Prosthetics. You need to see a licensed prothetist and orthotist in an orthopaedic brace shop to be properly evaluated and fit with prosthetics due to your limb loss. Lots of hybrid joint combinations available based on the level of amputation. Would also strongly recc aggressive physical therapy after fitting to retrain you to stand and walk! Best of luck and god bless!
They are custom. Lower extremity prosthetics are modular and custom. The best prosthetic will be the one that allows you to perform the activities you are interested in without pain or discomfort. In these terms the "best" will vary from person to person. A good rehab team will help you determine what is the best system for your particular needs.