Thank you for your interest in King Brand. Absolutely, the BFST can help injuries as old as 5 or 20 years. BFST is promoting blood flow and optimal circulation to the affected area. As long as you are also keeping inflammation down, keeping good, nutrient blood flow through the knee will help heal any damaged tissues. One 20 minute treatment will promote the circulation for a good 3-4 hours after. Recommended treatment in the beginning would be 3-5 times a day.
Because it is an older injury, it may not fix it completely but will give you a lot more relief on those cold days compared to now.
I hope this information helps and wish you all the best.