J Korean Radiol Soc.  2001 Oct;45(4):411-415. 10.3348/jkrs.2001.45.4.411.

MR Findings of Traumatic Transient Lateral Dislocation of the Patellae

• Lee JH
• Seol HY
• Kim SM
• Ahn JM
• Shin MJ

• KMID: 1832937
• DOI: http://doi.org/10.3348/jkrs.2001.45.4.411

Abstract

PURPOSE
To determine the magnetic resonance (MR) imaging characteristics of traumatic transient lateral dislocation of the patellae.
MATERIALS AND METHODS
In eight patients (6 males, 2 females, mean age: 22.4 years) in whom transient lateral dislocation of the patella was diagnosed, the distinctive MR imaging findings reflecting known injury mechanism were retrospectively analyzed with regard to bone contusion, chondral defect, fracture, loose body, joint effusion, and the associated soft tissue abnormalities.
RESULTS
All of eight patients had bone contusions in the lateral femoral condyle and medial facet of the patella, while in five, chondral defects were present in this latter region. In three patients, fractures of the on lateral femoral condyle (n=2) and medial facet of the patella (n=3) were noted, and in three others, loose bodies were noted. Joint effusion [simple effusion (n=4), lipohemarthrosis (n=3)] was observed in seven patients, and associated soft tissue injuries [to the medial patellar retinaculum (n=8), patellar tendon (n=2), and anterior cruciate ligament (n=1)] in eight. Patellar subluxation was found in seven.
CONCLUSION
MR imaging is a useful technique for the diagnosis of traumatic lateral dislocation of the patella. The significant MR findings are bone contusion in the lateral femoral condyle and medial facet of the patella, chondral defect, fracture, joint effusion, injury to the medial patellar retinaculum, and patellar subluxation.

Keyword

Knee, injuries; Knee, MR; Patella

MeSH Terms

Anterior Cruciate Ligament
Contusions
Diagnosis
Dislocations*
Female
Humans
Joint Loose Bodies
Joints
Magnetic Resonance Imaging
Male
Patella*
Patellar Ligament
Retrospective Studies
Soft Tissue Injuries