B-L Solution is a natural pain reliever. You could give that to him on a regular basis. It comes in liquid and pellet form. You would have to guesstimate the dosage for him from the horse dosage and just play around with it to get a dosage that works for him.
you need a red top tube of blood and send to washington state. it is a total of 19.50 for one test 9,50 a test after that. they will bill you. but it will cost you alot more than 19.50 if you spread cae to your herd, or someone elses. how old is he?
Is it both knees? What is his feed? Some goats grow faster than they can supply the correct nutrients to their body. Basically the bones grow to fast and it causes swelling the joints that aren't quite ready for it. They eventually catch up and it goes away.
If its one then like someone else said it could be an injury. Is it hard or soft? Tender to the touch? Abnormally hot?