Thanks so much for the answers to my questions.
There are several possible explanations for the problems with his back legs, especially if one seems more affected than the other:
1. I'm certain that he has arthritis in either his hips or knees (or both), given his age and since he's part-lab. He could have had this condition for awhile and exacerbated it if he fell or twisted/torqued his body in a certain way.
2. A problem with the spine such that compression of the cord secondary to a mass or disc might also explain his symptoms. This might be a little more difficult to diagnose although a good physical exam should detect neurologic deficits.
An x-ray might reveal narrowing of the disc spaces but often an MRI is needed to diagnosis this problem.
3. I've seen some dogs with tick diseases suddenly have problems with their back legs and their gait. Usually these dogs are running fevers although not all of them do. If you wanted to take his temperature, normal is between 100 and 102.5.
We do have tests for many of these diseases, but we are testing for antibodies, not the organism itself, in most cases. If antibodies are not being produced (for whatever reason) then the tests could be negative and yet this is still the underlying problem.
I've also come to believe that there are tick diseases that we haven't even been able to identify yet and thus would not have tests for all of them.
Tetracycline-based drugs are the treatment for many tick diseases that we see but would have to be dispensed by your vet.
Regardless of the underlying cause, since he's not currently taking any medication, you could give him Aspirin at a dose of 10 mg/lb twice a day, with food to avoid stomach upset. For example, if he weighs about 50 lbs, then his dose would be 1.5 of the full strength, 325 mg tablets at one time.
This drug has anti-inflammatory as well as anti-pain properties which could help in this situation. My only reservation about recommending it's use is that it might interfere with what your vet would want to prescribe if you have to have him seen, but several doses should cause no harm.
While supplements won't help him now (for the short term), then may help with any arthritis issues in the long run.
1. I'm a huge fan of joint supplements which contain glucosamine and chondrotin sulfate such as Dasaquin or Cosequin which are veterinary products specifically formulated for dogs. Quality control is a big problem with these products since what’s on the label is not necessarily what’s in the bottle which is why I mentioned specific brands. These are available on the internet.
2. Also, fish oil supplements can be helpful since they have anti-inflammatory properties. Welactin and 3V Derm Caps are good veterinary products and are also available on the internet. It takes several weeks for these products to build up in the system, so you might not see immediate results. But once started, these supplements should be continued for them to be effective; you wouldn't stop and start them, in other words, like you would drugs...but you may already know this.
3. Another option would be Zeel which is a human combination homeopathic that can be used in conjunction with other NSAID medications and has a very low incidence of adverse effects Dose would be one tablet two to three times a day....I'd go with three times a day for the first 2 weeks, then drop back to twice a day for maintenance.
4. Alternative therapies such as hydrotherapy, laser therapy, massage therapy and even acupuncture have been shown to be very useful for chronic joint and spine problems.
I hope this helps and that he's feeling better soon. Deb