oppoite+convey When+the+Concave+surface+is+moving+on+the Concave+surface,+the+joint+GLIDES+in+the SAME+direction+as+the+bone+MOVES When+the+Convex+surface+is+moving+on+the Concave+surface,+the+join+GLIDES+in+the OPPOSITE+direction+as+the+bone+MOVES Examples