Calf Not Putting Pressure on Leg

So I have an approximately 7-8 week on Holstein bull calf that we are weaning. He is not running fever and appears not to be dehydrated. We are feeding a 12% protein pellet once in the morning and access to hay all day long. He is acting lively and is able to stand. His eyes look bright and he appears healthy. Only thing is he wont put pressure on his front right leg. After close inspection I do not note anything obviously abnormal. His hooves look good. He doesn't seem to wince or try to pull away when I manipulate it. There "might" be some very very slight swelling to the knee on that side but you really have to look VERY hard to see it. And I may just be making that up because I want find something wrong. His poop is firm, not loose. He is breathing normally and no discharge from his nose.

He acts happy and healthy except he wont put pressure on that one leg. I have him in a stall in the barn hoping he just sprained it but he seems to be getting worse. It started out with a limp and had progressed to not putting any pressure on that leg. I am curious if I should treat, and how I should treat it. I have Penicillin on hand but I do not think it is an infection. Any thoughts would be appreciated!