Fact-sheet: Femoropatellar dislocation
Updated on 04/23/2019 at 10:01 AM
View all RADEOS cases associated with this fact-sheet
Definition
Dislocation between the patella and the femoral trochlea
Classically affects adolescents and occurs during athletic activity in two-thirds of cases.
Predisposed by femoropatellar dysplasia, with a risk of recurrence.
Clinical features
Diagnosis is straightforward if the patella is still dislocated at the time of examination, or in cases of spontaneous reduction.
Patellar ballottement sign related to an intra-articular effusion
Pain at the medial aspect of the patella
Functional impairment
Radiography
Radiographs: AP, lateral, and 30-degree axial patellar view
- Patellar dislocation if not reduced
- Fracture of the patella or lateral femoral condyle
- Bony avulsion
- Intra-articular effusion
- Femoropatellar dysplasia
Ultrasound
Intra-articular effusion
Thickening of the patellar retinacula
CT
May be performed to look for a fracture.
MRI
Intra-articular effusion
Mirror-image bone marrow edema of the medial patellar facet and the lateral femoral condyle, hyperintense on PD sequences
Cartilage lesion and subchondral fracture with a T1 hypointense line
Intra-articular loose bodies related to an osteochondral avulsion
Management
Reduction of the dislocation
Orthopedic treatment: bracing and early rehabilitation with selective muscle strengthening (vastus medialis)
Surgical treatment:
if there is a fragment or osteochondral lesions
anatomic correction of the dysplasia
