Femoroacetabular impingement (FAI) is a disorder of the hip joint that results in abnormal osseous contact between the femoral head-neck junction and acetabulum that can lead to chondral and/or labral pathology [6]. Although some individuals with radiographic FAI are asymptomatic, recurrent cyclical impingement may result in pain and discomfort among patients and is one of the predominant causes of arthritis in the nondysplastic hip [7, 8].

Ganz and colleagues pioneered the open surgical dislocation approach via a trochanteric osteotomy as an effective and reproducible technique to safely address FAI in symptomatic patients [9]. Advances in arthroscopic techniques have allowed for equivalent correction of femoral offset and focal rim impingement when compared to surgical dislocation of the hip [10]. Recent literature even suggests that arthroscopy may provide equal or perhaps greater improvement in outcomes compared to open surgical dislocation for the treatment of FAI, with a lower reoperation and complication rate [11, 12]. Arthroscopy also minimizes trauma to the periarticular soft tissues without the need for trochanteric osteotomy, which may allow for an earlier return to full activities and decreased abductor dysfunction. Although superoposterior cam and even posterior and posterior-inferior acetabular deformities can be addressed arthroscopically in expert hands, global acetabular deformities (i.e., protrusio acetabuli, acetabular retroversion) are likely better addressed through open approaches to allow for comprehensive correction of these global and extensive pathomorphologies, which may contribute to hip pain [13].

The acetabular labrum is a ring of fibrocartilage that acts as a “suction seal” to ensure continuous lubrication of the hip joint and contributes to favorable joint stability and kinematics by distributing contact forces via load sharing and deepening of the hip joint [14, 15]. Labral damage may result in painful clicking and locking, reduced range of motion, and interference with daily activities [16, 17]. Labral pathology most commonly occurs in the form of a tear and can be secondary to FAI, dysplasia, degeneration, or both major and minor trauma. During surgical treatment of labral tears, the labrum is typically debrided or repaired and/or refixed based on tear pattern and healing potential, depending on tissue quality and vascularity [18].

While labral pathology has been found to occur most commonly in the anterior and superior margins of the acetabulum, the location typically reflects the areas of mechanical conflict between femoral and acetabular pathomorphology [19]. This osseous pathomorphology must be addressed in addition to the labral damage to avoid recurrent injury and a modest clinical outcome. In the setting of acetabular dysplasia, anterosuperior, superior, and posterior abnormalities of a hypertrophic labrum have been identified [20]. The objectives of labral preservation are to treat the symptoms and pain and restore the hip seal and thus stability. Additionally, labral refixation or repair is performed with the goal of potentially preventing the premature development of arthritis associated with abnormal contact forces on the articular cartilage, which has been shown to correlate with labral tears [21]. Studies have suggested that labral repair leads to superior outcomes when compared to debridement and/or excision as part of a joint preservation procedure [22–25]. Therefore, one should attempt to repair labral tears with good-quality tissue; if this is not possible, however, labral debridement has also been shown to have good clinical outcomes [26].

The articular cartilage surfaces of the hip provide a smooth, almost frictionless articulation of the femoral head and acetabulum. Insults to the chondral surfaces can occur traumatically, both acutely from subluxation/dislocation/lateral impaction and chronically from cyclical femoroacetabular impingement (FAI) or as a result of a degenerative process, such as the static overload that occurs in dysplasia. Injury can occur on either the articular surface of the femoral head (more common with acute trauma) or on the chondral surface of the acetabulum, as is typical with FAI [1].

Chondral lesions of the acetabulum are commonly associated with intra-articular hip disorders and reflect a morphological incongruity between an aspherical femoral head-neck junction and the acetabular geometry. Loss of normal sphericity and offset at the head-neck junction, as is characteristic in the setting of FAI, can cause a delamination of the chondral surface of the acetabulum via cyclical wear. The resultant damaged cartilage can be a source of pain and mechanical symptoms. Arthroscopy allows for inspection of the chondral surfaces of the hip and identification of chondral lesions and any indicated debridement and/or marrow-stimulation techniques (e.g., microfracture or drilling) to treat these lesions [10, 27, 28]. As arthroscopic techniques evolve, whole-tissue transplantation of autograft or allograft to repair severe osteochondral defects may become possible.

