The larger of the two bones in the lower limb. One surface of the tibia lies immediately beneath the skin in front, forming the shin; fractures of this bone are usually compound ones. The thigh bone abuts on the larger upper end of the tibia at the knee-joint, whilst below, the tibia and fibula together enter into the ankle-joint, the two bosses or malleoli at the ankle belonging, the inner to the tibia, the outer to the fibula.