Plantar Fasciitis or Flexor Digitorum Brevis Myositis

As common as plantar fasciitis is, there's a lack of evidence regarding the true pathophysiologic process causing plantar fasciitis and plantar heel pain in general. This may partially explain the high variability and outcomes with current treatment of recalcitrant plantar fasciitis. Although Lemont reported myxoid degeneration of plantar fascia with histologic analysis of patients with fasciitis, muscle biopsy results were not reported. So far it appears we have not focused on the muscular component that may be present with plantar heel pain in general and in patients we diagnose with plantar fasciitis in particular.

In this article we performed a retrospective analysis of biopsy results from five patients with the diagnosis of recalcitrant plantar fasciitis to determine whether this diagnosis was correct or whether other component pathologies contribute to the chronicity of symptoms or to the failure of treatment.

Three of the five pathology reports included specific mention of inflammation, degeneration and atrophy of the intrinsic musculature consistent with myositis. Two of these showed lymphocytic infiltration in the muscle consistent with inflammation, with no signs of inflammation in the fascia. One showed inflammation of the fascia without signs of inflammation of the muscle.

This small study introduces the idea that intrinsic myositis may contribute to, or be responsible for some cases of plantar heel pain and plantar fasciitis. This may be important in changing the way we deal with plantar heel pain in the future.