Should I take time off in my exercise?

I am 71 years old. I was ill and bedridden for almost 2 years with several illnesses. I got almost no exercise during that time. I started getting better slowly about 4 months ago. I am seriously overweight (need to lose over 50 lbs). I have arthritis. I had an accident 3 months ago and injured my right knee (strained muscle) . The nurse at my doctor's office told me I would never walk again without the use of a walker. I refused the walker and went online to the Mayo clinic and exercised my knee slowly for a few weeks, then walked in a cane and began swimming daily. Now I walk without a cane though it hurts after about 5 minutes. I am up to swimming steadily for about 45 min.to an hour a day.
My legs are getting stronger and more muscular but some mornings it takes ibuprofen to get me out of bed in the morning. Would I be better off swimming every other day? Do my leg muscles and shoulder muscles need time to heal between swim sessions? I have lost 18 lbs in 3 months dieting and swimming.