Which bones have a growth plate at the proximal end?

• A. Cannon bone
• B. Long and short pastern
• C. Proximal phalanx
• D. Distal phalanx

Answer: (B)

Growth plates are cartilage regions at the ends of long bones where lengthwise growth occurs during development; they close as the animal reaches maturity.

In the horse’s limb, the long pastern and the short pastern are the proximal and middle phalanges of the digit. These two bones retain open growth plates at their proximal ends while the horse is growing, so they have a growth plate located there. The cannon bone (the metacarpal) is a fused limb bone whose growth is not defined by a proximal physes in the same way, and the proximal phalanx and distal phalanx have growth activity positioned differently (not specifically at their proximal ends in this context). Therefore, the bones with a growth plate at the proximal end are the long and short pastern bones.