Rethinking My Strategies For Offloading The Achilles

An article published in Lower Extremity Review last year has caused me to reevaluate my interventions to treat pathologies of the Achilles tendon.¹ This article was authored by Groner, an excellent writer who carefully researches his work and consults with authorities in the field to validate his interpretation of published studies. Groner discusses recent research on the effects of wedging or elevation of the heel to presumably decrease load on the Achilles.

Traditionally, I have always added a ¼- to ½-inch heel lift to the inside of the shoe as a first line of treatment for Achilles tendinopathy. Not only was I trained to approach the condition this way, the intervention made sense. By plantarflexing the ankle, one could expect the length or load on the Achilles to decrease. This model would work great if the Achilles were a passive structure, which loads or offloads like a rubber band connecting two fixed objects.

The shortcoming of this theory is the fact that the Achilles is connected to the gastrocnemius and soleus muscles, which react dynamically to positioning of the leg and the foot, and are controlled by neurologic mechanisms. Changes in position of the lower extremity will cause changes in activation of the calf musculature, which can cause increased tension in the Achilles tendon. As you will see, this dynamic loading of the Achilles will far offset the minimal changes of passive offloading that occur with a simple heel lift.

In 2014, Wearing and colleagues published an eye-opening study of this concept, in which they measured Achilles tendon loads during walking barefoot in comparison to walking in a running shoe with a 10 mm heel raise or offset.² Surprisingly, the running shoe increased tensile loads on the Achilles in comparison to the barefoot condition. In a follow-up study, Wearing’s team compared walking in the same 10 mm heel offset shoe to walking in the same shoe with a 12-mm heel wedge or insert. In this study, the 12-mm heel insert reduced strain or load in the Achilles.³

How could walking in a running shoe increase loads in the Achilles in comparison to walking barefoot? Wearing’s team measured several significant gait changes (including increased step length, stance duration and peak vertical ground reaction force) that occurred while patients walked in the shoe in comparison to walking barefoot.² These gait changes, rather than the shoe itself, may have increased dynamic load in the Achilles. This increased load in the Achilles may or may not be a bad thing.

Intuitively, we want to “offload” a tendon when it is injured. However, as Groner points out in his interviews with rehabilitation experts, loading is desirable in certain phases of recovery from Achilles tendon injury. Both concentric and eccentric loading are integral parts of the Achilles rehabilitation program.^4,5 Furthermore, studies have shown that patients with Achilles tendinopathy actually have decreased activity in the triceps surae, which “under-loads” the Achilles tendon.⁶

Groner interviewed O’Neil, whose research team has measured weakness in the soleus muscle of runners with Achilles tendinopathy.⁷ O’Neil speculated that a healthy soleus provides proper loading to the Achilles, which actually protects this tendon from impact shock.¹

Other studies have shown variable effects of adding heel lifts to the shoe in an attempt to offload the Achilles. Three studies cited by Groner show that within each study group, the addition of a 10 mm heel lift could possibly increase or decrease loads in the Achilles.^8-10 Certainly, within any patient population, the response to heel lift therapy in the treatment of Achilles tendinopathy is unpredictable.

What about the effects of foot orthoses in offloading the Achilles? I am not aware of any studies that directly measured strain in the Achilles as the aforementioned studies did in focusing on heel lifts and shoes.In terms of clinical studies of the treatment of Achilles tendinopathy with foot orthoses, the results are mixed. The best study from a quality and design standpoint was by our Australian colleagues, who showed no benefit of a custom orthosis in comparison to a sham orthosis in the treatment of mid-portion Achilles tendinopathy.¹¹ All patients in this study also participated in an eccentric calf muscle exercise program, which research has proven efficacious with or without foot orthotic intervention.⁵

The bottom line for me in reviewing this research is that we still have a lot to learn about patients who suffer from Achilles tendinopathy. Some will respond well to heel lift therapy and some patients may feel the heel lift makes it worse. We need to learn more about how to identify certain subgroups of patients who will respond to heel elevation therapy. On the other hand, we know that most of these patients will respond to muscular strengthening and neuromuscular rehabilitation.^12,13 This treatment will help restore efficient loading of the Achilles, which is essential for repair and restoration of normal function.

References

1. Groner C. Achilles experts ponder effects of heel elevation. Lower Extremity Rev. April 2016. Available at https://lermagazine.com/article/achilles-experts-ponder-effects-of-heel-elevation .
2. Wearing SC, Reed L, Hooper SL, et al. Running shoes increase Achilles tendon loading in walking: an acoustic propagation study. Med Sci Sports Exerc. 2014;46(8):1604-1609.
3. Wulf M, Wearing SC, Hooper SL, et al. The effect of an in-shoe orthotic heel lift on loading of the Achilles tendon during shod walking. J Orthop Sports Phys Ther. 2016;46(2):79-86.
4. Horstmann T, Jud HM, Fröhlich V, Mündermann A, Grau S. Whole-body vibration versus eccentric training or a wait-and-see approach
for chronic Achilles tendinopathy: a randomized clinical trial. J Orthop Sports Phys Ther. 2013;43(11):794-803.
5. Jonsson P, Alfredson H, Sunding K, et al. New regimen for eccentric calf-muscle training in patients with chronic insertional Achilles tendinopathy: results of a pilot study. Br J Sports Med. 2008;42(9):746-749.
6. Azevedo LB, Lambert MI, Vaughan CL, O’Connor CM, Schwellnus MP. Biomechanical variables associated with Achilles tendinopathy in runners. Br J Sports Med. 2009;43(4):288-292.
7. O’Neill S, Watson P, Barry S. Plantarflexor muscle power deficits in runners with Achilles tendinopathy. Br J Sports Med. 2014;48(Suppl 2):A49.
8. Reinschmidt C, Nigg BM. Influence of heel height on ankle joint moments in running. Med Sci Sports Exerc. 1995;27(3):410-416.
9. Dixon SJ, Kerwin DD. Variations in Achilles tendon loading with heel lift intervention in heel-toe runners. J Appl Biomech. 2002;18(4):321-331.
10. Low D, Dixon S. The effect of a heel insert intervention on Achilles tendon loading during running in soccer. Sport Exerc Med. 2015;1(6):167-173.
11. Munteanu SE, Scott LA, Bonanno DR, et al. Effectiveness of customised foot orthoses for Achilles tendinopathy: a randomized controlled trial. Br J Sports Med. 2015;49(15):989-994.
12. Jonsson P, Alfredson H, Sunding K, et al. New regimen for eccentric calf-muscle training in patients with chronic insertional Achilles tendinopathy: results of a pilot study. Br J Sports Med. 2008;42(9):746-749.
13. Chang Y-J, Kulig K. The neuromechanical adaptations to Achilles tendinosis. J Physiol. 2015;593(15):3373-3387.