Crepitus (in the knees) is a fine crunching noise, usually on bending the knee from standing, reminiscent of crushing a packet of crispie rice breakfast cereal.
In the early stages it is felt, rather than heard, by laying the palm of the hand on the kneecap and bending the knees (while standing).
There is no clear consensus as to the mechanism of production of the sound, although most are in agreement that the kneecap mechanism is involved.
Surgeons tend to be concerned about crepitus only if it is accompanied by pain, and talk of 'physiological crepitus'. But there seems to be a continuum, where the timbre of the crepitus can be measured and shown to alter progressively as symptoms progress.
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