Prosthetic devices provide amputees means for having a normal quality of life. Prosthetic devices are especially beneficial for transfemoral amputees, in which their amputation extends above the knee. For these individuals, a conventional above-the-knee prosthetic device may include a lower portion, such as an artificial lower leg and foot, and an upper portion, such as a rigid socket used for securing to the amputee's residual limb. A knee joint may be used to connect the lower and upper portions, and provide mobility to an amputated leg.
An artificial knee joint is typically connected between the upper and lower portions of the above-the-knee prosthesis to swing the lower portion relative to the upper portion to facilitate walking. Conventional artificial knee joints provide the same functionality as a normal knee and may include a hydraulic system with a pneumatic or spring cylinder. These systems generate a resistance or drag force to perform the swing motion of the lower leg during walking. Some artificial knees also require an additional attachment means to connect the knee joint to either the upper and/or lower prosthesis portion.
FIG. 1 shows an example of a customary adapter for connecting an upper portion of a transfemoral prosthesis to a lower portion. Such adapters are limited because they can only provide flexion and extension to a transfemoral prosthesis, and permit no twisting motion. The ability to achieve full use of a prosthetic limb is an important factor in both the physical and mental rehabilitation of an amputee. Allowing an amputee to operate their prosthetic device as if it was a normal limb is important during both walking and sitting.
Classic single-axis prosthetic knees only allow slight swinging of the lower portion of the leg prosthesis to mimic the wearer's natural gait. However, a true recreation of the gait cycle requires more than just bending at the knee. It would also require proper flexion and coordination between the ankle and hip as well. Attempts to more closely recreate a true gait motion by altering prosthetic knees to include additional axes from which to rotate about during ambulation have resulted in dangerous conditions. Allowing the lower portion of an above-the-knee prosthesis to rotate about its longitudinal axis while walking creates the risk of twisting an attached prosthetic foot out of proper stepping alignment. This leads to an unstable and unsafe walking motion.
When an amputee walking on an uneven surface tries to stop, the amputee will fall down if the artificial knee joint cannot resist rotation. It is important to maintain both dynamic and static alignment of the lower and upper portions of the above-the-knee prosthetic device in order to properly stabilize rotation of the lower portion from the upper portion when walking or standing still.
There are other times apart from ambulation when an amputee may want to rotate the lower portion of the transfemoral prosthesis about its longitudinal axis. The ability to twist the lower portion could allow the wearer to sit cross-legged on the ground, such as in a lotus position. Conventional knee joints in above-the-knee prostheses do not permit this type of rotation since their main purpose resists such twisting to ensure a steady and predictable bending motion during walking.
It can be seen from the foregoing there are many substantial needs for improving on the drawbacks of conventional prosthetic knee adapters. The present disclosure addresses these aforementioned shortcomings.