What is the knee thing when making out?

Some people experience a sensation in their knees when they are making out, which may be due to a variety of factors such as excitement, arousal, or increased blood flow to the area. This sensation is often described as tingling, weakness, or trembling in the knees, and can be a normal response to the intense physical and emotional stimulation of kissing and being close to a partner. Additionally, the act of standing or being in a certain position for an extended period of time can also contribute to the sensation in the knees. If the sensation is uncomfortable or persistent, it's important to communicate with your partner and adjust your position to ensure both partners are comfortable and enjoying the experience.