If you try aspirin...check with your vet first. It has to be buffered aspirin. It doesn't work as well as doggie anti-inflammatory meds would work because buffered aspirin isn't processed through the kidneys as well.
Actually, the reason you would prefer a prescription anti-inflammatory over aspirin is the effects on the gut, stomach specifically. Aspirin is a nonselective COX inhibitor. It inhibits both the "good" COX-1 enzyme as well as the "bad" COX-2 enzyme. The inhibition of COX-2 helps reduce inflammation. But the inhibition of COX-1 can cause
gastric ulceration, platelet dysfunction and decreased renal perfusion. Most newer prescription anti-inflammatory available at your vet inhibits the COX-2 while sparing the COX-1. This causes fewer side effects.
In layman's terms:
Can you use aspirin? Yes, but be aware that you are at in increased risk of the above mentioned side effects. Like Barb said, it needs to be buffered and given with food. Also, never use two different anti-inflammatory at the same time (i.e. a prescription one and aspirin). Some anti-inflammatories work better than others in certain dogs. So when one stops working there are others to try.
Our vet recommended over the counter Glucosamine & Chondroitin.
Good choice to add to the anti-inflammatory. Unfortunately some are better in quality than others. There is no regulation for the over the counter ones. Of course, the ones you get from your vet are of higher quality but they can be downright expensive. Over the counter products are good if you can find a good quality one. I've been told by a pain specialist that Osteo Bi-Flex is a good product to try.
One thing you might want to consider. Obesity is strongly associated with the development of Osteoarthritis (OA). If your animal is overweight (as a lot of Labs are), a restricted diet and daily exercise can significantly reduce the effects of OA.
Disclaimer: While I'm a veterinarian in real life, I don't play one on TV. Every animal is different and you really should consult your regular veterinarian before starting any new medication or diet on your pet.