Knee injuries are a common concern in orthopedic and sports medicine, often requiring extensive rehabilitation to restore function and alleviate pain. The rehabilitation process can be long and challenging, necessitating innovative approaches to engage and motivate patients effectively. Serious games have emerged as a promising tool in rehabilitation, offering an interactive and enjoyable way to perform therapeutic exercises. In this context, a new serious game that leverages the Wii Fit Balance Board as an input device supported by a keyboard to aid knee rehabilitation was developed. To tailor the game to the specific needs of knee rehabilitation, qualitative content analysis and requirement extraction based on three interviews with therapists were conducted. These insights were then iteratively integrated into the game’s development, ensuring that the final game was both clinically relevant and engaging. A therapist subsequently re-evaluated the completed game, confirming its potential to enhance the rehabilitation process. It was also shown that further research is needed to detect squat movements on the Balance Board. But this initial approach, combining the Wii Fit Balance Board with squat exercises, uniquely addresses the challenges of knee rehabilitation, offering a novel video and game solution.