Hi, welcome to our site. I am Dr Saumya Mittal. Read your query. That is a very significant question and i appreciate your problem. I will try my best to answer your query The pain, coldness and numbness may be secondary to the trauma you have had. You have not mentioned how long back this accident happen so I can only guess that its recent and so is causing you trouble. Of course if you have a prior arthritis, the joint is already affected and any trauma may cause problem to you much much more than someone who is unaffected arthritis. As for knee replacement, there is no lower age limit for knee replacement, unless we are expecting a growth of bones,and therefore joints. Get an X ray of the affected for sure, This will help confirm that you dont have any serious problem I hope this helps you. Inform the reports mentioned above so i can be of help further. Best of luck. I have given you the answer to the maximum considering the information provided. The results of the tests could further enhance my answer to you. Please do understand that some details could be extracted from a detailed history and examination. Looking forward to your return query with the details asked so that I can help you further. (If the answer has helped you, please indicate this)