Multi-Link Safety Knee
Activity Level and Body Weight Limits
|Activity Level||Body Weight Limits|
For those who use locking knees.
The SwanS is a knee joint designed for users whose activity level makes it difficult to decide whether to choose a locking knee or a freely moving safety knee.
- Preventing Knee Bending During the First Half of the Stance Phase (the Dynamic Stabilization Mechanism)
When the SwanS applies weight to the heel during full extension, the SwanS's links use bouncing bumpers to absorb the impact by displacement (slight bending). When that happens, the front and back vertical links become nearly parallel, momentarily transferring the knee joint's center of rotation toward the hip joint and preventing knee bending during the first half of the stance phase.
During the mid-phase, the displacement of the SwanS links is gradually reversed, restoring the four main links and allowing the knee to bend.
- The Bouncing Mechanism
Because the SwanS links undergo elastic displacement (slight bending of 4° or less) during the first half of the stance phase, vertical repositioning of the center of gravity is reduced, while at the same time, the body absorbs stance-phase impact from the floor, allowing it to advance forward smoothly. As a result, walking consumes less energy, and enabling a smooth gait (with double knee action) that is very close to a normal walk.
The duration, sensitivity, and volume of the bounce can be adjusted to suit the user's body weight and activity level by adjusting the inclination of the SwanS and the amount of compression by the bouncing bumper.
For those who use locking knees.
- Walking Training
- SwanS is outfitted with a small-capacity pneumatic cylinder and a strong extension assist spring. That's why, for target low-activity users and new prosthetic leg users, the SwanS basically does not bend during the swing phase. However, through walking training, users can learn, little by little, to make the knee bend during the swing phase. If you begin to walk swinging the SwanS firmly and feel that you don't have enough swing phase control, there is the possibility of upgrading to the M0780 Swan, which is fitted with a swing-phase-regulating hydraulic cylinder.
- Momentary Center-of-Rotation Repositioning for Greater Stability
- To make it possible for users who use locking knees to walk without concern, the SwanS is designed to raise its momentary center of rotation, giving it a higher degree of stability than the M0780 Swan. During bouncing, the momentary center of rotation shifts well upward. By shifting the momentary center of rotation far up, even past the hip joint axis, knee bending after heel contact can be prevented completely.
- Stability and Ease of Walking that Surpass Locking Knees
- The SwanS has been refined with a link mechanism that allows an even higher level of stability for low-activity users. It follows that bouncing during the initial stance phase is even easier. The bouncing mechanism shortens the time between heel-ground contact and sole-ground contact, and makes it possible to walk with more stability than with a locking knee, particularly when going down stairs or traversing a bumpy road.
The Constant-Friction Mechanism
The SwanS incorporates a constant-friction mechanism that only engages during knee extension, thanks to a one-way clutch. If users learn through training to bend the SwanS during the swing phase while they walk, terminal impact during full extension becomes a concern. There's a constant-friction adjustment screw that can be tightened to alleviate terminal impact in such a situation.
A Comment from the Developer
We analyzed the vector of the load sustained by the knee joint while walking with a prosthetic leg, and in order to achieve dynamic stability, we outfitted it with five links. The redundant links satisfy the difficult-to-meet conditions for achieving both safety and comfort. We worked on a design that would include functionality for "safe and comfortable walking without fatigue" as well as "gracefulness," and also kept its appearance while in the sitting position—something usually overlooked—in mind. Normalization includes users giving up the urge to hide their prostheses. We designed this knee joint with that in mind.
- he front S-shaped link prevents interference with the socket when the knee is bent. We narrowed the design of the shinbone part that connects to the bottom.
- We made no compromises with the hydraulic cylinder that cushions the rear links, cutting it from a single block of aluminum alloy to make it very strong and light-weight.
- To prevent it from pinching clothing or fingers, we fitted it internally with an extension stopper. Its overall round contours give it a friendly appearance.
Even though the users may not realize it, this product has a five-link structure with a dynamic stabilization mechanism (preventing knee bending through link geometry) and bouncing bumper that allow for safe, comfortable, worry-free walking and an attractive gait. We drew a clear line regarding traditional "hide the handicap" designs, designing instead a prostheses that was meant for showing, and we hope this will be encouraging for both users and those around them as well.
|Body Weight Limit||75 kg|
|Overall Length||164 mm|
|Overall Width||63 mm|
|Swing Phase Control Mechanism||Pneumatic Cylinder and Extension Assist Spring|
|Stance Phase Control Mechanism||Bouncing Mechanism|
|Maximum Bend Angle||150°|
The Origin of the Nickname
The SwanS is the third knee joint in the Swan series. The final S in "SwanS" stands for four words: "simplicity," "safety," "silver" (referring to elderly users), and "spring." "Spring" comes from the extension assist spring used in the swing-phase control mechanism, and "silver" because the SwanS is designed more for elderly users than the Swan is. The device also incorporates silver in its color scheme. This joint was actually based on the SL prosthetic leg, which is why its base color is silver. It might be noticed that the SwanS was discreetly designed for its target users with this in mind. While the Swan and Swan100 logos were designed with S's in the shape of swans, the SwanS logo uses a more serious lettering-only design. In fact, there were some concerns raised that the design of the Swan and Swan100 logos was too "playful." In the end, both the logo and name have been used together to promote the Swan products.