The NEURO LOCK H2O system knee joint is a locked joint which is dirt- and water-resistant thanks to its robust, carbon fibre-reinforced joint case. It provides motion control and is preassembled in a physiological joint angle of 5°. It can be unlocked via a lock lever. With this lock lever and the use of a fixing pawl, the system joint can be permanently unlocked. Furthermore, the NEURO LOCK H2O system knee joint can be functionally converted into a NEURO CLASSIC H2O system knee joint by removing the locking pawl, the spring guide and the pressure spring.