Last course I attended said the current wisdom was not to do meniscal knee lesions over 50 in part because there are too many degenerate tears by that age. With the weight issue, I would have thought that even more likely.
Instability could be helped by Knee Dextrose Prolotherapy. (multiple studies showing benefit).
Pain can be helped by
Cooled Knee Geniculate Nerve Radiofrequency Ablation
Cooled Radiofrequency Ablation of Genicular Nerves for Knee Osteoarthritis Pain: A Protocol for Patient Selection and Case Series. - PubMed - NCBI
Cooled Radiofrequency Ablation Relieves Osteoarthritis-Related Knee Pain - Clinical Pain Advisor
One version is called COOLIEF* Cooled Radiofrequency System. Probably not cheap...
I have not had much luck with stem cells