Knee revision surgery replaces an artificial knee joint (prosthesis) that has failed after an initial, or primary, total knee replacement (TKR). The initial TKR is highly successful, with most implants lasting 15 to 20 years or more. When the original implant causes persistent pain, instability, or mechanical failure, the revision procedure involves removing some or all existing components and replacing them with new ones. This surgery restores stability and function to the knee joint.
What Makes Revision Surgery Different
Revision surgery is inherently more complex and technically demanding than the original total knee replacement procedure. The surgeon must carefully remove the previously implanted components, which is challenging due to scar tissue and bone ingrowth around the old implant. This step requires specialized surgical tools and techniques not needed for a primary TKR.
Operating time is typically longer, often lasting two to three hours or more in complicated cases. The revision surgeon must address damage caused by the failed implant, including significant bone loss or compromised soft tissues resulting from the failure mechanism (e.g., infection or chronic loosening). Extensive preoperative planning is mandatory to anticipate issues and ensure specialized implants and tools are available.
Common Reasons for Total Knee Failure
The need for revision is driven by three main categories of failure that compromise joint integrity. One frequent reason is aseptic loosening, where the implant detaches from the bone without infection. This loosening often begins with the wear of the polyethylene plastic spacer between the metal components.
As the plastic wears down, microscopic particles are released, triggering a biological response. The immune system attempts to absorb these particles, leading to the destruction and erosion of surrounding bone (osteolysis). This bone loss weakens fixation points, causing the implant to loosen, resulting in pain and instability.
A second significant cause is periprosthetic joint infection (PJI), where bacteria colonize the surfaces of the artificial joint components. Though relatively rare, PJI is a serious complication that can occur shortly after the initial surgery or many years later. Treating an infection usually requires a two-stage procedure: the first surgery removes the infected components and places an antibiotic-loaded cement spacer, and the second surgery replaces the temporary spacer with a new, permanent implant after the infection is cleared.
The third major cause is instability or component malalignment, occurring when soft tissues cannot provide adequate support. If ligaments are too loose or components were not perfectly aligned, the knee can feel unstable or “give way” during activity. This lack of stability leads to excessive movement and stress, causing pain and premature wear, necessitating a revision to re-establish proper joint mechanics.
Specialized Techniques Used During Surgery
During revision, surgeons frequently encounter a deficiency in the patient’s natural bone stock due to implant failure. Specialized techniques and materials rebuild the joint foundation before the new implant is placed. Smaller areas of bone loss can be filled with morselized bone graft, which is ground-up bone tissue often sourced from a bone bank (allograft).
For larger bone voids, the surgeon may use modular metal components such as metaphyseal sleeves or cones, often made of porous tantalum. These porous metal structures fit into the bone defect, providing a stable base and encouraging the patient’s bone to grow into the scaffolding for long-term fixation. This mechanical reconstruction is crucial because standard implants cannot be fixed securely to damaged or missing bone.
When ligaments are severely compromised or destroyed, the surgeon must use implants more constrained than a standard TKR. A constrained condylar knee (CCK) implant uses a larger central post and box mechanism to provide internal stability, compensating for ligamentous insufficiency. For profound instability or complete ligament failure, a rotating hinge implant is necessary, mechanically linking the femoral and tibial components like a door hinge, substituting for lost soft tissue support.
Post-Operative Expectations and Rehabilitation
Recovery following knee revision surgery is typically longer and more challenging than the initial total knee replacement. Because the procedure involves more soft tissue dissection and bone reconstruction, patients expect a longer hospital stay and a slower initial recovery phase. Pain management is a coordinated effort, often requiring transition from intravenous medication to oral pain relievers.
Physical therapy must begin immediately after surgery to prevent stiffness and restore range of motion, but progress is often more gradual than after a primary TKR. Patients must adhere strictly to the physical therapy regimen, which determines the final outcome. Full recovery, including the return to most daily activities, may take six months to a year, compared to three to six months for a first-time replacement. The functional outcome, while an improvement over the failed joint, may result in a slightly reduced range of motion compared to a successful primary replacement.