A less-kind explanation is that ankles become enlarged because of sprains due to uncoordinated trail runners. Knees scarred from falls or surgery are great for avant-garde fashion magazines. Marathoners and ultramarathoners have enlarged elbows from using them as weapons to protect themselves in the first mile of a crowded race. Neck muscles become oversized due to constantly turning the head to see who is behind you. Sprinters have enlarged temple veins, not due to exerting themselves over a short distance but due to scowling fiercely at their competitors.
Same reason goes for permanently wrinkled foreheads.
Ultrarunners do not have to worry about this, since they are ultra-cool. Trail runners have enlarged pupils because the pupils expand to gather as much light as possible in the shaded forest. That is why runners look like Dondi when emerging from the woods. If they run too long in the woods, they look more like Little Orphan Annie. Sprinters are not affected since they always wear rad sunglasses.