Peter Mcnair PHD and Lecturer at AUT in Auckland NZ has developed a great assessment tool for lower limb function in two parts first Activities of Daily Living and second recrational activity scaling baseline tasks, its application before and after surgery and over time provided scores out of 40... the progression is clear and may be what you are looking for . I recommend you seek his permission to look at it and use it to develop your own.I am sorry I don't know his email address but you should be able to find him via google. Good luck