If it was only meniscus surgery it would be NP. Lin had the same surgery and was criticized for not coming back in the playoffs 8 weeks after his surgery. I think JR had a combo surgery, a scope to repair the torn meniscus and patella tendon knee surgery.
Not a doctor but guys come back from knee surgeries. Just glad it wasn't the dreaded microfracture surgery or Brandon Roy's knee problem where he had no cartilage left in his knees.
I would bet they insured his contract otherwise why risk signing him if an insurance company wouldn't risk insuring him.