The feeling of something jumping in the knee may be due to the following reasons: 1. There may be infection inside the knee joint, such as infection inside the knee joint secondary to trauma, or infection inside the knee joint secondary to systemic infection, then there may be throbbing pain inside the knee joint, accompanied by redness, swelling and heat on the surface of the knee joint. 2. 2. It may be caused by muscle spasm in the thigh, such as cold or excessive fatigue in the thigh, resulting in muscle spasm, or cramping, which may lead to twitching sensation around the patella. 3. It is caused by peripheral neuropathy, such as the onset of lumbar disc herniation, which may produce radiating pain and lead to throbbing pain. 4. For example, when the arteries of the lower limbs are occluded or narrowed, it is possible to feel throbbing pain or a throbbing foreign body sensation.