The sensation that your knee needs to pop is commonly caused by one or more of the following reasons:

• Release of gas bubbles (cavitation) from the synovial fluid in the knee joint, which is harmless and similar to knuckle cracking. The popping happens when the joint pressure changes and gas bubbles collapse.
• Joint irregularities such as changes in the movement of the patella (kneecap) causing friction or altered tracking.
• Inflammation or irritation in the knee joint.
• Early signs of osteoarthritis, where cartilage wears down and causes increased friction between bones.
• Meniscus or ligament injuries, which can cause instability and popping sounds, sometimes with pain.
• Patellofemoral pain syndrome or runner’s knee, where the kneecap does not move smoothly in its groove.
• Tendons or ligaments snapping over bony structures in the knee during movement.

If the popping is not accompanied by pain, swelling, or instability, it is usually harmless. However, if there is pain, swelling, limited motion, or a feeling the knee is unstable, medical evaluation is advised as these may indicate injury or arthritis needing treatment.