The author reported 20 cases of this disease in 1978, when it was called injectable gluteus maximus contracture. According to the observation of 246 cases in the PLA General Hospital, it was confirmed that the muscles that contracted after injection were not only limited to the gluteus maximus, but also involved the gluteus medius and gluteus minimus in some cases. Therefore, this disease is more appropriately called injectable gluteus contracture. Pathology and pathophysiology】 The main pathological changes are fibrous scarring in the upper part of the gluteus maximus muscle tissue, and the muscle tissue is completely replaced by fibrous scar tissue. The lesion involves an area about 2-7 cm wide, and the depth involves the whole muscle layer. The boundary between the fibrous contracture zone and the normal muscle is unclear and uneven. The direction of the fibrous contracture zone was identical to that of the gluteus maximus fibers. The above pathological changes were typical of the majority of cases, and with the increase of treated cases, some atypical pathological changes were also found. According to the surgical findings of 246 cases of gluteus maximus contracture in the PLA General Hospital, in 4 cases, the muscle fiber contracture lesion involved almost the entire gluteus maximus muscle, and it was difficult to distinguish the boundaries of the contracture zone. In 11 cases, the contracture of the gluteus medius muscle alone, in 5 cases, the contracture of the gluteus minimus muscle was combined, and in 11 cases, thickening of the gluteus fascia was found without serious pathological changes in the gluteus maximus muscle itself. It is worth mentioning that in three cases, the sciatic nerve was found to be adherent to the contracted gluteus maximus muscle, resulting in the dislocation of the sciatic nerve in the gluteal segment. According to the author’s autopsy observations, the standard gluteal muscle injection site is the outer upper quarter of the gluteus maximus, also known as the outer upper quadrant. This area is the upper part of the gluteus maximus muscle, and if the gluteal intramuscular injection is performed correctly and the needle penetration depth is appropriate, there is no doubt that the drug will be injected into the gluteus maximus muscle. In animals and cadavers, the author also observed that the drug injected into the muscle was diffused along the direction of muscle fiber travel, rather than in a circular pattern to the surrounding area. This is the reason why the contracture of the gluteus maximus always appears as a bundle in the same direction as the muscle fibers and not as a mass. Any injectable agent is irritating, but the degree of irritation to human tissues varies due to the different molecular structures and molecular group sizes of drugs. Penicillins, especially benzyl alcohol as a solvent, although it has a temporary local analgesic effect, the solvent has a strong irritating effect on muscle tissue. Repeated multiple injections can cause local chemical inflammation, followed by mechanization, proliferation of fibrous tissue, and finally formation of fibrous scar contracture fascicles. Since the chances of receiving intramuscular injections are often equal in both buttocks, the disease is more bilateral. Etiology and pathogenesis】Injectable gluteal contracture is a medical disease, mostly occurring in childhood, caused by repeated injections of drugs into the hip muscles, and is often seen by parents of children who find that their gait is peculiar and their knees are not close together in a sitting position. After this disease was first reported in 1978 at the PLA General Hospital in China, many other hospitals have discovered this disease and published several papers. The main reasons for children receiving intramuscular antibiotics are upper respiratory tract infections, bronchitis, acute tonsillitis, and pneumonia. The age at which the highest frequency of intramuscular injections into the buttocks was received was from 1 to 5 years of age at birth, with a mean of 1.5 years, while the age at which gluteal myoclonus was found was from 1 to 11 years, with a mean of 4.9 years. The drug injected was penicillin in 68.3% of cases, of which benzyl alcohol was clearly documented as a solvent in 10 cases. Fifty-two percent of the children received two or more antibiotics intramuscularly at the same time. The number of their gluteal muscle injections was proportional to the occurrence of gluteal muscle contracture. The gait is abnormal, especially when running, both lower limbs are mildly externally rotated and abducted, and due to the limitation of hip flexion, the stride length is small, as if jumping forward, which is called “jumping gait sign”. 2, pointed hip sign When standing, both lower limbs cannot be completely close together and are mildly externally rotated. Due to the contracture of the upper gluteus maximus muscle, the muscle volume is reduced, and the relative appearance of the hip is sharp, which is called the “sharp hip sign”. 3, the knees are separated when sitting, the knees are separated, not close together, not stretched “two-legged”. 4.Circular sign and frog-leg sign There are two kinds of signs when squatting: some patients show that during squatting, when the hip joint is flexed nearly 90°, hip flexion is limited and cannot squat completely, then both knees flash outward, and after an arc, both knees can come together and squat completely. Another part of the patients showed that the hips were abducted and externally rotated when squatting, and the knees were separated, and the symptoms were like the hind limbs of a frog in flexion, the former sign was called “circle sign” and the latter was called “frog leg sign” (Figure 1). These two different clinical manifestations are due to the different degree and extent of the lesion. The latter lesion is often more severe and extensive than the former. 5.Hip popping When flexing and extending the hip joint, there are cords sliding across the surface of the greater trochanter of the femur and producing a popping sound. 6.Contracture band A contracture band in the same direction as the gluteus maximus fibers can be felt at the hip, which is more obvious when the hip joint is internally rotated and internally retracted, and its width is about 2-7 cm. 7.Pelvic X-ray can be seen as “pseudo double hip valgus”, the stem angle of femoral neck is >130°, and the small femoral ridge is clearly visible. 8.Blood tests are normal, and there is no muscle disease. Treatment overview】 If hip contracture has formed, partial resection of the contracture band of gluteus maximus and partial stop release of gluteus maximus can be used. Procedure: The patient is placed on his side, and an oblique incision is made in the direction of the gluteus maximus, and the incision is turned to the top of the greater trochanter in line with the upper end of the femur. The contracture band and a section of the iliotibial bundle below the greater trochanter of the femur were exposed, the contracture band was separated, and the contracture band was cut off near the iliotibial bundle, and a 2-3 cm section of the contracture band was excised. The upper part of the gluteus maximus muscle was loosened from the tendon membrane that was connected to the iliotibial bundle to partially lengthen the gluteus maximus stop. Before the end of the operation, on the operating table, the operator should passively move the affected limb and end the operation after proving that the hip is flexed freely and there is no popping sound; otherwise, a Z-shaped lengthening of the tendon at the bony attachment point of the gluteus maximus should be considered (the gluteus maximus tendon should not be completely cut off). In the operation, the surgeon must operate in the area close to the attachment point of the gluteus maximus muscle, and must not cut the muscle in the middle part of the gluteus maximus muscle, otherwise it will cause a lot of bleeding, and it is very easy to damage the sciatic nerve. If the contracture of the gluteus maximus is found to be extensive, the sciatic nerve should be exposed before the release operation to avoid damage to the sciatic nerve. In general, bilateral surgery should be completed under a single anesthetic, and the patient’s position should be changed to re-sterilize the sheet after completion of surgery on one side. After surgery, both lower limbs are fixed together for two weeks and functional activities can be started. Usually 0.5 to 1 year after surgery completely return to normal gait. In the past 2 years, the PLA General Hospital has carried out arthroscopic release of gluteus contracture. The procedure has the advantages of less trauma, less bleeding and faster postoperative recovery. Its long-term efficacy is subject to further follow-up.