Common symptoms of knee pain include swelling, stiffness, redness, warmth, weakness, instability, and limited range of motion. The severity of symptoms can vary depending on the underlying cause. Some people may experience mild discomfort, while others may have severe pain that limits their mobility. Additional symptoms may include clicking or grinding noises when moving the knee, locking or buckling of the joint, and difficulty bearing weight. Paying attention to the specific symptoms can help identify the cause and guide appropriate treatment.