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This is a prospective study of 431 patients (862 knees) with patellofemoral pain, patellar dislocation, or other abnormalities of the knee joint. There were 217 asymptomatic knees with no contralateral problems for comparison. All patients had a history and physical and radiographic examination of both knees. The radiographs included standard anteroposterior views, axial views at 30 degrees of knee flexion, and standing lateral views at 0 degree and 30 degrees of flexion. The presence of patellar tilt or subluxation was noted on the axial view. The lateral view of the patella, with precise overlap of the posterior femoral condyles, allowed determination of relationships between the patella's medial edge, median ridge, and lateral edge to assess patellar tilt. Sixty-two percent of patients with patellar dislocations demonstrated subluxation on the axial view, while 98% demonstrated an abnormal lateral view. Eighteen percent of the control knees revealed evidence of subluxation on the axial view while 35% demonstrated subluxation on the extended lateral view. The axial view demonstrated 62% sensitivity for dislocation, while the lateral view taken in full extension demonstrated 98% sensitivity. The specificity for previous dislocation was 82% for the axial view and 93% for the lateral flexed view. Given the high sensitivity of the lateral view for detecting prior patellar dislocation, a normal result on this view can virtually eliminate the question of previous dislocation. Also, with the high specificity of the axial view and lateral view with knee flexion, the two views combined can confirm a clinical impression of patellofemoral malalignment.

Summary. Three in number, the plicae are inconstant synovial structures found within the cavity of the knee joint, and have been recognised for some time. The inferior plica in particular was described by Vesalius in 1555. Both the inferior and medial plicae are vestiges of an intermediate articular disc similar to the menisci. The superior plica derives from the wall which in the first instance, separates the bursa and quadriceps cul-de-sac.One knee joint out of four retains the medial plica. We have divided it into two types according to its size. 6% of knee joints have a large plica (type II) which according to our observations is the type most likely to become clinically symptomatic. Rather more than one knee out of two has a superior plica: we have identified three types according to the completeness of the split in the wall dividing bursa from quadriceps cul-de-sac. Two knee joints out of three have an inferior plica; here again we have identified three types according to the degreee of extension of the plica antero-posteriorly. We thought it of practical usefulness to describe the radiographic anatomy of each plica.It seemed particularly worthwhile to restructure the anatomical findings, based on 200 dissections, in the more general context of clinical anatomy. Les plicae. Etude anatomique portant sur la dissection de 200 genouxR6sum& Au nombre de trois, les plicae sont des formations synoviales inconstantes de la cavit6 articulaire du genou qui sont connues depuis longtemps. C'est notamment le cas de la plica inf6rieure d6crite par V6salius en 1555. Plica inf6rieure et plica m6diale sont toutes deux des vestiges du disque interm6diaire ~t l'exemple des mbnisques. La plica Sup6rieure d6rive de la cloison qui s6pare initialement bourse et cul-desac sous-quadricipitaux.Un genou sur quatre pr6sente la plica m6diale. Nous en avons isol6 deux types en fonction de sa largeur. 6% des genoux pr6sentent une plica large de type lI qui d'apr6s nos constatations seraient celles qui pourraient devenir symptomatiques. Un peu plus d'un genou sur deux pr6sentent la plica sup6rieure. Nous en avons isol6 trois types calqu6s sur la d6his-cence plus ou moins compl6te de la cloison initiale. Deux genoux sur trois pr6sentent la plica inf6rieure. Nous en avons aussi isol6 trois types suivant l'btendue ant6ro-post6rieure de la plica. Pour chaque plica, nous avons jug6 utile de dbcrire son anatomie radiographique.I1 parait utile de reclasser cette 6tude anatomique, portant sur 200 dissections, dans le cadre plus vaste anatomo-clinique.

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