Plantar fasciitis is most common between the ages of 40-60 with around 3 million cases a year. It is especially common in the running community with up to 10% of runners affected by it. The plantar fascia works with the Achilles tendon to store and release energy, as well as helps stabilize the foot during the push-off phase of walking/running. This is important to understand because during the push-off phase of running the plantar fascia is exposed up to 7 times your bodyweight. That is a lot of stress for one tissue to be repetitively exposed to.
Thankfully our bodies are smart and have built in safety mechanisms to help absorb and distribute loads. In the case of the plantar fascia its back up is a little muscle in the foot called the flexor digitorum brevis (FDB). The plantar fascia passively stores and returns energy, while the FDB plays a dynamic role in variable load sharing. In simple terms the FDB works to share the load with the plantar fascia to reduce amount of stress placed on it.
One of the problems with many individuals with plantar fasciitis is they have weak FDB. Meaning they are unable to help reduce the amount of forces placed on the plantar fascia during the push-off phase. For many years it has been hypothesized this increased stress placed on the plantar fascia is what caused heel spurs. However, in a study of individuals with heel spurs they found the heel spurs were really coming from the origin of the FDB muscle. While additional research has found that a better predictor for plantar fasciitis is not flattened arches, but rather strength of FDB. These studies show the strong relationship between the plantar fascia and FDB muscle.
One way to see if you need to strengthen your FDB is look at your running shoes, runners who tend to have strong FDB have clear indents beneath their little toes on their insoles. An alternative method to test FDB strength is the paper grip test. Sit down with the hips, knees, and ankle flexed at 90 degrees. Place paper/card underneath the 2nd to 5th little toes and try to not let the card be pulled out from under your toes. Individuals with a weak FDB will struggle to prevent the card from being pulled out, while individuals with a strong FDB will have no problem maintaining the card underneath their toes.
In addition to weak FDB, other causes of plantar fasciitis include: repeated hill workouts, tight calves, foot mechanics, and occupational factors to name a few and must be addressed during treatment. Treatment for plantar fasciitis should focus on improving strength of the tiny foot muscles to help support the plantar fascia, stretch calves, and reduce occupational risk factors. As well as having manual therapy performed to help achieve quicker relief. Research shows when manual therapy is combined with stretching it is superior in short term outcomes over just stretching. At TROSS we use many manual therapies such as: ART, FAKTR, and dry needling to help stimulate the healing process and get you back to doing what you love.
Weak FDB is not often talked about when individuals hear about causes of plantar fasciitis, but its role in the prevention and treatment of plantar fasciitis is vital. If you have any questions or would like to learn more contact TROSS today for a free consultation! TROSS proudly serves the Cottleville, St. Peters, St. Charles, O’Fallon, and St. Louis communities!
- DeMaio M, Paine R, Mangine RE, Drez DJr. Plantar fasciitis. Orthopedics 1993; 16:1153-1163.
- Abreu M, Chung C, Mendes L, et al. Plantar calcaneal enthesophytes: new observations regarding sites of origin based on radiographic, MR imaging, anatomic, and paleopathologic analysis. Skeletal Radiol. 2003;32:13-21.
- Menz H, Zammit G, Munteanu S, Scott G. Plantarflexion strength of the toes: age and gender differences and evaluation of a clinical screening test. Foot Ankle Int. 2006; 27:1103-1108.
- Renan-Ordine R, Alburquerque-Sendin F, Rodrigues De Souza D, et al. Effectiveness of myofascial trigger point manual therapy combined with a self-stretching protocol for the management of plantar heel pain: a randomized controlled trial. J Orthop Sports Phys Ther. 2011;41:43.