How does cementless knee fixation rely on bone ingrowth, and what patient factors influence outcomes?

• A. Provisional press-fit and porous surface allow osseointegration; bone quality, activity level, and proper alignment influence outcomes; osteoporosis lowers fixation.
• B. Cementless uses cement.
• C. Osseointegration is not needed.
• D. Only age matters.

Answer: (A)

Cementless knee fixation relies on a stable initial press-fit and a porous surface that invites bone to grow into the implant, creating a durable biological attachment called osseointegration. The porous coating provides a scaffold for new bone to interlock with the implant, so long-term stability comes from bone ingrowth rather than cement. How well this works depends on the patient: good bone quality supports robust ingrowth, while osteoporosis or poor bone stock weakens fixation and raises the risk of loosening. The amount and pattern of loading matter too—adequate, controlled activity after surgery stimulates bone remodeling and ingrowth, whereas excess micromotion or misalignment can interrupt the process. Proper alignment ensures even load distribution at the bone-implant interface, which supports successful osseointegration. In short, the initial press-fit plus a porous surface enable bone ingrowth, and outcomes are influenced by bone quality, activity level, and correct alignment.