happens and how it can be avoided.
Diabetes and Tendinopathy
A team of Australian researchers conducted a meta-analysis, searching for studies that included at least one tendon-related and one diabetes-related variables, and excluding any studies that did not use a control group.3 After sorting through over a 1,000 papers, they focused their review to 31 studies.
The researchers found that people with diabetes were more than 3 times at risk of developing tendinopathy compared to controls (Odds Radio: 3.67), regardless if the tendinopathy was diagnosed by imaging or clinical criteria. In addition, diabetes was more prevalent in people with tendinopathy than in those without tendinopathy (OR 1.30).
In 6 studies, patients with diabetes and co-occurring tendinopathy had a longer duration of diabetes compared to patients with diabetes but no tendinopathy (Medium duration, 5.26 years). Whether this suggests long-term diabetics are at higher risk for tendinopathy is a supposition, though.
Tendinopathy: A Developing Etiology
The results point to an interesting association between diabetes and tendinopathy. However, the etiology of tendinopathy is a developing topic. According to Jamie E. Gaida, PhD, an associate professor at the University of Canberra, how tendinopathy biologically occurs could require a multi-faceted answer.
Elevated blood glucose levels, increased cholesterol, adiposity, statin use—all of these are confounders to a direct causal link between tendinopathy and diabetes.4-6 “Each of these factors has been shown to predispose to tendinopathy, so it is reasonable to consider that they may all contribute to the increased rates seen in people with diabetes,” Dr. Gaida told Practical Pain Management.
This “net effect” could be the explanation as to why people with diabetes seem to commonly experience a decreased tolerance to mechanical loading, or overload syndrome. “In my mind, the key to understanding this area is to appreciate that metabolic factors can reduce the capacity of the tendon to tolerate load,” which could lead to a failing of the tendons’ innate healing response, he said.
Interestingly, people diagnosed with diabetes seemed to have thicker tendons compared to controls. However, there were also statistically significant differences between the diagnosis subgroups (diagnosed via imaging versus clinical criteria; P<0.001), which may have indicated that the effect variated in different tendons.
This increased tendon thickness is a “central finding in people with tendinopathy,” Dr. Gaida said. The prevailing idea is that the increased cross-sectional area distributes the mechanical force over a larger amount of tissue, thus reducing the load.7
“An analogy is that if you are towing a car and notice the rope is starting to fray and become damaged, the first thing you do is get a bigger rope. The tendon is doing the same thing,” Dr. Gaida said.
However with diabetics, the initial insult is a metabolic one, not mechanical, so the implicating factors could be a number of things, like collagen cross-linking in the tendon or the increased cytokine levels common to diabetes. Oxidative stress on the tendon cells could also be a factor.8
“I have to wonder if this is correlated to microangiopathy experienced in diabetic patients,” Joseph J. Ruane, DO, a medical director at the McConnell Spine, Sport, and Joint Center in Columbus, Ohio, told Practical Pain Management. The tendons can become poorly vascularized, compromising the blood supply and resulting in an abnormal physiologic response of thickening and tendinopathy.
Indeed, impaired microvascular function is commonly found in obese patients, Dr. Gaida noted, the explanation being that additive or individual effects of hypertension, insulin resistance, and dyslipidaemia contribute to a reduced function of small blood vessels. “We keenly await studies in this area to clarify the effect of each of the proposed factors and how they interact.”
Tendinopathy in the Clinical Setting
“People with diabetes should absolutely be physically active, as it is one of the most effective management strategies for diabetes,” said Dr. Ruane. However, the manner in which a patient engages in physical activity is critical.
Not overloading the tendons with an unbalanced exercise regimen is important. Patients should ease into the intensity of their workouts and focus on keeping to achievable goals. Tendons respond better to consistent activity, not bouts of intensity followed by sedentary periods, Dr. Gaida said.
According to Dr. Ruane, if a patient is experiencing tendon pain, he or she should be evaluated and treated early, especially if the tendon pain lasts for more than 6 weeks. “I used to think this was overkill and poor use of medical resources. However, treatment of tendinitis is much, much easier than treatment of tendinopathy—and much cheaper, too.”
The key is to address the issue while the tendon is still just painful, not pathologic. “The diagnosis is easy, the real question is why are they getting tendon dysfunction in the first place?” Improper training could be an explanation; there also could be anatomic issues requiring orthotics," he noted.
“Managed correctly, many tendon symptoms can either become quiescent, or at least reduced to the point where they do not impair daily function and exercise,” said Dr. Ruane. Patients are on the right track if the tendon pain subsides. “That does not mean the tendon returns to normal, it just stops hurting. That can take up to 18 months, however.”
Current nonsurgical tendinopathy treatments are based around rehabilitation and deep tissue techniques. “It has been shown that eccentric exercise training, as well as deep friction massage (which includes all similar techniques such as Graston, ART [Active Release Techniques], Rolfing, etc.) can stimulate biologic mechanisms of repair.
“Pharmacologic therapy does not do much, and continued use of anti-inflammatory drugs can even be counterproductive. In tendinopathy, ‘inflammation’ is not the pain generator, and the NSAIDs don't do much more than Tylenol would, and of course there is the kidney and gastrointestinal risk. I will stop short of interventions such as platelet rich plasma and ultrasound guided percutaneous tenotomy, which are considered if the aforementioned fail,” Dr. Ruane said.