In early March, after a collision with Jessie Max started limping and wouldn't weight bear on his left leg.
We tried to let it run its course, there was no pain when articulated and it seemed to all intent and purposes to be a soft tissue injury.
After a couple of days the limp was getting no better, so we took him to the vets. The vet concurred our thoughts and prescribed a course of Meloxidyl anti-inflammatory suspension. Within 12 hours of taking, Max developed diarrhea with traces of blood. We naturally rang the vet and she advised no more medicine to see how things settled.
The following day the limp seemed to have gone and his stomach returned to normal.
Unfortunately after another day, he would not put weight on his leg again. 
After a call to the vet she suggested retrying the Meloxidyl. Although it may of been the cause of his upset stomach it had eased the leg. This proved to be a big mistake.

Over the next 3 - 4 days Max became very ill. Even though we had only given him one dose after the advice to retake, it seemed his stomach had not fully recovered from the first dose. The days became long with him needing to toilet every hour, day and night. He was really good and didn't have a single accident in the house. But it wore him (and us) out. Within those days we had a couple of contacts with the vets, the last to administer injections to try and stop the sickness and diarrhea. Fortunately after 4 days, that seemed like a month, he was back to normal but had lost nearly a Kg in weight. 
On the plus side, all the inactivity must have helped as he was no longer limping.

We posted this 15th March on Facebook
Thinking all was well, we slowly started building him back up with food and exercise. All was fine for about 2 weeks, then for no apparent reason he developed a limp in his right leg! Back to the vets. This time we saw a different member of the team who could again could feel no muscular or bone related reason, so prescribed anti-inflammatory tablets, as you can imagine we insisted on a different type, Carprodyl. 
These worked miracles and although he had a weeks course the limp stopped in 24 hours.

Following  yet another occurrence but back to the left leg, the vet suggested the next step would be to take some X-rays. As he was booked in for castration and X-rays require heavy sedation we agreed we would do some while he was out of it! Of course while we waited for the decided date he didn't limp once!

On the10th of April Max had his boy op and a series of front leg X-rays. 
The result, nothing abnormal showed, all joints seemed good.

Relieved we decided to continue building up his stamina. 
By the end of may there was no problems and he was coping with walking and running off lead fine.

On evening early June Max started limping on his right leg, wouldn't weight bear. By the next morning all was well. The following week he started limping on his left leg this again was only for 24 hours.
After this second occurrence we decided to go back to the vet. This time ensuring we saw the senior practice owner. The vet was very good and manipulated all the joints. His conclusion is probably one only an older very experienced vet would offer. Its puppy growing limps. Joints not fully formed allow for occasional pulls on muscles and ligaments. No point rushing to pay for more tests. In his experience he would grow out by 13-14 months of age.

He was very reassuring and suggested that there could be a small chance of a loose piece of cartilage impinging, but given the clear X-rays and alternating legs, loose joints was the most obvious cause.

At the time of writing we have been given a small supply of Carprodyl to have in, so we can treat straight away if it happens again. 

WHICH is the BAD LEG? its obvious if they hold the paw up but not as easy to tell if they are walking!

If only one forelimb is involved, the head and neck move upward when the affected limb is placed on the ground and drops when the unaffected limb bears weight. 
So in the above video max has a RIGHT leg limp.