limited range of motion after tumor removal?

Hi All.  I was dx'd with a MFH soft tissue sarcoma earlier this year and it was removed in May after many rounds of chemo and radiation.   As my tumor grew on the back of my leg, my leg became severely bent and I became unable to use the leg and walk.    Now that the tumor has been removed, even 2 months later, my ability to extend my leg has not improved and it's still bent at a nearly 90 degree angle.

Prior to my diagnosis, I was extremely active - running daily, going to yoga, running after my toddler son.   Losing this ability to extend my leg - and walk - has been devastating.  I was hoping that removing the tumor would be the end of this journey, but it hasn't. 

Physical therapy has been useless in rehabilitating the leg.   My ortho oncologist has suggested a few different means of solving this problem - botox to help paralyze some muscles so i can work on lengthening/stretching other muscles, a surgery to cut the hamstring muscles, a total knee replacement. 

Has anyone had any experience with any of these procedures and have any of them been successful?  Of course, I'd like to walk again without significant impairment and the use of any aids like walkers or canes since I'm still pretty young.