OOP Constructors as Parameters

I would build things from the bottom up:

#include "Joint.h"

Joint LeftHip(0);
Joint LeftKnee(1);
Joint LeftAnkle(2);
Joint RightHip(3);
Joint RightKnee(4);
Joint RightAnkle(5);

#inlcude "Leg.h"

Leg LeftLeg(LeftHip, LeftKnee, LeftAnkle);
Leg RightLeg(RightHip, RightKnee, RightAnkle);

#include "Body.h"

Body body(LeftLeg, RightLeg);