Improving Knee Extension with a Resistance Band . In this video, the resistance band is helping to mobilize the knee joint into extension — one of the key movements for walking normally after surgery or injury. . As the person shifts their body weight forward and back, the band gently pulls the lower leg into a position that encourages posterior glide of the tibia (the shin bone). . That glide is what allows the knee to fully straighten — something that’s often limited early after surgery or whe