Comparison of 8-year knee osteoarthritis progression in 2 siblings: a case-based review.

Because the pathophysiology of knee osteoarthritis is poorly understood, optimal evidence-based clinical management is uncertain. Sibling comparison studies can help inform a clinical model to guide preventive care. We compared the 8-year clinical outcomes in 2 sisters with a family history of osteoarthritis, normal BMI, and absence of knee pain at baseline. Both patients had Kellgren-Lawrence grade 1 in the affected knee at the time of twisting knee injuries leading to osteoarthritis diagnoses at age 50 (patient 1) and 51 (patient 2). Patient 1 developed a chronic right knee effusion, and progressed to Kellgren-Lawrence grade 3 bilaterally by the time she had a right total knee replacement at age 58. Patient 2 had subchondral fractures of the right knee with transient effusion, which healed after 1 year of partial weight-bearing with crutches and subsequent daily use of knee sleeves. Patient 2 had Kellgren-Lawrence grade 0 bilaterally upon surveillance imaging at age 58. The terms "osteoarthritis and knee and diagnostic imaging and subchondral bone and pathophysiology" were searched in the PubMed database to identify original research articles to inform a clinical model consistent with the patients' outcomes. A fluid model of osteoarthritis was the best explanatory model for the discordant clinical trajectories of the age-matched siblings. Patient recommendations are presented based on these findings.