<s>[INST] I have been down with influenza past week and have experienced instability in my left leg function. This has resulted in me falling several times. It seems as though the leg collapses without warning . I am generally in great health, quite active, and no know chronic diseases. [/INST] Hello, Welcome to the magical world of health care, I went through your query, and such instabilities with history or repeated falls indicate towards internal derangement in the knee ligaments mainly ACL and PCL, what you will need is an MRI of the knee joint followed by probably arthroscopic reconstruction of the ligaments if they are torn. I hope my advice would have been useful, in decision-making regarding your treatment, still if you have any clarifications or doubts feel free to contact back. Thanks. </s>