A 31-year-old woman with known Larsen syndrome presented with congenital chronic luxation of her right knee with increasing instability symptoms, which limited her daily activities. We refrained from a constrained knee arthroplasty due to her relatively young age and decided to perform a knee arthrodesis. Knee arthrodesis is a viable lifelong-lasting operative treatment alternative for specific instability-related knee disease. The knee arthrodesis was performed by double plating with an additional fixation of the patella. At 1-yearfollow-up, she was able to walk without limitations and did not experience any pain with complete consolidation of the arthrodesis. At 2-year follow-up, she performed all her daily activities without limitations. Both the Knee injury and Osteoarthritis Outcome Score (KOOS) and the International Knee Documentation Committee subjective knee form (IKDC) improved at 2-year follow-up (KOOS: 61.3; IKDC: 56.3) compared with 1-year follow-up (KOOS: 52; IKDC: 40.2).