My boyfriend has bad knees - the cartilage in them is broken up and feels like sand inside the joint. Therefore, they are extremely painful. He can barely walk for 5 minutes with out them hurting immensely, let alone doing any other kind of exercise. Even getting of the sofa or walking up the stairs causes him a great deal of pain in his knees.

Because of this he's doing the least amount of physical activity he's ever done, and as a result of that, he's constantly tired, lethargic etc. He's also put on a bit of weight.

I would like to help him find a way to get his body moving more without putting unnessary strain on his knees. Swimming is not an option as he hates water. So, I thought lifting weights may help as although he's not moving his whole body, he is expanding some energy by doing this (even if he is sitting whilst lifting them), and it might help the lethargy.

I am no expert and wondered if this logic is correct - will lifting weights help his lethargy? Are there any other experts you can suggest which dont invlove strain on the knees? (as I mentioned, even walking for 5 minutes can cause pain)

Many thanks