Subchondral Insufficiency Fracture in the Non-weight-bearing Portion of the Lateral Femoral Condyle Treated with Total Knee Arthroplasty:

We aimed to report an unusual case of a subchondral insufficiency fracture that occurred at the non-weight-bearing portion of the lateral posterior femoral condyle (LPFC). An 82-year-old woman with severe knee pain was diagnosed with a subchondral bone defect in the non-weight-bearing portion of the LPFC. The patient underwent total knee arthroplasty with an intramedullary stem and an augmentation block. Twelve months post-operatively, her Knee Society score and knee injury and osteoarthritis outcome score improved from 34 to 92 and 136 to 316, respectively. Reports on subchondral insufficiency fractures at the portion are extremely limited. No surgical treatments or histological reports on subchondral insufficiency fractures at the portion have been published. In our case, pre-operative valgus alignment and a combination of factors, including sex, low bone mineral density and physical activity, and lifestyle, might have resulted in the subchondral insufficiency fracture at the location.