My Husband Is Suffering From Severe Knee Pain. It Is

My husband is suffering from severe knee pain. It is swollen, he is very active, hunting and umpiring 100s of baseball games a year. He doesn't recall doing anything to cause the pain he just woke up to the pain on Wednesday. It seems to be getting worse and the swelling is getting worse. He recently lost insurance and we are concerned about the best choice for next steps.