Subacromial impingement is an important cause of shoulder pain,which is common in orthopedic diseases. Clinicians have different views on the diagnosis and therapies. This article summarizes research advances of subacromial impingement syndrome in pathogenesis,types,clinical manifestation,ima-ging findings and treatment,hoping to standardize the diagnosis and treatment.

The infrapatellar fat pad(IFP),also known as the Hoffa's fat pad,is an intracapsular, extrasynovial structure that fills the anterior knee compartment,and is richly vascularized and innervated. It involved knee joint biomechanics,damaged cells repairing and some other processes.Factors such as trauma or operation lead to pathological changes,including fibrosis,edema,and inflammation,and finally result in disorder syndrome.IFP was discovered and named by German surgeon Albert Hoffa in 1904.It is one of the main causes of knee pain under the patellar.Clinically,it is mainly diagnosed by physical exam-ination and MRI.Treatments include physical therapy,local anesthetics,arthroscopic resection,etc.