Usually clinically we do patellar grinding test to assess for patellofemoral degeneration. persistant pain while squatting,kneeling and getting up from sitting position are more linked with patellofemoral altered kinetics. Patellar crepitus must be differentiated from patellar snaps or clunk as it indicates joint degeneration moderate to severe.

Dear Shahnaz. 

How very interesting.

I often search for articular crepitus, as a sign of arthritis., on my practice. I wouldn't think of measuring it's intensity, but it might be interesting to seek for this relation in terms of graduating degrees of arthritis...

(Nevertheless, I think not. This is a physical sign to pursue diagnosis. And as you know, arthritic symptoms have great fluctuations and variations in regards to the time of day, the weather humidity, ageing, and so on... The signs would also vary individually and with the accompanying symptoms variations)

An interesting question. Years back I started my career with this question.  We tried to record the sound from the joint using a microphone attached to the knee - an experiment not entirely successful. 

Crepitus apparently has no direct relationship to knee OA. It frequently decreases when a knee becomes inflamed or has fluid in the joint, a common occupancy as knee OA becomes more severe. 

Best best in can be an early sign of OA if it is present. 

Siddharth Das