<s>[INST] I was running today, training for a half marathon and I tripped and fell with all the brunt of it on my left knee. I did have a brace on since I have severe osteoarthritis in it. Now it is extremely swollen and I cannot bend it without terrible pain. What should I do! [/INST] Hello, It could be a contusion or sprain. Consult an orthopaedician and plan for an MRI scan for further assessment. As of now, you can apply ice packs for faster recovery. Hope I have answered your query. Let me know if I can assist you further. Take care Regards, Dr Shinas Hussain, General & Family Physician </s>