title: Stress radiographs of the patellofemoral joint.
abstract: 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.
authors.affiliation: Department of Orthopaedic Surgery, Wayne State University School of Medicine, Detroit, Michigan 48201, USA.
authors.forename: R A
authors.initials: RA
authors.lastname: Teitge
authors.forename: W W
authors.initials: WW
authors.lastname: Faerber
authors.forename: P
authors.initials: P
authors.lastname: Des Madryl
authors.forename: T M
authors.initials: TM
authors.lastname: Matelic
mesh_terms: 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