What Causes Cracking Sound From Knee, Ankle And Shoulder?

Hi I m a 14 year old boy an every time I kneel over my knee makes a craking noise as though the bones are hitting against each other and recently the bottom half of my leg has also started hurting some times other bones also make the same noise such as my ankle shouldrer and wrist I also lift weights an the only exersie I can t do is squats becausr my knee all of a sudden loses its strength an feels weak