public SixDofJoint getJoint(String boneName) {
        PhysicsBoneLink link = boneLinks.get(boneName);
        if (link != null) {
            return link.joint;
        } else {
            logger.log(Level.WARNING, "Not joint was found for bone {0}. make sure you call spatial.addControl(ragdoll) before setting joints limit", boneName);
            return null;
        }
    }
Return the joint between the specified bone and its parent. This return
null if it's invoked before adding the control to a spatial

@param boneName the name of the bone
@return the joint between the given bone and its parent
jme3-jbullet/src/main/java/com/jme3/bullet/control/KinematicRagdollControl.java