An artificial joint including a main body and a lower portion adapted to pivotally engage the main body about a control axis while having a locking means that is integral with the lower portion. An upper portion adapted to pivotally engage the main body about a flexing axis and has an engagement means adapted to engage and disengage the locking means upon the pivoting rotation of the upper portion relative the main body. A biasing means is adapted to engage both the main body and the lower portion thereby biasing the locking means to engage the engagement means, and at least one stopping surface adapted to limit motion between the main body and the lower portion. The locking means is activated when a load is imposed on the artificial joint and passes through a line posterior to the control axis, and is de-activated when the load passes through a line anterior to the control axis.