Joint ill is a bacterial infection that foals are suspetible to. We think Harley got it as his dam is in a raging heat and urinates all over herself. I was trying to wash her down but its impossible to keep her clean when shes in such a strong heat. Then we he goes to nurse he probably picked up bacteria. It settled in his knee joint. Hopefully the antibiotics will get rid of it. I called my vet today and hes out of town till monday.