12 yr old lab cant stand today

Question
My 12 year-old, 85 pound, male, neutered lab is having trouble standing today. No other symptoms but he can't seem to get his back legs under him. Is this something I should get him to the vet right away for? Any info is appreciated!
Thanks!

Answer
Yes see the vet.  We were ready to put our 14 year old to sleep last week, but the vet suggested a different pain killer and she is doing much better.  

Be careful of his weight.  Every extra pound is bad.  Evaluate the dog as illustrated in this link, http://www.longliveyourdog.com/twoplus/RateYourDog.aspx You may want the vet to confirm your judgment. Adjust the dogs food and exercise as needed to reach its ideal body condition.