Ponyup: This same thing happened with my dog back home in Connecticut, and it turned out to be Lyme disease. Don't want to alarm you, but just wanted to share my experience.
Taken from
here
"...symptoms of Lyme disease that may include limping, usually one of its front legs, fever as high as 105 degrees, fatigue, appetite loss, and signs of discomfort or pain"
Hope your Logan feels better!