Atrophy below both knees is considered to be related to wasting muscle atrophy, spinal cord injury and intracranial lesions. 1. Wasting muscle atrophy: if the lower limbs do not carry out relevant exercise activities for a long time, it will cause muscle wasting atrophy, such as lower limb fracture, knee injury, etc. need long time braking, bed rest, etc., and do not carry out the functional exercise on time, the muscles below the two feet and knee joints can be atrophied. 2. Spinal cord injury: when spinal cord injury occurs, the nerves of the lower limbs can be involved, and the nerves can not play a nutritive role, which will also cause atrophy of the muscles innervated by the same, so it can be manifested as the atrophy of the foot and the lower part of the knee joint. 3. Intracranial lesions: intracranial vascular embolism or intracranial hemorrhage and other diseases can lead to motor nerve disorders of the lower limbs, muscle atrophy below the knees because of lack of nerve nutrition. When there is weakness or even atrophy below the knees, you should consult a doctor as soon as possible to clarify the cause and standardize the treatment under the doctor’s guidance.