Our yelow labrador cross golden retriever (12.5) has been taking green lipped mussell. We have noticed a difference in that she doesn't groan as much as she did previously, when she lies down.
It took about 4 weeks or so to make a difference, but interestingly when the tub ran out, we were a bit busy and neglected to buy another straight away. After a week or so without it, she started groaning again. Again it took the 4 weeks back on the tabs for her to stop. Pretty sure it works. Think it is called vetri-flex, available from viovet.