Sprains in dogs
Dogs can become lame for many reasons. If your dog suddenly starts limping a little after playing but without the joint being swollen, you can probably wait.
If your dog has swelling over a joint or does not load the leg at all, you should contact a vet. A young growing dog with sudden lameness should always be examined quickly by a veterinarian.
Have a feel around your dogs limbs
Feel and inspect the dog's paw. Does it hurt, do you see wounds? Bend and stretch your dog's joints. Does it hurt? Do any joints feel swollen? It is not unusual for pet owners to think that the paw is the problem when a dog is lame when in fact it may be a joint higher up that is the problem. Is there a wound somewhere that hurts?
Give your dog time to rest
A dog with a limp should rest properly and not strain the leg. Only go for short leash walks and don't let them play with other dogs. A clear improvement in the lameness should be seen every day.
When should I contact the vet?
Contact a veterinarian if the dog has not improved after a couple of days, if the lameness disappears with rest but returns after movement, if the joint swells, if it hurts when you touch the joint or if the dog does not walk on the leg at all.