On an upright bike pain above the knee "usually" means the seat is too high, and pain below the knee that the seat is too low.

On an upright bike, as you press down on the pedals weight is lifted upward, and the hardest you can press is limited by your weight (and to a degree by pulling up on the handlebar.) On a recumbent bike your legs are pressing against the pedals and cannot push your back any further than the seat back. In other words there is no natural safety release for pressing too hard. If you have really strong legs you are unlikely to hurt yourself on an upright bike, but you can easily damage your knees on a recumbent if the muscles are stronger than the tendons and ligaments. Additionally, you are using different muscles in different ways on a recumbent. There are several ways to hurt yourself on a recumbent if you just jump on and expect to ride it like an upright bike.

My wife and I have proved this to our satisfaction over a period of many years. She rides a TRICE now and we just sold a Rans Rocket and a Lightning R-84. As I type this my patellar tendon is crying for attention. Our last Labrador Retriever had to have an anterior (caudal) cruciate ligament tear corrected surgically. She never rode, but she spent a lot of time in a recumbent position.