I have a German Shepherd who just turned 10 years old in June. I noticed last Saturday he had a hard time jumping up on the bed to come sit beside me, which is something he would be able to do flawlessly before so I gave him a boost up. Since then I have noticed he can’t walk fast anymore and is having a hard time getting up to walk. He has a decreased appetite but is still drinking water as normal. He is sitting to eat and drink and is walking slow with his back hind legs, I’ve seen him misbalance and fall forward with his hind legs giving out. Other than that I have rubbed his legs and back and no yelps in pain but he seems uncomfortable. Is this a result of old age?