Stress radiographs of the patellofemoral joint.
Patellar instability is usually diagnosed on the basis of the clinical presentation without radiographic confirmation. In the present report, we describe a new radiographic method to demonstrate patellar instability. Axial radiographs were made of the patellofemoral joint of ninety individuals (180 knees) and were then repeated while a medial or lateral force was applied to the patella. The applied force was kept constant with use of a specially designed instrument. The ninety individuals were divided into four groups on the basis of the clinical findings: normal, lateral instability, medial instability, and multidirectional instability. Stress radiographs differentiated the four groups and confirmed the clinical diagnosis in all patients who had unilateral symptoms. A four-millimeter increase in medial or lateral excursion of the patella excursion of the asymptomatic knee was significant (p < 0.0001). Stress radiographs offer a simple method for the measurement of force-displacement relationships in the patellofemoral joint and for the demonstration of patellofemoral instability.
Teitge
R A
RA
Department of Orthopaedic Surgery, Wayne State University School of Medicine, Detroit, Michigan 48201, USA.
Faerber
W W
WW
Des Madryl
P
P
Matelic
T M
TM
D000328:Adult; D006801:Humans; D007593:Joint Instability / Q000000981:diagnostic imaging*; D007719:Knee Joint / Q000000981:diagnostic imaging* / Q000503:physiopathology; D011859:Radiography / Q000379:methods; D013314:Stress, Mechanical