Rehabilitation of Hyperextended Knee

Hi All

I have been referred to treat a 61y.o. female for rehabilitation of posterior knee pain caused by knee hyperxtension when she walks. Here is some past history:
Suffered from polio in left lower limb as a child, has had poor dorsi flexion and ankle control since, as well as general weakness in that limb
5 years ago she had a #hip and femur and has a rod through her R femur
1 year ago she had a fall and # pelvis, she stayed in hospital and commenced in patient rehab while wearing a zimmer knee brace
The patient claims she was never able to walk the same with the brace, so she went to another rehab centre who provided her with a brace yet she feels unstable and unconfident with it on, seen an ortho who advised her to remove it.

Current history
Patient living at home by herself, uses a walker to mobilise and has home help care 1 - 2 hours/ day, but is otherwise independent
Is unable to actively extend knee in any range, even as small as 5 degree flexion
She does not want to wear a brace for support

My Treatment so far
Gait re-training with my hand behind knee as feedback (did not seem to help)
Knee taping for feed back (no help - weak quads meant knee woudl always hyperextend)
Knee taping into 1-2degree flexion ( the patient felt unsteady and was OK when i was around treating her but felt unsafe when mobilising on her own so is took it off due to risk of falls)
Trialled Acupuntcure around knee and L/sp with ISM quads exercises post
I have even tried Muscle Stim aroudn quads but to no avail

In my opinion I believe she is best to visit an outpaitent rehab centre to improve her gait. However due to her poor experiences in the past she is not so fond of this.

Does anyone have any other option or opinion ?? It would be much appreciated

Thanks
Johnny
ISM knee ext 200 reps per day