Really not sure what to do with Obi now (4 month old ACD), he has been limping on and off -mainly on - for about a month now, Vet can't find anything on a physical exam, no sign of pain, other than the lameness, he would be happy to carry on like a normal mad puppy if we let him, but he has had reduced exercise, mainly on lead, is kept in the carpeted living room so he cannot slide on the wooden/tiled floors, he has started hydrotherapy (was planning this anyway) and is on a puppy/growing formula of glucosamine (Synoquin) to be on the safe side. 
Really not sure about having X Rays done at his tender age but may have to soon if there is no dramatic improvement.  I don't think it can be OCD (not prevalent in our breed) as there is no pain on exam, maybe Pano as the lameness occasionally "shifts", I suppose it couldbe a badly bruised bone, or tendon injury but would have expected those to have sorted by now.
Sorry to ramble, but cannot believe our luck, my older dog had to stop doing agility after a leg injury which took ages to diagnose and I really can't face going down that road again! 
Anyone any thoughts on what could be causing the lameness???
Hayley

Pano is possible but 3 months is young to start, have you spoken to the pups breeder about it? My pup is suffering intermittent lameness but it did not start till 4 + months and the onset was accompanied with a bout of diarrhoea, so I put it down to pano, but at 3 months I doubt it is. If you are worried have the pup x-rayed and put your mind at rest.

Hi,why not have him xrayed to put your mind at rest! i wasnt happy with my collies hind movement so had his hips xrayed at 8months & with hydrotherpy & supplements hes now sound,maybe if i hadnt been sure what it was he would be alot worse now!

I'm sure we will get him X Rayed this week if he is no better, hopefully they will do it under sedation like they did my older dog as I am really worried about him having a GA.
Jackie - I have spoken to the breeder, there are no problems in the breed that could be causing it (she is one of the top people in the breed so I am confident that she is right) though of course there are many conditions that can affect any dog.  Is diarroeah connected to Pano?  Obi has had this intermittently during the last month too.
Someone else in Cattle Dogs suggested that a too high level of protein could cause lameness and growing problems, but Obi is on puppy NatureDiet which is only 12% protein so don't see how that could be causing any problems
Thanks for your comments, it is such a shame for such an active pup, with excellent potential working ability to be having these sorts of problems - especially as he has already had two possible stud requests!!! Bless him, he hasn't even dropped yet!
Hayley

i hope hes ok , i really feel for you , because my lovely boy flynn has got bad hips. we do obedience & hes going to be (&is) very special! hes incredibly handsome & talented. i was gutted when i learned about his hips.(all his parents Gprand parents have low scores& he was never overfed/underfeed or over exercised!)so i know how you feel! if  there is something wrong, well here is what i felt about flynn; i wouldnt swap him & it makes him xtra special!
ggod luck mate! you can always do obedience!!!!

Thanks Michelle, sorry to hear about Flynn's hips, it must have been a real disappointment, especially when you did all the right things!  Obi is definitely very special, and yes I will stick to Obedience if that is all we can do - I have started on that path anyway but I love agility and was hoping to try working trials too, but well, that's life!  What breed is Flynn?
Hayley

Hi Hayley,
Our beagle went through a few weeks of limping. We don't know what happened to her but can only assume that it happened when playing with our other dog.
She was 5 months when it happened and i was really worried and thought it may be something serious. Ruby limped for approx 4 or 5 weeks. It can be so easy for a puppy to go lame but so hard to let it get better as they don't know when to stop and rest. The vet said the only thing that would improve it is to make her rest, which is easier said than done with a puppy. We restricted her exercise and i discouraged her from charging around by playing with a toy with her.
If i were you i wouldn't take him for walks at all for the time being and i would try to keep him as quiet as possible. It took Ruby a couple of weeks of proper rest until she improved.
I hope you find out what is wrong and i hope its nothing serious. Keep us posted.