Chondral lesions of the femoral head are less common than those on the acetabulum. The femoral head cartilage is thinner than the acetabular cartilage, and preparation of an adequate border for marrow-stimulation cartilage techniques is also more difficult. The success of mosaicplasty procedures in the knee has led to their application in other joints, including the femoral head [29, 30]. These procedures, however, were described via an open approach, and the application of this treatment method has yet to be described arthroscopically. As techniques continue to advance, it is likely that smaller, accessible lesions will be treated in this manner.

The risk of iatrogenic chondral injury during arthroscopy and the potential long-term consequences of such injury deserve special mention. These injuries to friable cartilage have been shown to heal poorly spontaneously, and no perfect arthroscopic treatment for smaller defects has been reported [31]. As hip arthroscopy continues to gain in popularity, great caution should be exercised by new and experienced hip arthroscopists during joint entry and surgical maneuvers to avoid creating new or exacerbating previous chondral lesions.

The ligamentum teres is a strong, intra-articular ligament that is thought to be important for the stabilization of the hip, particularly in adduction, flexion, and external rotation, the position of greatest posterior instability of the hip joint [32]. Lesions of the ligamentum teres include partial or complete traumatic tears, degenerative tears, and avulsion fractures at the foveal insertion of the femoral head [33]. Traumatic hip subluxations or dislocations have a high incidence of complete or partial tears of the ligamentum teres [34]. Chronic hip joint inflammation may also lead to degeneration of the ligament or alternatively can be indicative of hip instability [2].

Ligamentum teres injuries are difficult to diagnose and patients may present with mechanical hip pain and describe painful locking, clicking, or giving way. Arthroscopy is an effective technique that has greatly enhanced diagnosis of such injuries and is almost the single treatment modality used to resect or debride the ligament, although reconstruction techniques have been described despite limited evidence [32]. When significant tears in the ligamentum teres are encountered in the absence of degenerative change, traumatic (subluxation) and atraumatic (dysplasia/multidirectional instability) instability should be suspected. Foveal avulsions are associated with acute or repetitive hyperabduction of the hip. Classification systems of ligamentum teres injury via arthroscopic assessment have been described. Based on their arthroscopic findings, Gray and Villar [35] classified ligamentum teres tears into 3 types: type I, complete rupture; type II, partial rupture; and type III, degenerative tear. Botser et al. [36] proposed a new classification system to categorize the ligamentum teres tears, given the high prevalence of partial (type II) tears when classified according to Gray and Villar. This new classification includes grade 0, no tear; grade 1, low-grade partial tear <50 %; grade 2, high-grade partial tear >50 %; and grade 3, full-thickness tear [36].

Septic arthritis is a bacterial, viral, or fungal infection of the hip joint. The infection can cause acute chondrolysis and irreversible damage to joint articular surfaces that initially causes pain, warmth, and swelling and, if left untreated, may lead to osteomyelitis, sepsis, and eventually osteoarthritis of the joint. Septic arthritis of the hip is common in young children, in whom it is thought to be secondary to hematogenous spread of the offending agent, aided by the child’s rapid growth and robust vascularity, and in immunocompromised and elderly adults.

Open arthrotomy with adequate irrigation and debridement has been considered the standard treatment of patients with septic arthritis of the hip. Arthroscopic drainage of septic arthritis of the hip has been used as an alternative to open arthrotomy given the success that has been accomplished in eradicating septic arthritis of the knee with arthroscopic treatment [37]. Previous authors have reported case series on the effective treatment of septic arthritis of the hip with arthroscopy [38–43]. In a comparative study, El-Sayed showed equal eradication of infection at greater than 12-month follow-up with no recurrence or development of complications when comparing arthroscopic versus open treatment of septic arthritis [44]. The authors, however, emphasized early diagnosis and prompt treatment as the most important factors in successful treatment. The patients in the arthroscopic group did have a significantly shorter duration of hospital stay; however, overall recovery time was not affected by the method of treatment. Arthroscopic drainage of septic arthritis of the hip appears to be a valid alternative to an open arthrotomy, especially in cases that are diagnosed in an acute setting and in the hands of an experienced arthroscopist.

