Tibia
the shin bone, with the exception of the femur, the longest bone in the skeleton. It is the anterior and inner of the two bones of the leg, and alone communicates the weight of the trunk to the foot. It is slightly twisted, and articulates with the femur, fibula, and astragalus. Its superior extremity is thick and expanded, with two condylar surfaces supporting the femur, and an external and an internal tuberosity; the shaft is three-sided, the inner surface convex and subcutaneous; the inferior is smaller than the superior extremity, and forms a thick process called the internal malleolus. The tibia corresponds with the radius of the arm. In entomology, the fourth joint of the leg. In music, a kind of pipe, a common musical instrument among the Greeks and Romans. It had holes at proper intervals, and was furnished with a mouthpiece.