One of my guinea pigs started limping this evening. He's not been in top form for a while now and I suspected the kidney problems that took his brother (he pees a lot, smells a bit pissy, drinks a lot, but is otherwise very happy). He's never been the Usain Bolt of guinea pigs, always preferring to sit still eat, wander a short distance and see if he can pee on your trousers, sit in the puddle of piddle, wander off again, etc.
While we were eating tea this evening, I noticed him sitting even more still than usual, at a slight list (like a narrowboat that needs the ballast rearranging slightly). Then when I gave them their tea, he kind of hobbled out. I picked him up and examined him. No obvious signs of damage, nothing I can think he injured himself on, but he is slightly noisy with his breathing. (Only slightly and it may have been him talking - he has quite a repertoire of sounds.)
He's eating OK and his hutchmate seems unconcerned. They get on well and I have never seen them fight. He does sometimes get the other one trying to hump him, or using him as a step-up to the roof of their wooden house, but he's never before sustained any injuries from this - just developed a 'slightly annoyed' expression.
Any advice?