Presentation
Recurrent patellar dislocation with twisting injury.
Patient Data
Patellar evaluation
Reduced trochlear depth (3mm) with a borderline increased TT-TG distance of 18 mm
Menisci
Medial meniscus: ramp lesion with reduced volume of posterior horn
Lateral meniscus: intact
Ligaments
Cruciate ligaments: partial-thickness tear of ACL with mild mucoid degeneration. Intact PCL.
Medial collateral ligament: superficial and deep components intact. No periligamentous edema.
Lateral collateral ligament: intact
Posterolateral corner structures: intact
Extensor mechanism
The distal quadriceps and patellar tendons are intact. Lateral translation of the patella with partial disruption of the medial patellofemoral retinaculum at patellar attachment
Fluid
Gross suprapatellar effusion with a fluid level suggestive of blood within. No Baker’s cyst.
Osseous and articular structures
Bones: bony contusion of the medial margin patella and lateral margin lateral femoral condyle due to recurrent patellar dislocation.
Patellofemoral compartment: no hyaline cartilage disease.
Medial compartment: no hyaline cartilage disease.
Lateral compartment: no hyaline cartilage disease.
Case Discussion
Morphometric measurements document the trochlear dysplasia that results in recurrent patellar dislocation. Secondary marrow edema of the medial patellar margin and the lateral femoral condyle is associated with other internal derangements, including a partial ACL tear.
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