Medial Collateral Ligament Rupture in Medial-Pivot Total Knee Arthroplasty

: A medial collateral ligament (MCL) rupture is an uncommon yet significant complication following total knee arthroplasty (TKA), potentially resulting in instability and accelerated prosthetic wear, particularly after medial-pivot total knee arthroplasty (MP-TKA). Complete ruptures are typically managed with direct repair, ligament reconstruction, or revision to a more constrained prosthetic implant. The primary objective is to restore knee stability while maintaining implant durability. We report the case of a 72-year-old woman with sarcopenic obesity who sustained an MCL rupture following MP-TKA performed for valgus knee osteoarthritis. The patient was successfully treated with revision to a more constrained prosthesis. MP-TKA relies on medial compartment congruency and soft-tissue integrity, particularly that of the MCL, to ensure joint stability and restore normal knee kinematics. This case highlights the management of MCL failure after MP-TKA in a patient with sarcopenic obesity. Revision to a constrained prosthesis may represent the most appropriate treatment option.