Rank the following knee types from least stable to most stable: outside hinges, single axis knee, weight activated friction control, polycentric.

The ranking of knee types from least stable to most stable is based on their design and function during gait and weight-bearing activities.

Outside hinges are typically the least stable of the options listed. This knee type does not provide intrinsic stability and relies heavily on external control from the user or the structure of the orthotic device. They allow for basic movement but can be prone to collapse, especially in scenarios with uneven terrain or during rapid movements.

The single axis knee provides more stability compared to outside hinges. This type utilizes a fixed pivot point which allows for controlled flexion and extension. While it is more stable than outside hinges, it still lacks advanced mechanisms to adapt dynamically to shifting loads and gravitational forces as seen in more complex knee designs.

Weight activated friction control mechanisms take stability a step further. This design utilizes the user's weight to engage friction, allowing for a more controlled descent during flexion and providing resistance when the knee is weight-bearing. This results in improved stability during loading but may not fully adapt to changes in movement patterns or terrain without user adjustments.

Polycentric knees are the most stable among these options. The polycentric design features multiple pivot points, allowing for a more natural gait. The changing center of rotation provides better control during flexion and extension and can