Foot drop is the common term to describe the difficulty a patient may experience in lifting and bringing the hind foot forward during the toe-off phase of gait. As a result, the distal phalanges end up dragging or scraping the ground as the motion occurs. This has been linked with muscle weakness in ankle dorsiflexors and other contributing muscles: tibialis anterior, fibularis tertius, extensor digitorum longus and extensor hallucis longus. Patients experiencing this drag usually develop a habit of lifting their thigh into a more flexed position than normal to compensate.

Causes of foot drop

Importantly, foot drop may also be a sign of a more urgent neurological, muscular or anatomical injury or disorder. The most common cause of these is the compression of the peroneal nerve that runs along the anterior and lateral portions of the fibula and tibia respectively. This compression essentially affects the muscles of the lower leg and may be a cause of hip or knee replacement surgery.

Less commonly, foot drop may also be a result of a “pinched nerve” in the spine, muscular dystrophy, polio, Charcot-Marie-Tooth disease, ALS, MS, stroke (Mayo Clinic 2017), tumors or cysts that apply pressure to the region (Berkit et al. 2018) or even significant weight loss (Evans et al. 2013). Some researchers have discovered more less common causes to foot drop, i.e. gunshot wounds (Nath et al. 2017).

How many cases of foot drop occur per year?

Because foot drop is a symptom of so many disorders, tracking the number of cases is difficult using the World Health Organization’s ICD coding M21.37 (ICD-10), but currently in progress at the time of this article’s publication. According to a 20 year study of MS in the UK, there has been a 2.4% increase per year (MacKenzie et al. 2014) and approximately 31% of MS cases possess a difficulty with walking, with some causation linked to foot drop (Taylor et al. 2016). The Gale Encyclopedia of Neurological Disorders states that foot drop is more common in males (approx. ratio m:f; 2.8:1), mid-aged athletes and those with surgical nerve damage (3-13%). I myself have treated 15 patients who experienced varied degrees of foot drop in 2018. However as of 2004, no clinical trials of foot drop were produced, though the National Institute of Neurological Disorders and Stroke has shown support into the subject (Gale Group 2004).

Treatment for foot drop

This ailment may be a temporary result from prolonged kneeling or leg crossing, but can also be permanent. Common diagnosis tests include visual observation of the altered behavior of the thigh and foot during phases of gait and analyses of blood for diabetes, alcoholism, toxin, fasting blood sugar, hemoglobin determination and quantities of nitrogen and creatinine. Along with physical therapists, a special AFO brace is the best solution to provide normal range of motion. Surgery, by relieving pressure, repairing a muscle or lengthening/replacing the achilles tendon, can only benefit a patient if drop foot has been diagnosed correctly as a muscular or nerve difficulty.

ICD diagnosis codes for foot drop

ICD-10:

M21.371 – foot drop, right foot

M21.372 – foot drop, left foot

ICD-9:

736.79 – foot drop

References & Literature Cited

Berkit, I. K., Turan, Y., Bayraktar, K. 2018. “Peroneal Nerve Palsy due to Synovial Cyst of Proximal Tibiofibular Joint,” Meandros Medical and Dental Journal 19: 254-258. https://www.semanticscholar.org/paper/Peroneal-Nerve-Palsy-due-to-Synovial-Cyst-of-Joint-Berkit-Turan/80db04f19ca0eefe56de7415fa8ae303f1a4c6b2.

Evans, J. W., Sell, E., Lewis, E. C. 2013. “Case 1: Foot drop and numbness in a 16-year-old girl,” Paediatrics & Child Health Vol. 18, 10: 515-516. https://academic.oup.com/pch/article/18/10/515/2682983.

Mackenzie, I. S., Morant, S. V., Bloomfield, G. A., MacDonald, T. M., O’Riordan, J. 2014. “Incidence and prevalence of multiple sclerosis in the UK 1990-2010: a descriptive study in the General Practice Research Database,” Journal of Neurology, Neurosurgery & Psychiatry 85: 76-84. https://jnnp.bmj.com/content/85/1/76.

Martin, E., McFerran, T. 2008. “Foot Drop,” A Dictionary of Nursing, Gale Encyclopedia of Disorders. Accessed 12 Feb. 2019. https://www.encyclopedia.com/medicine/diseases-and-conditions/pathology/foot-drop.

“ICD-10 Diagnosis Code M21.37,” ICD List. Accessed 9 Feb. 2019. https://icdlist.com/icd-10/M21.37.

Mayo Clinic. 2017. “Foot Drop,” Mayo Clinic. Accessed 9 Feb. 2019. https://www.mayoclinic.org/diseases-conditions/foot-drop/symptoms-causes/syc-20372628.

Nath, R. K., Somasundaram, C. 2017. “Gait Improvements After Peroneal or Tibial Nerve Transfer in Patients with Foot Drop: A Retrospective Study,” Eplasty. https://www.researchgate.net/publication/320188252_Gait_Improvements_After_Peroneal_or_Tibial_Nerve_Transfer_in_Patients_with_Foot_Drop_A_Retrospective_Study.

Taylor, P. N., Wilkinson Hart, I. A., Khan, M. S., Slade-Sharman, D. E. M. 2016.  “Correction of Footdrop Due to Multiple Sclerosis Using the STIMuSTEP Implanted Dropped Foot Stimulator,” International Journal of MS Care Vol 18, No. 5: 239-247. https://ijmsc.org/doi/10.7224/1537-2073.2015-038.

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Kevin B. Rosenbloom, C.Ped, Sports Biomechanist

Kevin B. Rosenbloom, founder, and president of KevinRoot Medical, is a renowned certified pedorthist and sports biomechanist practicing in Santa Monica, CA. With his continuing research on the historical development of foot and ankle pathologies, comparative evolution of lower extremities and the modern environmental impacts on ambulation, he provides advanced biomechanical solutions for his patients and clients.