Pronation means to rotate (the hand or forearm) so that the surface of the palm is downward or toward the back; or in the foot to turn the sole of the foot outward so that the inner edge of the foot bears the weight when standing.  In the foot, if someone “over-pronates” they are more flat footed.  This can lead to foot pain as well as knee pain, shin splints, achilles tendinitis, posterior tibial tendinitis, Piriformis syndrome, and plantar fasciitis.