Two cases of dorsal defect of the patella with arthroscopically visible cartilage surface perforations

Radiographic/MR Imaging Correlation of the Pediatric Knee Growth

Normal bone growth of the pediatric knee as well as normal variants of ossification result in different appearances that can be identified on imaging (radiography/MR imaging). Familiarity with these changes is important to avoid confusing normal growth with pathology. This article illustrates the main features related to normal bone growth (growth arrest lines, physeal changes, ossification centers within the epiphysis, hematopoietic marrow within the metaphysis) and physis disappearance (« FOPE »). Variants in femur (epiphyseal irregularities, subchondral anomalies of posterior condyles, periosteal desmoid), tibia (tibial tuberosity ossification), and patella (dorsal defect, bipartite patella, lower pole fragmentation) are also described.

Successful conservative management of symptomatic bilateral dorsal patellar defects presenting with cartilage involvement and bone marrow edema: MRI findings

The dorsal patellar defect is a relatively rare entity that involves the superolateral quadrant of the patella. It is usually considered to represent a delayed ossification process, although its exact origin remains unclear. Because of its usually innocuous nature and clinical course, invasive interventions are generally deemed unnecessary, although curretage has been successfully performed on symptomatic cases. This case report presents a rather unusual case of symptomatic bilateral dorsal patellar defects with cartilage involvement and widespread surrounding bone marrow edema as demonstrated by magnetic resonance imaging (MRI). Both cartilage involvement and bone marrow edema should be considered part of the spectrum of associated MRI findings that can be encountered in this entity. Furthermore, the presented case shows that symptomatic dorsal patellar defects can be treated conservatively with success and that (decrease of) pain symptoms are likely related to (decrease of) bone marrow edema.

Dorsal defect of the patella with fracture in a teenager

We report the case of a young boy who presented a dorsal defect of the patella (DDP) with fracture after a small sport trauma. The patient's parents (professional of health care) had been warned on a possible tumoral disease in a previous consultation and claimed for an accurate diagnosis. Although fracture is rarely reported in DDP, the radiographic image strongly suggested this condition; nevertheless, the diagnosis accuracy requested by the parents lead to indicate a biopsy that showed irregular fragments of laminar bone and hyaline cartilage islands similar to articular cartilage compatible with a non-specific developmental ossification defect. The lytic defect was filled with morselized cancellous bone graft, the fracture having a normal consolidation. With a follow-up of 4 years, the patient is asymptomatic, and the radiological morphology of the patella is normal. Although DDP is accepted to be a radiologically well-defined condition, images may perhaps not get accuracy enough for diagnosis and biopsy may be indicated by clinical and radiological features different than the typical ones. Although fracture is rarely reported in case of DDP, it has not to be considered as indicative of tumor or malignancy.