For what it is worth, mycoplasma synovitis (MS) is a bacterial infection, not a virus. I don’t think that this looks like it, but I could be wrong. MS usually affects both ankles and hock joints causing swelling and infection of the joints.
Sorry about that misinformation. My brain misfired and I was confusing MG with infectious bronchitis virus in my memory, which isn't all that trustworthy these days.