Welcome to the forum.
Your current BMI is 36.6 and you will have a BMI of 25 when you weigh 200 pounds...
That is a good goal.
You do not have to do things like running and jumping for it to be effective exercise.
Walking for instance is a very effective form of exercise if your knees are up to it.
Swimming is also excellent for people with joint problems because you are supported by the water.
Obviously weight training can be done to focus on all sorts of muscle groups so you can do plenty of exercise without putting a strain on your knees.
There are two sides to the calorie equation however and control over your food could enable you to lose weight even if for any combination of reasons you were unable to exercise at all.
You definitely should work on making your food plan more healthy and ensure that you eat calories at an appropriate level for weight loss... There are accurate ways of measuring your calorie needs but these calculations can get quite complex.
The simple rule of thumb almost always results
whereby most fairly active people will maintain their weight on a calorie level of 15 * their weight in pounds
and most fairly active people will lose weight on a calorie level of between 8 * and 12 * their weight in pounds...
Therefore (since you might have a reduction in exercise range due to your injury) it is simplest to simply shoot for a calorie level of about 10 * weight in pounds every day and see if you lose weight... if you do - keep on doing that (recalculating) - certain in the knowledge that it naturally reduces as your weight reduces...
If it doesnt work - I would suggest that you check your weighing of portion sizes (scoops and other approximations can be prone to a lot of error) and if you still get no results you can drop to nearer the 8 * weight calorie level...
I would tend to see how 2830 calories went for you to start with...
I also suggest that you read this thread - as it might help you to settle in here...
http://weight-loss.fitness.com/threads/57955-My-advice-to-newcomers
Good luck