My name is ***** ***** I’ve been involved professionally with dogs in the health and behavioral fields for over 18 years. It will be my pleasure to work with you today.
Dogs who will not put weight on a leg could have a dislocated hip, or knee injury such as an ACL tear. You can read about dislocated hips here:
And read about ACL injuries here:
Often with an acl injury you can move the leg without the dog appearing to have much of a problem with you moving it, but it becomes very painful when they attempt to move the leg. Since he is not putting weight on it, it probably is NOT a pulled muscle. I would have him seen by your vet as soon as possible.. If possible, contain him in a crate until you can get him seen. If it is a dislocated joint it is best addressed as quickly as possible. In addtion, buffered aspirin can be given to a dog with a dosage of up to 5 mg per pound every 12 hours. Keep in mind that a dog's body does not metabolize aspirin in the same way as a human and thus should not be given more than a day or two without contacting your Vet. The aspirin may need to clear your dog’s system before other medications can be given, so keep that in mind if you decide to give aspirin and be sure and tell your vet when your dog is seen. Read side effects and precautions here.
If aspirin is used, your vet may not be able to prescribe other drugs until it clears from your dog's system. I'd probably hold off on the aspirin since he will be seen tomorrow. About the only thing you can do apply cool compresses to the leg for 5 minute intervals. 5 on and 5 off to ensure the tissue does not get too cold. I'd also limit all activity and crate if possible only allowing him out to eliminate and have him on a leash for that.
Now if he was putting the leg on the ground, then it might just be a pulled muscle and crate rest would be helpful. You want to avoid having him use it at all and that include him holding it up until he is seen by your vet. Keeping him inactive is going to be important and I'm sure your vet is going to recommend it as well even if he prescribes an antiinflammatory medication that makes your dog feel a lot better. The inactivity allows the injury time to heal and if he is moving around, he might reinjure the area. So be sure to ask the vet if he doesn't recommend it.
I hope this information is helpful to you. If you would like any additional information or have more questions please don’t hesitate to press the reply to expert or continue conversation button so I can address any issues you still have . If you do find this helpful, please take this opportunity to rate my answer positively so I am compensated for my time.