A Closer Look At Stretching For Equinus In Patients With Diabetes

Reading an article’s title without taking a deeper dive is a tenuous exercise at best. A perfect example of this is a new article in Clinical Biomechanics titled, “Calf muscle stretching is ineffective in increasing ankle range of motion or reducing plantar pressures in people with diabetes and ankle equinus: A randomised controlled trial” by Searle and colleagues.1 With my interest in equinus, this article certainly peaked my attention.

Over the past few years, Searle and colleagues have produced significant research on equinus in patients with diabetes.2,3 In a meta-analysis, they examined the association between equinus and plantar pressures in patients with diabetes.2 Three studies met the inclusion criteria for the meta-analysis and the authors found that “equinus has a significant, but small, effect on increased plantar pressures.”2 The study authors concluded:

“Limited ankle joint dorsiflexion may be an important factor in elevating plantar pressures, independent of neuropathy. Limited ankle dorsiflexion and increased plantar pressures were found in all the studies where the sample population had a history of neuropathic foot ulceration. In contrast, the same association was not found in those studies where the population had neuropathy and no history of foot ulcer. Routine screening for limited ankle dorsiflexion range of motion in the diabetic population would allow for early provision of conservative treatment options to reduce plantar pressures and lessen ulcer risk.”2

In the follow-up article, Searle and coworkers studied the prevalence of equinus using a validated method and then determined the association between peak plantar pressures and equinus.3 They defined equinus as less than or equal to five degrees of ankle joint dorsiflexion with the knee extended. Of the 136 patients with diabetes included in the study, 66.9 percent met the criteria for equinus. Barefoot, in-shoe forefoot pressure time integrals and in-shoe forefoot alternate pressure time integrals demonstrated a statistically significant association with equinus.3 Men, those with diabetic neuropathy and those with higher glycated hemoglobin (HbA1C) levels were more likely to have equinus.

Higher HbA1C levels linked to higher rates of equinus makes sense in the patient group with diabetes. These patients have the anatomical, functional and evolutionary factors associated with the development of equinus, but they also have a metabolic component to their equinus as well.4-7 Searle and colleagues concluded:

“Community dwelling adults with diabetes have a high rate of ankle equinus, which is associated with increased forefoot pressure time integrals and a twofold increased risk of high in-shoe peak pressures. Clinical assessment of an ankle equinus may be a useful screening tool to identify adults at increased risk of diabetic foot complications.”3

In the most recent study by Searle and coworkers, the researchers used validated non-weightbearing and weightbearing measurement methods to diagnose equinus in 68 patients with diabetes.1 Researchers subsequently compared a control group to a treatment group that performed manual stretching for two minutes per day, five days a week over eight-week period for a total of 80 minutes of therapy. At the completion of the study, the authors noted no significant difference between the stretching group and control group for ankle range of motion or plantar pressures.

Some misleading information have been surfacing regarding the results of this study, basically saying stretching is ineffective in patients with diabetes. That is simply not true. What this study shows is two minutes of stretching per day for five days a week over an eight-week period is not effective. The Radford and colleagues study referenced in the article as the basis for therapy does not actually make any recommendations on the amount of time required to stretch.8 This systematic review examined three treatment groups who stretched less than 15 minutes, 15 to 30 minutes and greater than 30 minutes. The review authors did not evaluate a two-minute stretching program. Radford and team concluded: “Calf muscle stretching provides a small and statistically significant increase in ankle dorsiflexion. However, it is unclear whether the change is clinically important.”8

It is important to avoid conflating these results. Research on the use of gastroc-soleus complex lengthening to alleviate diabetic forefoot pressure ulcerations is robust. Why would surgical lengthening work while conservative lengthening does not? In regard to the critical concepts on stretching in the patient with diabetes (a functional and metabolic deformity), the patient must stretch long enough each day for an adequate duration and once the equinus has resolved, one must utilize maintenance therapy to preserve the correction.

I use a one hour per day stretching regime over a 12-week therapeutic period to help treat equinus. Once there is full correction of the deformity (greater than five degrees ankle dorsiflexion with the foot fully supinated and the knee extended), then one transitions the patient to maintenance therapy of stretching one hour per day three nights per week. Anecdotally, by using this approach for numerous patients (including those with diabetes), I have found in my experience that you can correct the deleterious effects of equinus conservatively.

Dr. DeHeer is the Residency Director of the St. Vincent Hospital Podiatry Program in Indianapolis. He is a Fellow of the American College of Foot and Ankle Surgeons, a Fellow of the American Society of Podiatric Surgeons, a Fellow of the American College of Foot and Ankle Pediatrics, a Fellow of the Royal College of Physicians and Surgeons of Glasgow, and a Diplomate of the American Board of Podiatric Surgery. Dr. DeHeer discloses that he is the inventor of The Equinus Brace® and an owner of IQ Medical.

References

1. Searle A, Spink MJ, Oldmeadow C, Chiu S, Chuter VH. "Calf muscle stretching is ineffective in increasing ankle range of motion or reducing plantar pressures in people with diabetes and ankle equinus: A randomised controlled trial." Clin Biomech. 2019;69:52-57.
2. Searle A, Spink MJ, Ho A, Chuter VH. Association between ankle equinus and plantar pressures in people with diabetes. A systematic review and meta-analysis. Clin Biomech.  3017;43:8-14.
3. Searle A, Spink MJ, Chuter VH. Prevalence of ankle equinus and correlation with foot plantar pressures in people with diabetes. Clin Biomech. 2018;60:39-44.
4. Amis J. The gastrocnemius: a new paradigm for the human foot and ankle. Foot Ankle Clin. 2014;19(4):637-647.
5. Amis J. The split second effect: the mechanism of how equinus can damage the human foot and ankle. Front Surg. 2016;3:38.
6. Somai P, Vogelgesang S. Limited joint mobility in diabetes mellitus: The clinical implications. J Musculoskelet Med. 2011;28(4):118.
7. Grant WP, Sullivan R, Sonenshine DE, et al. Electron microscopic investigation of the effects of diabetes mellitus on the Achilles tendon. J Foot Ankle Surg. 1997;36(4): 272-278.
8. Radford JA, Burns J, Buchbinder R, Landorf KB, Cook C. Does stretching increase ankle dorsiflexion range of motion? A systematic review. Br J Sports Med. 2006;40(10):870-875.