The plantar fascia is the tissue that runs along the bottom of your foot and connects your heel to your toes. Inflammation of this tissue can be gradual and quickly become chronic. Athletes—particularly runners—and anyone who spends a lot of time standing are among the most susceptible to this injury. The repeated stress on the plantar fascia causes small tears in the tissue, which results in severe heel pain. Those who suffer from plantar fasciitis describe what feels like a severe bruise on the heel and difficulty walking, especially first thing in the morning or after sitting for long periods of time.