The uncontrolled desire to straighten the leg is clinically classified into the following cases: 1. When walking, the knee joint is not stable in the straightened position during activities due to dysfunction and paralysis of the body muscles in front of the knee, forcing the knee to walk in the posterior extension position when carrying weight. 2. For weakness of the flexor muscles, that is, weakness of the paralyzed muscles behind the knee and relaxation of the joint capsule and ligaments behind the knee joint causing posterior extension of the knee joint. 3. The knee joint position is abnormal due to inherent bony changes. First, it occurs mostly in children with spinal cord injury or spastic cerebral palsy. Second, it mostly occurs in stroke patients and in patients with a broken flexor muscle of the knee joint and damage to the nerves that innervate the knee muscles, or due to inflammation. Thirdly, there are bony dislocations and deformities of the knee joint. If this occurs, it is necessary to go to the hospital, perform the appropriate tests, make a clear diagnosis, and give the appropriate symptomatic treatment.