Pain when flexing the thigh, for patients with trauma, need to consider quadriceps injury, and long-term exercise patients, such as splits, straddle wooden horse, and other actions may strain the medial retractor muscles, resulting in pain in the inner and proximal thigh. For patients without trauma, it is necessary to exclude hip flexion pain caused by diseases of the hip joint itself, commonly including hip impingement, sciaticofemoral impingement, acetabular labral injury, hip dysplasia or acetabular over-inclusion. Early stage of femoral head necrosis may also be accompanied by pain in hip flexion. For this group of patients, plain radiographs and magnetic resonance examinations can be evaluated, and arthroscopic surgical treatment is needed if necessary.