Many people have some degree of crepitus, a crackling or grinding sound made when uneven cartilage surfaces rub against each other.It usually occurs in large joints, like the knee or shoulder.

• 很多人都有不同程度的捻发音，凹凸不平的软骨组织表面互相摩擦的时候会发出的一种噼啪声或者研磨声，通常发生在膝盖或者肩膀这样的大关节。