Jain et al used an algorithm to guide management of a patient with a primary patellar dislocation. The authors are from Southern California Permanente Medical Group in San Diego.


Patient selection: first time patellar dislocation


Initial workup:

(1) history

(2) physical examination

(3) aspiration of the knee if there is a tense effusion

(4) X-rays of the knee


An MRI is performed if one or both of the following is present:

(1) there is an hemarthrosis identified on the aspirate

(2) there is a displaced osteochondral fragment seen on the X-ray


If the MRI indicates that there is a displaced osteochondral fragment or fracture:

(1) Determine the size of the osteochrondral fragment.

(2) If the fragment is large enough (subchondral bone >= 9 mm) then perform surgical repair. If the fragment is smaller then the patient can either undergo surgery or elect to be followed.

(3) Perform knee rehabilitation after recovery from the knee surgery.


If an MRI is not performed or if the MRI is negative, then:

(1) immobilize the knee in extension for 3-6 weeks

(2) followed by knee rehabilitation

Evidence of Fragment

Fragment Large Enough






large enough



not large enough

Surgery OR follow.


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