Hello,
Have any of the investigations, assessments revealed anything in particular?
Is the knee joint space diminished, are there bony spurs, have tests been completed to confirm this?
Often conditions such as chondromalacia are either due to or intensified by muscular imbalances of the quadricep muscles, as these attach to the knee cap (patella).
I reckon since this is an ongoing problem, there may be significant muscular adaptations around the knee joint. The stresses that are being imposed on the knee joint may be due to the incorrect muscles activating during movements. It appears that gait re-training helped in this respect.
I would be weary about going under the knife considering you have not really achieved recovery with physiotherapy. Unless it is indicated I would get a re-referral to a Physio who is willing to help you workout the strength imbalances that are affecting the knee in particular.
Regards