The plantar fascia is the tissue that runs along the bottom of your foot from the heel to the toes. Plantar fasciitis is simply when this tissue is inflamed and irritated. After prolonged irritation it is also possible to develop a bone spur on the heel.
When the fascia is strained, it usually becomes painful where the fascia is attached to the heel-bone. The heel hurts when walking, running, or even standing. It also hurts when the sole of your foot is stretched, for instance if you pull your foot and toes backwards towards you with your hands.
Some causes of plantar fasciitis include:
John Hopkins - Patients Guide to Plantar Fasciitis
Planterfasciitis.net - Definition and cause of plantar fasciitis and treatment products
Plantar Fasciitis - Treatment products from Roadrunnersports.com
Black toe nails, a common condition for runners, and high mileage walkers, is caused by injury to the tissue under the toe nail. Friction is the cause of most black nails. Friction from tight shoes, sudden stops and starts that jam the toe against the front of the shoe, or down hill walking that causes the foot to slide forward in your shoe.
As a result, the toe repeatedly hits the end of the shoe, causing bleeding, fluid build up, and bruising under the toenail. In some cases the nail will discolor, with little or no pain. It is best to alleviate the problem and leave the nail alone. In most cases the nail will eventually fall off and regrow without any significant deformity.
Friction can be caused by any of the following:
When to see a doctor:
If enough pressure builds beneath the nail, it can become quite painful, requiring your physician to drill a hole into the nail to relieve the pressure.
You notice any redness that might be associated with an infection.
MORE FOOT PROBLEMS, INFORMATION, AND HELP
Morton's neuroma - See this link for information
Dr. Kiper - Sports medicine with emphasis on stretching. Includes "dynamic" stretching of the foot, plus healing and prevention of biomechanical injuries with custom fluid orthotics.
Sole Custom Footbeds - Custom fit your shoes with custom molded insoles.