OBJECTIVE. The purpose of this study was to determine if kinematic CT
can be applied to the patellofemoral joint using current slip-ring CT
scanner design in patients with anterior knee pain and thus a suspecte
d patellar tracking disorder. SUBJECTS AND METHODS. Twenty knees in 18
patients with anterior knee pain were evaluated with kinematic CT. A
single 10-sec exposure of the patellofemoral joint was obtained during
active flexion and extension. Static nonkinematic and loaded kinemati
c examinations were compared with unloaded kinematic studies in a subs
et of patients. The changes in lateral patellofemoral angle and latera
l shift were measured. Video cine viewing of patellofemoral motion was
used to subjectively grade image quality and patellofemoral abnormali
ties by consensus. RESULTS. Kinematic CT was successfully used in ail
20 knees. In nine knees studied with static nonkinematic and unloaded
kinematic images, the lateral patellofemoral angle improved an average
of 4 degrees on the kinematic images. In addition, lateral shift impr
oved by an average of 3%, an improvement that was statistically signif
icant (p = .01). In 10 knees studied with and without loading, the lat
eral patellofemoral angle decreased an average of 3% with loading. No
significant change was seen in lateral shift. In all patients, cine vi
ewing wets thought to be more useful than single images. Cine viewing
was of good or diagnostic quality in all 20 knees studied. Lateral pat
ellar translation during extension was detected in eight of 20 kinemat
ic studies. Lateral patellar tilting also was detected in eight of 20
kinematic studies. Narrowing of the articular space was detected in 12
of 20 knees. Six knees were determined to be normal. CONCLUSION, Kine
matic CT with slip-ring technology is a new technique that can be easi
ly performed on the patellofemoral joint. This technique shows promise
as a tool for determining the cause of anterior knee pain.