Baby do caress knee ringing, may be related to physiological factors, may also be due to patellofemoral arthritis and other reasons. 1. physiological factors: common in younger babies, due to the ligaments around the knee joint, the joint capsule is not fully developed, resulting in the knee joint is relatively loose, it is easy to cause the knee joint ringing, especially to do caressing, often appear obvious knee joint ringing. 2. Patellofemoral arthritis: usually caused by improper posture or patellar developmental disorders when the baby movement, due to the presence of patellar inflammatory reaction, under the stimulating effect of inflammation, can lead to knee ringing, especially when doing caressing, the symptoms are more pronounced, but also may be accompanied by knee pain, swelling and other symptoms. Baby do touch knee ringing, may also be caused by other reasons, if accompanied by obvious symptoms of discomfort, should seek medical attention as soon as possible, after diagnosis of the cause, give targeted treatment.