Sitting leg numbness can occur in all patients who sit or stand for long periods of time. However, this symptom may be caused by the following reasons in addition to prolonged sitting and standing: 1. For example, some patients are accustomed to cross their legs when sitting or standing, or overflex their knees when sitting or standing, and make their feet step on the bench or chair bilaterally. This poor posture will lead to poor blood circulation in the lower extremities, and over time there will be a series of symptoms such as cold, purple, and numbness in the lower extremities. 2. This condition may be caused by vascular lesions in the lower extremities. For example, if the patient has a large blood vessel embolism in the lower extremities, or even complete occlusion, then even if the patient sits for a relatively short period of time, it may cause numbness in the lower extremities due to poor blood circulation. 3, this condition may be caused by some peripheral nerve lesions. For example, in the case of lumbar disc herniation or sciatica, the nerve roots may be stimulated, resulting in numbness of the legs when the patient is sitting or standing. 4, this condition may also be caused by long-term pressure. For example, when the patient is sitting or standing, the prolonged pressure on a certain part of the lower limb will cause ischemia here, which in turn will produce numbness.