Loose bodies are small fragments of bone, cartilage, or diseased synovium that are typically mobile within the hip, either in the central or peripheral compartments. These fragments may develop as a result of trauma or from reactive bone or synovial formation due to degenerative or inflammatory processes. Loose bodies typically cause mechanical symptoms such as popping, catching, and locking [16]. Due to the variable location and composition of loose bodies, physical exam and radiological imaging are unreliable diagnostic tools. Hip arthroscopy has become a valuable tool allowing for direct visualization and treatment of loose bodies in a minimally invasive fashion [45].

A large number of small loose bodies may also be the product of primary or secondary synovial chondromatosis or osteochondromatosis. Primary synovial chondromatosis is a proliferative disease affecting the joint synovium. Synovial membrane metaplasia enlarges and typically calcifies and breaks away, thus becoming free to enter the joint compartments. Once free, the loose body typically causes pain and mechanical symptoms [46]. Secondary synovial chondromatosis is more common and typically occurs secondary to trauma. Damage to articular cartilage as a result of trauma can result in loose chondral fragments that may or may not calcify. Hip arthroscopy allows for identification and removal of these fragments and also affords the opportunity for simultaneous treatment of the damaged chondral surface [46]. Radiologic imaging, despite the use of advanced techniques such as computed tomography and magnetic resonance arthrograms, frequently fails to identify these fragments, which may consist only of cartilage, leaving arthroscopy as the best tool for their identification and removal [1].

The synovial membrane is a thin layer of soft tissue that lines the inner surface of the hip joint capsule and functions to produce and maintain the volume of lubricating joint fluid optimal for joint motion and function. The synovial lining of the hip can degenerate over time secondary to trauma, repetitive stress, and/or a variety of inflammatory arthropathies, such as synovial chondromatosis, rheumatoid arthritis (an autoimmune-induced synovial inflammation), and pigmented villonodular synovitis (PVNS, a synovial lining hypertrophy with synovial fluid overproduction).

Arthroscopy in the setting of synovial disease allows for minimally invasive treatment and also definitive diagnosis of the offending disorder. Arthroscopic synovectomy has been shown to slow deterioration of the articular cartilage and preserve hip function [45]. Focal PVNS located within the lunate fossa and inferomedial femoral neck region can be effectively treated and eradicated arthroscopically, while more diffuse disease, which commonly extends and proliferates outside the joint space into adjacent soft tissues, may warrant more thorough excision via surgical dislocation. Arthroscopy also provides an opportunity for biopsy of the synovium in a minimally invasive fashion to confirm the diagnosis of inflammatory arthropathy and guide subsequent treatment with appropriate disease-modifying agents.

Adhesive capsulitis of the hip, only recently recognized in 1999 and found to be more prevalent than previous literature indicated, is a newer indication for hip arthroscopy [47]. It is similar to adhesive capsulitis of the shoulder in that the patient experiences pain and loss of range of motion secondary to an inflammatory process of the joint capsule. However, this pathology can be nonspecific in the presence of other hip pathologies that cause pain and a decreased passive range of motion of the joint, such as FAI.

Adhesive capsulitis is likely underreported in the literature relative to shoulder adhesive capsulitis as decreased range of motion of the more constrained hip is perhaps less functionally noticeable and limiting for patients when compared to the shoulder [48]. Arthroscopy can effectively treat patients with adhesive capsulitis of the hip in a minimally invasive fashion via capsulotomy or capsulectomy of the pathologically thickened capsule and synovectomy of any associated intra-articular reactive tissue pathology.

The cause of capsular laxity and hip instability can be divided into traumatic and atraumatic etiologies. Traumatic injuries can result in capsular incompetence with or without associated labral damage. Atraumatic hip instability can be the consequence of overuse and may result in anterior subluxation secondary to repetitive external rotation with axial loading. Other individuals may be predisposed to hip instability due to general ligamentous laxity, various degrees of acetabular dysplasia, or connective tissue disorders such as Ehlers-Danlos syndrome [48, 49].

