X-ray of patellar dislocation and subluxation
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Author:
Mikael Häggström [notes 1]
Contents
Planning
Images must include an axial (skyline) view.
Evaluation
In obvious patellar dislocation, make a rough estimation of the distance compared to normal position.
In borderline cases of subluxation, preferably apply the following measurements:
- The lateral patellofemoral angle, formed by:[1]
- A line connecting the most anterior points of the medial and lateral facets of the trochlea.
- A tangent to the lateral facet of the patella.
- With the knee in 20° flexed, this angle should normally open laterally.[1]
- The patellofemoral index is the ratio between the thickness of the medial joint space and the lateral joint space (L). With the knee 20° flexed, it should measure 1.6 or less.[1]
Also, look for:
- Any resultant fractures of the patella
- Knee effusion, seen as increased space under the patella.
Report
Report even the absence of dislocation or fracture.
|
Knee effusion and mild lateral subluxation. No apparent fractures (minimal radiodensity at the medial margin probably consisting of soft tissue calcification). |
Notes
- ↑ For a full list of contributors, see article history. Creators of images are attributed at the image description pages, seen by clicking on the images. See Radlines:Authorship for details.
