5 months still early on ….. I know probably sick of hearing because you are living it but takes time…..stairs are the hardest to conquer, so I am not surprised they are difficult…I gather your flexion numbers are low ….towel slides will help , hangin knee off edge of bed. just keep up with your therapy it does get better ….they are right won’t show anything , even after a year dr are reluctant to do mri or scan , I had tkr manipulation, year later new dr revision … three years later right back where I started pain stiffiness … I am one of those people that develops to much scar tissue… so there is nothing Dr can do for me .., best thing he could have told me was no surgery or procedure that will make this better … now I focus on pain management with laser and PEMF mat …. Good luck in your journey but right now just do the foot work and have faith it will get better