Capsular laxity, regardless of cause, can be associated with hip pain, instability, and subluxation events. Arthroscopic capsular or labral repair or reconstruction may be beneficial for patients with recurrent hip instability, particularly in the setting of prior trauma [49]. Several recent case series have proposed that the structural abnormalities associated with FAI may predispose patients to traumatic posterior hip instability and subsequent subluxation events, with one series reporting favorable outcomes with arthroscopic osteoplasty and labral refixation [50, 51]. However, these procedures should be approached with caution in atraumatic cases and primarily utilized in patients with capsular or labral insufficiency in the setting of normal bony morphology. In the setting of acetabular dysplasia, the hip is best addressed via an open procedure, such as a periacetabular osteotomy, to restore the depth, congruity, and kinematics of the joint and correct the underlying structural pathomorphology that has compromised the soft tissue envelope.

Acetabular dysplasia, the most frequently encountered form of structural instability of the hip joint, can lead to static overload of the hip and resultant pain from damage to cartilaginous surfaces, hypertrophy and degeneration of the labrum, and hypertrophy and/or tearing of the ligamentum teres [52]. Correction of a shallow acetabulum is most commonly, completely successfully addressed with a periacetabular osteotomy (PAO), which, by reorienting the acetabulum into a better fit position, improves load sharing and reduces abnormal contact forces at the acetabular rim. The PAO may be performed with an anterior arthrotomy to address any intra-articular pathology or in the setting of combined cam-morphology, but arthroscopy in conjunction with a PAO is increasingly used because it affords an opportunity for more precise diagnosis, classification, and treatment of associated intra-articular pathology [52]. A recent study by Ross et al. demonstrated that labral and chondral pathology may be as high as 86 % and 69 %, respectively, which if left unaddressed could be a potential source of residual hip pain after PAO [53].

With any level of deformity, arthroscopy can be an effective adjunct tool to a more powerful extra-articular osteotomy; however, one should be cautious when utilizing this as an isolated treatment of dysplasia because extra-articular osteotomy typically provides more definitive correction of the acetabular and femoral morphology [54]. Isolated arthroscopy in the setting of acetabular dysplasia may result in iatrogenic instability with or without bony resections, labral debridements, and capsulotomies, which have been documented on multiple occasions [55–58].

Arthroscopy in the setting of a painful total hip arthroplasty may be used to evaluate the integrity of implants, assess component wear, remove loose acetabular screws, and perform debridements of soft tissue impingement or infection [16].

There have also been reports of psoas pain and impingement after hip arthroplasty with associated component malpositioning (relative cup retroversion, oversized components, and leg-length inequalities) [59]. Definitive treatment with psoas tenotomy or component revision and tendon debridement has proven successful, but revision arthroplasty is associated with a significant rate of complications and risks, particularly in elderly patients [60]. To correct this source of impingement, psoas lengthening or release may be performed arthroscopically to reliably improve pain and function. Similar outcomes have been documented after revision hip arthroplasty and psoas tenotomy in carefully selected individuals [61]. In some cases, psoas pain has been documented without any apparent impingement. A thickened and tensioned psoas may be seen in this setting, and an arthroscopic transcapsular or lesser trochanteric lengthening can be performed [59]. A release at the level of the lesser trochanter may be more desirable due to easier exposure without the risk of iatrogenic infection or instability secondary to capsular damage required to enter the joint.

Greater trochanteric pain syndrome (GTPS) is an entity encompassing several pathologies that cause chronic lateral hip pain in the region of the greater trochanter [5]. GTPS is relatively common, reportedly affecting up to 10–25 % of the population [62]. Trochanteric bursitis is the most common form of GTPS and involves inflammation of the bursa between the trochanteric facets and the gluteus medius, the gluteus minimus, and the iliotibial band caused by repetitive trauma, commonly from a snapping tendon, as discussed below. In addition to chronic inflammation as a source of pain, tears in the abductor tendons and musculature can also result and contribute to pain generation, analogous to rotator cuff tears in the shoulder. The gluteus medius, which inserts on the lateral and posterior facets of the greater trochanter, is most commonly torn along its articular side, and akin to the shoulder, insertional medius tears can be partial (most often), intrasubstance, or complete [63]. GTPS can be effectively treated with arthroscopic bursectomy, iliotibial band release, and/or tendon repair to the greater trochanter depending on the offending anatomy [64]. Articular surface partial-thickness tears can be difficult or impossible to visualize from the peritrochanteric space; thus, recently trans-tendinous repair of these lesions has been advocated [63].

