As your foot bears weight, your arch flattens, stretching the plantar fascia. Repeated flattening can inflame your plantar fascia. Repeated flattening can inflame your plantar fascia or tendons, break down joints, or weaken muscles. Wearing shoes with weak arch support or a worn-out midsole can make matters worse. Other contributing factors include flat feet, which can overstretch your plantar fascia; abnormal leg length, which causes the foot of your longer leg to flatten too much; being overweight; and running on hard or uneven surfaces.
With repeated up and down pounding, the pressure on your foot is concentrated on the ball of your foot, rather than spread over the entire foot. Your foot's tendons and muscles aren't able to absorb the extra stress coming up through your bones, so fractures or tendon injuries in your foot, ankle and calf can occur more easily. Being overweight increases the pressure, as does jumping on hard surfaces, over training or wearing stiff shoes or ones lacking support in the front.
When you make sudden sideways movements, your "tripod" of bones, your heal and first and fifth metatarsals, is thrown off balance. Because your joints are forced beyond their normal range of motion, ligaments and joints can be injured. Playing on an uneven surface is a set-up for this type of injury, as is wearing shoes with loose ankle support, worn our or the wrong size Other contributing factors include weak ankles, high arches, or fatigue.