How do I increase HDL level if I am unable to walk due to weak knee?

Many strategies. Exercise does raise HDL but is also important for cardiovascular fitness and weight control. Get treatment (? PT) for your knee; swimming is an exercise that you can do with a weak knee. A diet low in sugar/simple carbs, Vit. D, eating fish and/or fish oil, a glass of red wine, eating other foods that are red/purple, dark chocolate, green tea, almonds & walnuts and avoiding hydrogenated oils help.