Chronic foot, leg and knee pain during running can be caused by the foot hitting the ground with excessive force and excessive rolling in of the feet after they hit the ground. These problems can often be alleviated just by:
• taking shorter strides to reduce the force of the foot hitting the ground (Scan J Med & Sci in Sports and Ex, May 30, 2018), and
• putting special inserts called orthotics in your shoes (JAMA, 2020;323(18):1802-1812).

Orthotics
People with high arches are at increased risk for recurrent foot and leg pain, and even stress fractures of bones of their feet, because their feet are usually very poor shock absorbers (Curr Opin Rheumatol, Mar 2011;23(2):148–155). When you walk fast or run, your foot hits the ground with great force. For example, when you run at six miles per hour, your feet strike the ground with a force equal to about three times body weight. This force can break bones and damage muscles, nerves, and tendons. Most people land on the outside bottom of their feet and roll inward. This is called pronation. The rolling inward of the foot helps to prevent injuries by absorbing some of the shock of the foot striking the ground. Some people are at high risk for injury because they have very stiff ankles that prevent their feet from rolling in normally, and their feet strike the ground with greater force. These people usually have normally-formed arches and only appear to have high arches because their feet do not roll inward as far as they should. These are the people who often benefit from orthotics (Cochrane Database of Syst Reviews, October 2007).

Orthotics are special custom arch supports that help to absorb shock and prevent foot pain. Orthotics can often help reduce pain and discomfort by lowering the force on the bottom of the foot called the plantar fascia (Scientific Reports, Feb 8, 2019;9(1688)). Most running shoes today are fitted with shoe inserts that are similar to custom orthotics, which can reduce foot-strike force to help prevent injuries. If pain and injuries persist, a podiatrist will use either a 3D scanner or plaster molds of your feet so their orthotics lab can create inserts that address your exact foot issues.

Decreasing Foot-Strike Force
Eighty percent of long-distance runners suffer injuries that force them to take time off from running each year (Br J Sports Med, Aug 2007;41(8):469-80). Most wear-and-tear running injuries are caused by the high impact of your foot hitting the ground, which is determined most by the length of a person’s natural stride (Scan J Med & Sci in Sports, May 30, 2018). The runners most likely to be able to continue to run as they age are the ones who take shorter strides (Med Sci Sports Exerc, Jan 2016;48(1):98-106). You take shorter strides by never fully straightening your knees. To convince yourself, place your hands on the huge quad muscles in the front of your upper leg while you run. Each time your foot strikes the ground, you will feel the muscles shake like jelly. This force is transmitted up your legs to your hips and back, and done repetitively, it can cause injuries (Br J Sports Med, Apr 2016;50(8):450-7).

Runners who are injured frequently are likely to benefit most by shortening their strides, which then coincidentally increases likelihood of their landing on the front part of their feet, rather than on their heels. Contrary to common belief, it is not important whether you land on the front of your foot or the heel. However, the more you overstride, the more likely you are to land on your heel. Landing on the front of your foot does not prevent injuries, it is only a marker that you are not overstriding. A study of the 2017 IAAF World Championships showed that 54 percent of the men and 67 percent of women landed on their heels (Journal of Biomechanics, May 22, 2019). As runners start to feel tired, they naturally shorten their strides and this decreases the force of their foot striking the ground (Med Sci Sports Exerc, Dec 1999;31(12):1828-33). The bent-knee, shorter-stride lessens the force of their heel striking the ground and places it forward to the area behind the big toe.

My Recommendations
If you suffer from chronic or repeated foot, leg or knee pain, particularly when you try to exercise, you should check with your doctor or a podiatrist to see if you have:
• feet that appear to be flat because they are already maximally pronated and cannot roll inward enough to reduce the shock of your foot hitting the ground, or they have a high arch that prevents them from pronating, causing more force to enter the foot
• over-striding that markedly increases the impact force of your foot hitting the ground when you run
Many people who suffer recurrent running injuries can be helped by placing custom orthotics in their shoes and by taking shorter strides so they never fully straighten their knees when they run.

Note: My son, Gene Mirkin, DPM contributed to this report.
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