The third compartment of the knee: an update from diagnosis to treatment.

The anterior part (third space) of the knee appears important in the soft tissue functional outcome following knee replacement surgery. Native patellofemoral kinematics are complex and variable, and further understanding has led to prosthetic redesign. Attention to soft tissue tension anteriorly (balancing the third space) during knee replacement may maximise post-operative function and avoid issues with understuffing and overstuffing. Patellofemoral compression forces may now be measured dynamically during knee replacement, allowing an objective approach to balancing the third space.