Plantar fasciitis is one of the most common injuries and the leading cause of heel pain for runners. It has been estimated that plantar fasciitis affects roughly 10% of runners every year.
Many runners will be able to overcome this painful condition, often using self treatment strategies such as stretching their calves, strengthening their foot intrinsic muscles, rolling their plantar fascia with a golf ball or lacrosse ball, or even wearing a night splint. Some runners, unfortunately, won’t recover with these interventions. They may have even changed shoes, tried different orthotics, and received treatment directed at their plantar fascia from multiple healthcare providers, yet remain symptomatic.
True plantar fasciitis is due to irritation of the plantar fascia where it attaches to the heel bone. While this is the most common reason for heel pain that gets diagnosed as plantar fasciitis, several other conditions can cause similar symptoms. One of these is aggravation of the nerves of the inner foot and ankle. Nerve irritation needs to be treated much differently than true plantar fasciitis, making it very important to differentiate the cause.
True Plantar Fasciitis Vs. Neurogenic Plantar Fasciitis
At first glance, true plantar fasciitis (due to irritation of the plantar fascia attachment) may be hard to distinguish from what can be called ‘neurogenic’ plantar fasciitis (due to irritation of the posterior tibial and plantar nerves). Both conditions cause pain on the arch side of the heel that is aggravated with weight bearing activities such as standing, walking, and running. Due to busy schedules and insurance constraints, many healthcare professionals are being forced to spend less time with patients. They may not have the time to accurately discern between true and neurogenic plantar fasciitis, and patients are simply diagnosed with the broad label of plantar fasciitis. While these diagnoses are best confirmed by medical professionals, knowing what to look for and how to manage neurogenic plantar fasciitis will help you become your own biggest advocate in the treatment of your heel pain.
The posterior tibial and plantar nerves are part of the sciatic tract, which runs from the spine to the tips of the toes. Therefore, anything that tensions the sciatic nerve will also affect the posterior tibial and plantar nerves. The sciatic nerve is tensioned by the same movements that stretch the hamstrings, especially when combined with movements that stretch the calf muscles. The posterior tibial and plantar nerves are further tensioned by rotating the heel so the bottom points outward and by lifting the toes.
How to Test
There are several clues that could help you determine if nerve irritation is contributing to your heel pain.
- Heel pain that is produced or increased when stretching your hamstrings, especially when you add pointing your toes back toward you and turning your heel outward to the stretch.
- Heel pain that is produced or increased when stretching your calves on a step or curb with your knee straight.
- Heel pain that is produced or increased just prior to heel strike during running, when the hip is flexed and the knee is straight.
Basically, you likely have posterior tibial or plantar nerve involvement if symptoms similar to plantar fasciitis are produced or increased when the sciatic tract is tensioned.
Several other signs and symptoms may help rule in nerve involvement, including:
- Pain that is described as a burning type sensation.
- Pins and needles, in addition to pain.
- Tenderness along the nerve as it courses behind the inside ankle bone and into the bottom of the foot.
- A positive Tinel’s test. This is where symptoms are reproduced by tapping on the affected nerve just behind the inside ankle bone.
- Swelling of the inner heel.
Similar to other tissues in the body, in order to remain healthy, nerves must be able to move freely relative to their surrounding tissues. If these adjacent tissues become dysfunctional, it may lead to increased compression or impaired mobility of the nerve, resulting in adverse neural tension. The posterior tibial nerve is most susceptible in the tarsal tunnel, just behind the inside ankle bone. The medial and lateral plantar nerves are most susceptible as they course under the muscle that forms the back of the arch.
How To Treat
Neurodynamic exercises known as sliders are a great way to promote healthy movement of the nervous system relative to their surrounding tissues. These don’t cause excess tension in the involved nerves, and (in healthy individuals) should be painless. They can be a great way to potentially prevent entrapment of the posterior tibial and plantar nerves and therefore symptoms of neurogenic plantar fasciitis.
The following exercises provide a couple of great slider options. Each exercise has two parts.
1) Standing Slider
The first exercise is performed standing. Place your heel on a knee high bench or step, and keep this knee straight throughout the exercise. First, tilt your head backward while simultaneously pointing your foot and toes toward you. This moves the involved nerves toward the toes. Next, move your head toward your chest while simultaneously pointing your elevated foot and toes away from you. This moves the involved nerves toward the knee. This makes one rep.
2) Back Slider
For the second slider exercise, begin by laying on your back. While keeping your knee straight, raise your leg to the point where you feel hamstring tension. Use your hands to maintain this angle of your thigh throughout the exercise. Then, first bend your knee to 90 degrees and point your foot and toes toward you. This moves the involved nerves toward the toes. Next, extend your knee and point your foot and toes away from you. This moves the involved nerves toward the knee. This is one rep.
Perform these movements back and forth slowly as one continuous fluid motion. You can do up to 10 repetitions of a slider exercise at a time. The goal is to move the nerves back and forth relative to potential sites of irritation in the foot and ankle that can lead to neurogenic plantar fasciitis. Nerves that move well are less susceptible to sustaining entrapment injuries.
A leg swing is another exercise for the sciatic tract that has a neurodynamic effect and helps promote healthy nerve movement. Swing your leg forward and back while keeping your knee straight and your foot at a 90 degree angle to your lower leg. Start out with slow, small swings and progress to swinging as high as you comfortably can. Stop if you provoke heel symptoms with this exercise, as it creates more tension on the sciatic tract than the previously mentioned sliders. When performed pain free, leg swings can help promote resiliency and mobility of the nervous system.
If you suffer from symptoms resembling plantar fasciitis and continue to have pain despite treatment, especially if you have any of the signs and symptoms mentioned above, you should seek out care from a sports medicine professional knowledgeable in the diagnosis and treatment of neurodynamic problems. Because of their ability to mimic true plantar fasciitis, the posterior tibial and plantar nerves should absolutely be assessed in all patients with heel pain.
About the Author
Jordan Duncan is a sports and rehabilitation chiropractor practicing in the Seattle area. In addition to treating runners, he has completed several marathons and numerous shorter distance races. Learn more about him at silverdalesportandspine.com.