Welcome to EmpowHER and thank you for coming to us with your question.
As much as I would like to offer suggestions, you must consult your physician. I am concerned about your limited ability to bend your knees. Your physician is aware of all your medical conditions, your actual height and weight, and level of mobility.
Please consider discussing this with your health care provider. I would not want to recommend anything that could harm you.
In general, the best way to lose weight is to burn more calories than you consume. If you have an inactive lifestyle, exercise should be introduced slowly and gradually. In cases of extreme obesity, weight loss surgery is an option. Every one is not a candidate.
Please feel free to return with any further weight loss or exercise questions once you have spoken with your doctor.