Snapping hip syndrome is characterized by an audible (internal coxa saltans) or visible (external coxa saltans) snapping of the hip when the joint is in motion and may be accompanied by pain. Sources of the snapping can include loose bodies in the joint and extra-articular causes including a thickened iliotibial band or gluteus maximus (external coxa saltans) which may snap over the greater trochanter when the hip is flexed and then extended. A snapping hip may also be the result of the iliopsoas tendon (internal coxa saltans) displacing over the iliopectineal eminence, anterior inferior iliac spine (AIIS), acetabular rim, or femoral head. Friction from repetitive snapping leads to chronic inflammation and potential tears of the offending tendon. Asymptomatic snapping requires no treatment; however, arthroscopic procedures for recalcitrant symptoms are effective at addressing pain from a snapping tendon [65, 66]. Techniques include the removal of osseous impingements and/or the release or lengthening of the iliopsoas or iliotibial band to alleviate symptoms [67]. Care should be taken in patients with increased acetabular or femoral retroversion, however, as the psoas tendon may act as a dynamic stabilizer of the hip and lengthening procedures may lead to functional weakness and pain [18].

Avulsion of the hamstring off the ischial tuberosity is a rare injury that occurs during forceful hip flexion and knee extension [68]. Waterskiing accidents are the most common cause of proximal hamstring avulsions. Reattachment of two or three tendon avulsion injuries with significant retraction is often performed in young and active patients with favorable outcomes and a high rate of return to sport [69, 70]. As the use of extra-articular arthroscopy about the hip continues to expand, the role of endoscopic repair of proximal hamstring tendon avulsions is currently being explored [71]. Arthroscopic approach to these injuries should be restricted to only those arthroscopists with adept skills and thorough anatomic knowledge of the deep gluteal space. There are currently no studies that have defined the outcomes and complications associated with arthroscopic repair and whether this technique offers any benefit over traditional open techniques. The presence of the sciatic nerve and gluteal vasculature in the deep gluteal space mandate that care be taken to visualize and protect these vital structures during this procedure. Currently, this application may be more predictably used for treatment of recalcitrant proximal hamstring tendinopathy with high-grade tears. Areas of tendinosis can be debrided, and creation of a bleeding bony bed at the ischial tuberosity aids with tendon repair. Chronic ruptures, which may require reconstruction with allograft material, are currently best treated via an open surgical approach [72].

The sciatic nerve passes through the sciatic notch intimately in association with the piriformis muscle, and injury to this muscle, which results in spasm or contracture, may compress the nerve and lead to symptoms [73]. Approximately 17 % of patients may have variations in the course of the sciatic nerve in relation to the piriformis that must be considered [74]. The sciatic nerve may exit through the piriformis (0.5 %), a portion of the nerve may exit through the piriformis (13.7 %), or it may be double branched with the piriformis sandwiched between the nerve branches (1.3 %). Pain can also be secondary to nerve entrapment or compression by the hamstring origin and quadratus femoris/gemellus inferior and obturator internus/gemellus superior muscles or scar tissue, commonly described as fibrous bands [75]. Nerve entrapment is aggravated by hip flexion and internal or external rotation and can cause pain over the buttocks that can radiate down the dorsal thigh. The nerve normally accommodates hip movement, but nearby inflamed or contracted muscle reduces the space available for nerve excursion.

Endoscopic treatment has been used to reduce pain associated with sciatic nerve compression by addressing each offending structure; however, this treatment can be ineffective if tethering structures are too proximal in the pelvis or distal in the thigh [75]. Endoscopic decompression of the sciatic nerve requires accurate knowledge of the periarticular space and precise surgical technique to ensure all potential offending structures are addressed. Sciatic nerve decompression is a relatively new indication for hip endoscopy, and as such it is advisable that this approach be performed with great caution and only by surgeons familiar with the anatomy of the subgluteal space.