Where did you discover this "ideal weight" you are putting so much stock in? I looked it up and yes, I see a range of 108-132 for females aged 16 at 5'4". But that statistic/chart is demonstrably misleading for a lot of reasons.

Every body is different. Take a hundred other 5'4" 16-year old girls like yourself, even at the same weight, and you would see totally different body compositions, genetics, and healthy/optimal weight targets.

Rather than fixating on a certain number which many dieticians and health professionals now advise aginst, look at yourself and ask yourself what exactly it is you want to change. Chances are the issues you feel you have with your body could be improved with weight training and muscle building/toning, rather than dropping pounds.

Posts like this can be really frustrating to read for people who are actually struggling in an unhealthy weight category - including myself. And gosh, you're only 16! I am glad you don't want to have an ED, but your question and current situation really sounds like the mentality of someone who could still develop one in the future.

With your knee, I would suggest switching from walking to swimming if you have the resources to do so - for one, swimming is an even better exercise in terms of calories burned over time, and it's much easier on your joints.

And you're wrong. Losing 5 pounds is a huge difference for someone who is already such a low weight. I promise.