Yellow Lab: Was limping on one front leg, now the other.?

About a week ago, my 5 1/2 year old 90lb. yellow lab was totally fine. My wife and I decided to take the dog for a walk (which we usually do 3-4 times a week). Somehow from the door to the road (40 feet), my dog started limping. His left front left was the problem. So, we canceled the walk. We let the dog rest and after a four days or so he was fine. Today, we went for another walk, and he started limping about 1/2 mile into the walk. But, this time it's his right front leg. I don't know what going on. Any ideas? He doesn't act like he's in pain, although, he's never really shown pain before.He is just slightly overweight. We live very healthy lifestyles and feed him good food. He never bites his paws/nails. As for the Lyme Disease: I'm not sure that's a great explanation. This just happened all of the sudden. It's almost like he sprained his ankle, twice, which seems odd.We live in El Paso, TX. I'm not sure if this is an area that commonly has ticks or Lyme disease. This is the desert.

1) Your dogs nail, must be trimmed, or there's something under the foot. Is your dog always licking or chewing on his/her foot?2) Is your dog overweight and having a hard time walking?3) If these two symptoms don't pertain to your dog, take your dog to your vet

Is he overweight for his size? Is he protected from lyme disease? Lyme disease would show more stiffness than anything. But labs are a breed to get arthritic...you can try a supplement and if he doesn't improve or gets worse take him to a vet soon...even if he doesn't seem like he's in pain, he probably is! We'd go to the doctor if we were limping around, even sporadically!

Have him tested for tick borne disease, if that's likely where you live . Lyme disease can cause shifting lameness most often in front legs. He's a little old for panosteitis. Whatever the reason, it's worth a vet visit.