I have a swollen, very painful knee. I have had
Acute exacerbation of osteoarthritis...
This seems to be acute exacerbation of osteoarthiritis. The clicks and sounds arising from knee are part of osteoarthritis symptoms, If the knee cortisone injections helped last time, we should try this again. But I understand the doctor is away.
Until then there are some measures like icing the area, resting / immobilization and over the counter pain medications available to treat the problem. However based on the severity, I am not sure how far these home measures will be helpful. Therefore in my opinion, the best approach will be to visit ER and explain the situation. ER doctors should be able to prescribe pain medications most like opioid drugs until the doctor is back for cortisone shots.
Hope this helps. Let me know if you need clarifications.