Dog slows down in cold weather — is it joint pain?

Cold-weather slowing is one of the clearest signs that joint pain is a factor — synovial fluid becomes more viscous in cold temperatures and inflamed joints respond more acutely to the chill. The fact that it's weather-correlated rather than constant suggests you're in the early-to-moderate range rather than advanced arthritis. Does he warm up back to normal once he's been moving, or is the slowness present throughout a cold day?

The summer-winter contrast is the arthritis talking. That pattern — fine in warm weather, reluctant in cold, improves once moving — is textbook mild-to-moderate osteoarthritis in a large senior breed. It's worth treating now rather than letting the seasonal pattern become year-round. Start him on YuMOVE Senior — the anti-inflammatory and joint lubrication support from the green-lipped mussel extract directly addresses the cold-weather exacerbation. You should notice the cold-morning resistance reducing within 6–8 weeks. It won't make him love January, but it should take the edge off considerably.