Chondromalacia, osteoarthritis, malalignment, subluxation, patellar instability, and anterior knee pain are all terms relating to specific knee disorders which can be generally characterized as instability of the patellofemoral joint. Among the tools employed to diagnose patellofemoral joint dysfunction, is radiological assessment. However, as pointed out in Teigte, R. A., "Radiology of the Patellofemoral Joint", CPEC, 1985, radiographic evaluation in many cases is unsatisfactory because x-rays of critical views of the joint are omitted or improperly taken. Nonorthopedic personnel often do not have the expertise to perform such x-rays, in which case emergency diagnosis of patellofemoral joint instability may be inadequate. The result can be prolonged recovery or, in the worst case, incomplete recovery.
Given the inherent complexities and risks of radiological assessment, additional diagnostic tools are needed to augment or supplant radiological means in the diagnosis of patellofemoral joint instabilities. Although devices exist for physically evaluating the integrity of the knee, such devices have not proven sufficiently specific for diagnosis of patellofemoral joint instability. As such, physical means are needed for directly acquiring meaningful and reliable diagnostic data specific to the patellofemoral joint. Further, physical means are needed for acquiring diagnostic data specific to the patellofemoral joint in a relatively economical and practical manner. Further, physical means are needed for acquiring diagnostic data specific to the patellofemoral joint which enable accurate and thorough treatment of patellofemoral joint instabilities.