Management of Extensor Mechanism Injuries Following Total Knee Arthroplasty

Extensor mechanism complications following total knee arthroplasty (TKA) can markedly impact the outcome and impair the patient's functional activity. These complications range from patella instability, patella fracture, and rupture of the patella tendon to rupture of the quadriceps tendon. They may arise from various causes, such as surgical technique, implant design, or patient factors, including traumatic injury.

Patella instability is probably the most reported complication following TKA and has been implicated in femoral and tibial component malalignment or malrotation, along with soft-tissue imbalance. It is important that the treatment strategy addresses the underlying etiology. The best way to avoid patella instability is to pay attention to component position and soft-tissue balancing during the index TKA.

Patella fractures are relatively rare but are the second most common periprosthetic fracture following femoral fractures and may be associated with disruption of the extensor mechanism or loosening of the patellar component. While some fractures can be successfully managed nonoperatively, displaced fractures with disruption of the extensor mechanism with a loose patellar component require surgical intervention. To achieve optimal outcomes, it is recommended that the fracture be classified based upon the integrity of the extensor mechanism, quality of the bone, and stability of the patellar component.

Ruptures of the patellar tendon following TKA are devastating injuries that are challenging to treat. The best treatment for these injuries is prevention; however, when surgery is necessary, utilizing extensile approaches is important when the exposure is difficult. When injuries do occur, operative intervention is chosen based on the acuity, location of disruption, and status of the residual soft tissues.

Like rupture of the patellar tendon, quadriceps tendon ruptures following TKA represent a challenging complication with potentially severe consequences. Management of these injuries is based upon the extent of injury and the patient's ability to maintain active knee extension with a minimal extensor lag. When nonoperative treatment is not an option, there are multiple operative alternatives, from direct repair to structural augmentation, based upon the quality and integrity of the residual quadriceps tendon.

In this special issue of the Journal of Knee Surgery, the following articles will review each of these specific topics and provide the reader with greater insights into the management of extensor mechanism injuries following TKA.

Publication History

Article published online:
16 October 2025