Have you stepped out of bed first thing in the morning and felt like you’re walking on glass? If so, then you’ve likely dealt with plantar fasciitis. The plantar fascia is a tough band of connective tissue that runs underneath your foot connecting the base of the toes with the heel bone. To understand the function of the plantar fascia, we need an understanding of our feet.  

 Each foot has 28 bones, 30 joints, over 20 muscles, and four arches! The most noticeable arch in the foot is the, medial longitudinal arch. This arch is the primary loadbearing and shock-absorbing structure of the foot. It is supported by both passive (plantar fascia and ligaments) and dynamic (muscles) structures. 

 Two of the primary functions of our foot is to absorb shock and push off the ground with every step we take! The foot needs to be both pliable and rigid to accomplish these tasks. 

Let’s talk through what happens in the foot with each step: 

1. When the foot first touches the ground, the forefoot and rearfoot are “unlocked” and the plantar fascia gives way to allow the arch to collapse and adapt to different surfaces 

2. When the foot is about to leave the ground, the forefoot and rearfoot “lock” and as your heel rises off the ground and your toes bend, the plantar fascia tightens to elevate the arch and become a rigid lever for forward propulsion. This is known as the “windlass mechanism.” 

If when the foot touches the ground, you have a faulty flexor hallucis brevis muscle (muscle that flexes your big toe) that is unable to stabilize the arch, increased strain is placed on the plantar fascia. This can contribute to plantar fasciitis. 

 During static standing, the foot is adequately supported by the medial arch and other passive structures. But when we increase the demand on our foot with walking, running, or jumping, then we need a second line of support. Cue in muscles.  

Muscles are designed to absorb shock. When the muscles around the plantar fascia fail to do their job, more stress is placed on the plantar fascia, which contributes to pain. 

 Muscles can be “failing” for several reasons. Two things to consider are 1) Is the muscle tight and bound up? 2) Is the muscle weak? 

 If the muscles are tight or weak, they cannot properly absorb shock and again, increased stress is placed on surrounding joints, bones, ligaments, tendons, and fascia. 

This is only one factor to consider when identifying the cause of plantar fasciitis. During our next blog, we will be discussing why this is a chronic, nagging injury and other potential risk factors. 

References:

Dicharry, J., (2012) Anatomy for Runners: Unlocking your Athletic Potential for Health, Speed, and Injury Prevention. Skyhorse Publishing. NY. 113-116. 

Mckeon, P. O., Hertel, J., Bramble, D., & Davis, I. (2014). The foot core system: a new paradigm for understanding intrinsic foot muscle function. British Journal of Sports Medicine, 49(5), 290–290. doi: 10.1136/bjsports-2013-092690

 Miller, L., & Latt, D. (2015). Chronic plantar fasciitis is mediated by local hemodynamics: Implications for emerging therapies. North American Journal of Medical Sciences, 7(1), 1. doi: 10.4103/1947-2714.150080

 Neumann, D. (2017). Kinesiology of the musculoskeletal system: foundations for rehabilitation. St. Louis, MO: Elsevier.593-594. 

 Plantar Fasciitis https://www.physio-pedia.com/Plantar_Fasciitis