ulna/radius tibia/fibula

Q: I was wondering how to distinguish the difference between ulna and radius and between tibia and fibula?

A: For our purposes, lets just say the ulna is closer to the higher digits (4 and 5) and it projects to form the elbow protrusion. It is also broader proximally and narrower distally. The radius tends to be smaller and closer to the lower digits (1 and 2). For the hindlimb, just go with the tibia is bigger than the fibula.