The inability to cock the leg may be caused by hip joint disease, lumbar spine disease, knee joint disease, trauma and other reasons. 1. Hip diseases: such as femoral head necrosis, hip dysplasia, acetabular labral injury and other diseases lead to hip joint internal rotation, internal retraction obstacles, the patient may appear the legs up. 2. Lumbar spine disease: it is common for lumbar intervertebral disc herniation to compress the nerves of the lower limbs, and the patients will have pain, numbness and weakness of the lower limbs, which will cause the patients to have the inability to cock their legs up. 3. Knee diseases: common in advanced knee osteoarthritis, the patient’s knee joint stiffness, deformity, can not complete the normal bending, internal rotation and other actions, the patient can appear to the legs up. 4. Trauma: due to trauma caused by lower limb bone, muscle and other injuries lead to patients’ activities are limited, patients can also appear Erlang leg up. It is recommended to consult a doctor in a timely manner, with the help of a doctor to clarify the cause of the disease, and to carry out targeted treatment or treatment. In addition, crossing the legs is not a good habit, easy to lead to poor posture, the knee joints, hip joints are also unfavorable, it is not recommended to cross the legs.