Mary, age 58, complains that every time she walks up the stairs, her joints "pop" and "click." what is mary describing?

The answer is crepitus. This is a therapeutic term to depict the popping, grinding, crackling sounds and sensations experienced in the skin and joints because of the nearness of air in the subcutaneous tissue.

Different kinds of crepitus that can be heard in joint pathologies are:

Bone crepitus

Joint crepitus

Crepitus of bursitis

Crepitus of tenosynovitis