The lateral thigh depression may be related to the following causes: 1. There may be muscle atrophy here. This condition is often seen in cases of muscle paralysis due to local nerve damage, or disuse muscle atrophy. The former is often due to nerve damage resulting in malnutrition of the muscles here, followed by atrophy. The latter is often due to prolonged bed rest or braking, resulting in insufficient exercise and stimulation of the muscles here, which in turn produces atrophy. 2, there may be long-term pressure. There are many patients, especially female patients, who often like to cross their legs when sitting or standing, or have other poor posture. These poor postures may cause long-term pressure here, and over time may cause depression here. 3, may be the deformity caused by old injury. If there is a large area or deep soft tissue loss or a deformity caused by a serious femur fracture, it may cause a concave situation here.