Continuous passive motion in computer assisted auscultation of the knee.

A study of physiological patellofemoral crepitus (PPC) signal recorded from adolescent knees has yielded information which suggests that decay time of PPC amplitude due to continuous passive motion (CPM) activity is a consistent and useful signature variable for a given knee. The PPC vibrational signal was induced in each case by 1 min of static load on the patella and postural variables during the examination were carefully controlled. The speed of CPM has been noted as a factor directly influencing the rat of PPC amplitude decay; specifically, a higher CPM speed contributes to an increased decay constant at a cost of increased inter-subject variability. It is proposed that CPM might form an important basis for the ultimate development of a computer-based auscultation technique for diagnosis of patellofemoral joint disorders.