KAFOs consist of an AFO with metal uprights, a mechanical knee joint, and 2 thigh bands. KAFO can be used in quadriceps paralysis or weakness to maintain knee stability and control flexible genu valgum or varum. KAFO also is used to limit the weight bearing of the thigh, leg, and foot with quadrilateral or ischial containment brim. A KAFO is more difficult to don and doff than an AFO, so it is not recommended for patients who have moderate-to-severe cognitive dysfunction.
! KAFO: This orthosis can be made of metal-leather and metal-plastic or plastic and plastic-metal. The metal design includes double upright metal KAFO (most common), single upright metal KAFO (lateral upright only), and Scott-Craig metal KAFO. The plastic designs are indicated for closer fit and maximum control of the foot, including supracondylar plastic KAFO, supracondylar plastic-metal KAFO, and plastic shells with metal uprights KAFO.
- A double upright metal KAFO: This is an AFO with 2 metal uprights extending proximally to the thigh to control knee motion and alignment. This orthosis consists of a mechanical knee joint and 2 thigh bands between 2 uprights.
- A Scott-Craig orthosis consists of a cushioned heel with a T-shaped foot plate for mediolateral stability, ankle joint with anterior and posterior adjustable stops, double uprights, a pretibial band, a posterior thigh band, and knee joint with pawl locks and bail control. Hyperextension of the hip allows the center of gravity falling behind the hip joint and in front of the locked knee and ankle joint. With 10° of ankle dorsiflexion alignment, it allows a swing-to or swing-through gait with crutches. This orthosis is used for standing and ambulation in patients with paraplegia dueto spinal cord injury (SCI).
- The supracondylar plastic orthosis uses immobilized ankle in slight plantar flexion to produce a knee extension moment in stance to help eliminate the need for a mechanical knee lock. This orthosis also resists genu recurvatum and provides mediolateral knee stability.
- A plastic shell and metal upright orthosis consists of a posterior leaf spring AFO with double metal uprights extending up to a plastic shell in the thigh with an intervening knee joint.
- Knee joints: The mechanical knee joint can be polycentric or single axis. Polycentric is used for significant knee motion, and a single axis is more common and is used for knee stabilization. Single axis knee joints include the following:
- Free motion knee joint: This joint has unrestricted knee flexion and extension with a stop to prevent hyperextension. The free motion knee joint is used for patients with recurvatum but good strength of the quadriceps to control knee motion.
- Offset knee joint: The hinge is located posterior to the knee joint and ground reaction force; thus, it extends the knee and provides great stability during early stance phase of the gait cycle. This joint flexes the knee freely during swing phase and is contraindicated with knee or hip flexion contracture and ankle plantar flexion stop.
- Drop ring lock knee joint: The drop ring lock is the most commonly used knee lock to control knee flexion. The rings drop to unlock over the knee joint while the knee is in extension by gravity or manual assistance. This type of joint is stable, but gait is stiff without knee motion. A ball bearing on a spring can be added just above the drop lock to keep it from slipping up as the patient ambulates. Patients over 120 pounds usually feel more secure with both medial and lateral drop locks.
- Pawl lock with bail release knee joint: The semicircular bail attaches to the knee joint posteriorly, and it can unlock both joints easily by pulling up the bail or backing up to sit down in a chair. A major drawback is the accidental unlocking while the patient is pulling his or her pants up or bumping into a chair. Adjustable knee lock joint (dial lock): The serrated adjustable knee joint allows knee locking at different degrees of flexion. This type of knee joint is used in patients with knee flexion contractures that are improving gradually with stretching.
- Ischial weight bearing: Most individuals in a KAFO sit partially on the upper thigh band unless the cuff is brought up above the ischium.
Knee cap and strap: The knee cap can be placed in front of the knee in the orthosis to prevent flexion of the knee. A medial strap is used for genu valgum and a lateral strap is used for genu varum. These buckles wrap around the upright in the same way as ankle straps.
Plastic shell and metal uprights moldedknee-ankle-foot orthosis with drop lock joints.
Offset knee joint knee-ankle-foot orthosis.