Imaging Quiz Answer: Closed Reduction of an Everted Patella

Richard B. Ganong, MD

The Author's Solution

Return to case presentation

The problem was how to invert the patella so it could be reduced. Intra-articular lidocaine hydrochloride was administered, but an attempt to move the patella with the leg still extended was unsuccessful. The knee was then gently and easily brought into 90° flexion over the table edge. Next, the tibia was brought into gentle external rotation as the patella was forcefully rotated 90° by pushing the posterior aspect medially and the anterior aspect laterally (figure 2). This presented the treating physicians with the anatomic alignment usually seen with lateral patellar dislocations-facets facing medially. The patella was then easily relocated into the trochlear groove with extension of the knee and pressure directed over the lateral edge of the patella. Further examination revealed no ligament or neurovascular damage.

The patient sought follow-up with her hometown physician, who placed her in extension in a cylinder cast for 2 weeks. She later underwent physical therapy and has returned to full activity.

Discussion

To my knowledge, a closed reduction of an everted laterally dislocated patella has not been reported in the medical literature. A comprehensive literature search revealed one such case (1), which required open reduction. In addition, I contacted seven orthopedic colleagues who do extensive knee treatment, and only one had seen an everted, laterally dislocated patella. His patient required open reduction.

With the knee in 90° of flexion, external rotation of the tibia appeared to be key in relaxing the quadriceps-patellar tendon to allow rotation of the everted patella to a more normal position. It was also important to ascertain which direction the patella should be rotated to achieve a reduction. The radiograph demonstrated that the facets were facing laterally. The shortest rotational distance to this dislocated position is 90°, not 270°. Thus, to relocate, the reverse rotational distance was deemed appropriate.

Thus, reducing an everted patella involved several key elements:

(1) visualizing the proper rotational distances,
(2) relaxing the quadriceps-patellar tendon by flexing the knee 90° and externally rotating the tibia, and
(3) avoiding excessive force.

Reference

1. Corso SJ, Thal R, Forman D: Locked patellar dislocation with vertical axis rotation: a case report. Clin Orthop 1992;Jun(279):190-193

Dr Ganong is an internist with the Truckee Tahoe Medical Group in Tahoe City, California. He is a fellow of the American College of Physicians. Address correspondence to Richard B. Ganong, MD, Box 2649, Olympic Valley, CA 96146.

RETURN TO FEBRUARY 1996 TABLE OF CONTENTS