Keeping knees bent for long periods leads to increased pressure in the patellofemoral joint, which is the joint behind the knee cap. This might lead to pain.
Next Steps
Take a 5 minute break every hour to stand up, straighten your knees and perform mild stretching exercises.
Do not sit in one place for long.
Sit in a proper posture with back support, elbow support.
Keep the laptop at the level of your eyes. Do not bend your lower back or neck for long periods.
Video consult with me if your problem continues even after the following this advice.