"All things in moderation."
Our 5 mo old Golden male has "growing pains" as well but it's not enough to slow him down. Rx - Lots of quiet time, play is supervised - the 5 year old thinks he's still a puppy too - and limited to a few minutes. Long walks on lead get him the exercise he needs while also getting good heel and leash training. No more than 2 or 3 marks on land but as many water marks as he can handle. The rest of the time is in training mode under leash control. While some free time is good for the pup this is the time to ensure he understands that you set the rules and "easy" or "sit" mean what you say. You can make a good training routine by allowing some free for all but calling for the time-out and enforcing it. Do some heel or fetch drills and then give him a play break for a few minutes. The panoteitis itself should not be a long term problem but could result in other soft tissue injury as pup over-compensates or crashes due to the sore leg. Been there. Good luck and hope you have long ride with the pup.