Femoroacetabular impingement syndrome is recognized as a major cause of hip pain and acetabular labral tears in young adults. Although a number of authors have documented improvements in hip joint range of motion and clinical symptoms after arthroscopic surgery161718192021), this is not always the case. There are some reports in the literature describing unsatisfactory improvements in hip joint range of motion and clinical symptoms, most often as a result of impingement remaining due to inappropriate decompression and arthroplasty after surgery2223). Recent studies have reported that hip impingement syndrome may be caused by extra-articular impingement, in particular, AIIS impingement, in patients without improvement in symptoms after surgery242526). AIIS impingement is categorized into three morphological variants according to the AIIS classification system proposed by Hetsroni et al.25) (Table 1). Patients with AIIS impingement during hip flexion experienced pain in the distal end during flexion and internal rotation of the hip. These symptoms improved with bump resection in the AIIS 242526). Previously, open reduction using the Smith-Peterson approach was used; however, a minimally invasive approach can now be attempted using advanced hip arthroscopy techniques27). The authors presented a case showing symptom improvement following arthroscopic decompression (Fig. 1). It is important to note, however, that a number of precautions are recommended when performing arthroscopic resection of the AIIS. For instance, since the AIIS is the origin of the direct head of rectus femoris, excessive excision during arthroscopic decompression may lead to rectus femoris injuries and a decrease in knee extension strength. Interestingly, Hapa et al.28) suggested that: i) these risks are lower because the rectus femoris does not attach to the anteromedial AIIS, and ii) injuries significant enough to induce a decrease in hip flexion strength are less likely to occur because the rectus femoris attaches to the AIIS extensively when an additional incision is made at the proximal and lateral aspects. Regardless of the variances in the perceived risk of this approach, surgeons should be cautious about proceeding with surgery.

Snapping hip syndrome may be due to external or internal causes and is thus characterized as either “internal” or “external” snapping hip. Internal snapping hip is associated with pain and an audible snapping sound as a thickened iliopsoas muscle travels across the anterior aspect of the femoral head, joint capsule of the hip, or iliopectineal eminence. In hip arthroscopy, the anterior, anterolateral, and posterolateral portals are considered standard options. After insertion of the arthroscope through the anterolateral portal, the iliopsoas tendon can be exposed through incision over the anterior joint capsule via the anterior portal. Iliopsoas tendon release can be done arthroscopically. During this procedure, care must be taken to avoid injury to adjacent neurovascular structures. Internal snapping hip may also result from the protrusion of an acetabular cup, formation of abnormal angle of the iliopsoas tendon, and excessvie femoral anteversion after total hip arthroplasty293031). We achieved satisfactory results in improving the symptoms of internal snapping hip by performing arthroscopic iliopsoas release in a patient who complained of persisting pain at the anterior aspect of the hip after receiving total hip arthroplasty due to avascular necrosis (Fig. 2).

External snapping hip is accompanied by a snapping noise associated with a thickening of the iliotibial band as the iliotibial band slides over/catches on the greater trochanter during hip extension from a flexed position. This syndrome is often associated with inflammation and tenderness in the greater trochanteric bursa. Asymptomatic snapping hip resolves spontaneously and when accompanied with pain typically resolves with conservative treatment. Surgical management is implemented only when conservative treatment fails32). Resection of the greater trochanteric bursa and iliotibial band release can be attempted with an open procedure3334), and favorable outcomes have been reported using an arthroscopic procedure3536). Arthroscopic removal of the bursa can be performed to manage greater trochanteric pain syndrome accompanying chronic inflammation in the greater trochanteric bursa. A 30° angled arthroscope was placed in the inferior portal (viewing portal) by making portals 3 cm distal and 3 cm proximal to the tip of the greater trochanter, and the iliotibial band was released by inserting radiofrequency probes via the superior portal (working portal) (Fig. 3).

Deep gluteal syndrome describes the presence of sciatica arising from non-discogenic and extrapelvic entrapment of the sciatic nerve37). Structures involved in sciatic nerve entrapment within the gluteal space include the piriformis muscle3839), fibrous bands containing blood vessels and gluteal muscles40), hamstring muscles4142), the gemelli-obturator internus complex4344) and others. Recently, the term ‘deep gluteal syndrome’ is preferred over ‘piriformis syndrome’. Differential diagnosis of deep gluteal pain is essential to discriminate from hip pain arising from the vertebral column. For this reason, history taking and physical examination are crucial. Patients should be assessed for: i) radiating pain to the lower limbs, ii) abnormal nerve sensations, and iii) abnormal nerve reflex and muscle weakness in the sciatic nerve; importantly, taking a sitting position in a chair is often reported to be associated with sciatic nerve entrapment in piriformis muscle404546). Upon physical examination, active piriformis test and seated piriformis test can be carried out. Injection of local anesthetics and steroids has been described to be effective and physical therapy can be performed39). Surgical measures can be implemented when the condition does not improve with conservative treatment, and open procedure or arthroscopic surgery can be considered. Martin et al.40) and Dezawa et al.47) documented symptom improvement following sciatic nerve decompression using arthroscopy in patients with deep gluteal syndrome, and we ourselves have reported symptom improvement following arthroscopic decompression in a patient with this syndrome caused by cysts surrounding the sciatic nerve48). Therefore, radiological diagnosis (e.g., magnetic resonance imaging and other imaging tests) is required to examine soft tissues along the sciatic nerve in cases of persistent nondiscogenic sciatica of unknown genesis. Intra-articular abnormalities should be checked because paralabral cysts resemble the clinical manifestations of perineural cysts as increased intra-articular pressure is placed on the sciatic nerve (articular synovial theory)49). The authors used triangulation based on fluoroscopy-guided radiographs by creating additional portals along the upper part of, and 5 cm distal to, the posterior greater trochanter and by placing patients in a semiprone position. Cystostomy was conducted using basket forceps after confirming the sciatic nerve and adjacent cysts with unaided eyes, and symptoms improved in all cases (Fig. 4).