KINETICS AND KINEMATICS OF A LATERAL THRUST GAIT
These biplanar and triplanar deformities lead to medial compartment arthritis of the knee as the result of an altered screw-home mechanism. Studies have shown an overall stiffening gait which exhibits a reduction in motion in the sagittal plane. Patients with osteoarthritis have shown a significant decrease in knee extension during single limb support. Additionally, they have decreased maximum flexion during swing phase. Patients who have OA had a significant increase in the knee adduction angle throughout the gait cycle. These patients also had smaller range of internal and external rotation. During stance phase, the arthritic patients maintained a neutral position whereas the normal patient's knee rotated internally. This may be due to the lack of the knee extension. Even during swing phase, the patient with OA maintained a neutral position compared to a normal knee which externally rotates during swing phase. Based on my own experience and my own opinion as a person with posterolateral corner deficiency and medial compartment arthritis, I feel that a newly designed KAFO made from my Rotation Realignment System® repositions the tibiofemoral joint to move more closely simulating the natural screw-home mechanism. This system may also benefit adult and pediatric patients with the most complicated orthotic requirements including post polio (PPS), CMT, MS, CP, SCI, stroke, arthritis, brain injury as well as infantile tibial varus (or Blount's Disease).
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Malalignment of the lower extremity identified as genuvarus (bow-legged) is the most common frontal plane alignment which leads to medial compartment arthritis. Lateral thrust is defined as an abrupt worsening of varus, which is observed while the limb is weight bearing during ambulation, with a return of the limb to a less varus alignment during swing phase or non weight bearing phase of gait. Lateral thrust is seen as a biplanar deformity or a triplanar deformity. The biplanar deformity occurs when the ankle is internally rotating, resulting in lateral thrust, which often originates as pronation and calcaneal eversion of the foot with a static virus aligned tibia. Whereas a triplanar deformity occurs when the ankle is externally rotating, resulting in lateral thrust and recurvatum. The triplanar deformity is also know as a posterolateral corner deficiency. These deformities which usually lead to medial compartment arthritis may be caused by a number of pathologies such as stroke, trauma, spinal cord injury or polio to name a few.
Varus lateral thrust is observed while the limb is weight bearing during ambulation.
