A fall of the knee, if it is only a superficial skin abrasion or soft tissue contusion, will usually manifest as a skin breakdown in the anterior patellar region of the knee, and if the abrasion is deep, there will be blood and fluid leakage, and local soft tissue contusion will lead to local swelling and pain. If the suprapatellar capsule or joint capsule is accidentally bruised, there may be extreme swelling of the entire joint and even joint effusion, and the floating patella test is positive. If the patella is accidentally dropped to the point of fracture and the patella is not displaced, but only cracked fracture, pain will occur when pressing on the patella, and the pain will increase when the knee is bent. If the patella is displaced after the fracture, you can touch the patella where there is a sensation of bone rubbing, the displacement is serious it is possible that the massage is more empty at the original patella position, you can feel the two fracture ends of the patella are displaced upward and downward.