K1 a typical household ambulator: Has the ability or potential to use a prosthesis for transfers or ambulation on level surfaces at a fixed cadence

K1 components – Patient will require more external stability from a prosthetic device due to decreased inherent balance control
Feet – SACH (solid ankle cushion heel) or single axis
Knee – Single axis knee, braking function and locking lever

K2 Limited community ambulator. Has the ability or potential for ambulation and can traverse low-level environmental barriers such as curbs, stairs, or uneven surface. Will not be able to vary cadence. Will likely require as assistive device most of the time if not all of the time.

K2 Components – patients are somewhat more mobile but still require some external
Stability from components
Feet: Multi-axial (not carbon)
Knees: Can have weight activated stance control, non-variable resistance
mechanical polycentric knee can be locked when standing, higher ground clearance, can add flexion or extension
Single axis knee, braking function and locking lever

K3 Unlimited community ambulator. Has the ability or potential for ambulation with variable cadence and to traverse most environmental barriers. Will not require an assistive device. Activity level demands prosthetic use beyond simple locomotion.

K3 components ; patients are capable of normal activity levels so need components that are responsive and allow negotiation of all potential community barriers.
Feet – dynamic response
Knees – pneumatic or hydraulic methods of creating resistance
Same methods of resistance coupled with microprocessor

K4 Exceeds basic ambulation skills, exhibiting high impact and energy levels

K4 components
Feet – dynamic response
Knee – pneumatic or hydraulic methods of creating resistance – Not microprocessor