Sudden pain in the knee joint is mainly considered acute diseases or acute attacks of chronic diseases, which can lead to sudden pain in the knee joint. There are several common causes: 1. Acute trauma, including sprains, contusions, bruises, and blows, can cause sudden knee pain due to acute injury, and fractures can occur in severe cases, causing severe pain and functional impairment. 2. 3. Sudden onset of pain and dysfunction due to bone diseases of the knee, such as tumors or metabolic diseases of the bone that result in a decrease in bone strength and sudden pathological fractures. 4. Chronic metabolic diseases, such as gout. The symptoms of gout may not be obvious, but when the blood uric acid suddenly rises and is deposited around the knee joint, gouty knee osteoarthritis may occur, and the knee joint may suddenly become painful and accompanied by redness, swelling, heat and pain.