Acetabular labral tears are a mechanical cause of hip pain. Hip MR imaging should be performed on 3T magnets using small field of view and high-resolution imaging. If using a lower strength magnet, direct arthrography should be performed. The following should be used in the assessment for labral tear abnormalities on MR (or MR arthrography): labral morphology, abnormal T2 signal (or contrast) extension into the labral substance or chondrolabral junction. Description of the labral tear and extent of tear is useful for the hip preservation surgeon. Understanding the pitfalls around the acetabular labral complex will help avoid misinterpretation of labral tears.

Paralabral cysts in the acetabulum often occur in the setting of labral tears. While labral tears are commonly identified in femoroacetabular impingement syndrome, developmental dysplasia of the hip is also a cause of chondrolabral pathology. Our understanding of paralabral cysts has encouraged addressing the concomitant labral pathology, as this has been shown to result in cyst resolution. However, recent evidence suggests in the setting of hip dysplasia, addressing the bony pathology of the acetabulum with an isolated acetabular reorientation osteotomy allows for cyst resolution and significant improvement in clinical outcomes despite persistent labral tears postoperatively. While further investigation is needed to delineate the effects of persistent labral tears after isolated periacetabular osteotomy, addressing the acetabular undercoverage remains critical in the treatment of these patients.

To investigate whether paralabral cysts identified incidentally on preoperative magnetic resonance imaging/arthrography predict 2-year functional outcomes after arthroscopic acetabular labral repair.

Prospectively collected data for patients undergoing primary hip arthroscopy by a single surgeon from 2014 to 2020 were retrospectively reviewed. Included patients were ≥18 years and completed baseline patient-reported outcome measures (PROMs) with additional follow-up at 3, 6, 12, and 24 months. Exclusion criteria were labral debridement, hip dysplasia, advanced hip osteoarthritis (Tönnis > 1), or previous ipsilateral hip surgery. Patients were stratified based on the presence of paralabral cysts identified on magnetic resonance imaging/arthrography. Primary outcomes were International Hip Outcome Tool and modified Harris Hip Score. Secondary outcomes included other PROMs and the visual analog pain scale. Outcomes were compared between cohorts using linear mixed-effects models and Fisher's exact tests. Sensitivity analyses accounted for preoperative PROMs, nonlinear improvement trajectories, and relevant baseline characteristics.

Of the 182 included hips (47.8% female; mean ± standard deviation age, 36.9 ± 11.4), 30 (16.4%) had paralabral cysts. During the 2-year study period, there were no significant differences between patients with and without paralabral cysts in terms of International Hip Outcome Tool scores (weighted difference = 1.60; 95% confidence interval [CI], -5.09, 8.28; P = .64), modified Harris Hip Scores (weighted difference = 0.56; 95% CI, -4.16, 5.28; P = .82), or any secondary outcomes (except for HOS-Sports Subscale at 3 months [mean difference = -11.85; 95% CI, -22.85, -0.84; P = .035]). Furthermore, there were no significant differences in clinically meaningful outcomes (P > .05 for all), revision rates (P > .99), or conversion to total hip arthroplasty between cohorts (P > .99). These results held across all sensitivity analyses.

Although preoperative paralabral cysts were associated with worse cam impingement and more severe chondral damage observed intraoperatively, they did not predict 2-year functional outcomes or clinically meaningful improvements, suggesting that incidentally discovered paralabral cysts are not a contraindication for arthroscopic labral repair.

Level III, retrospective cohort study.

The hip is a uniquely constrained joint with critical static stability provided by the labrum, capsule and capsular ligaments, and ligamentum teres. The labrum is a fibrocartilaginous structure along the acetabular rim that encircles most of the femoral head. Labral tears are localized based on the clock-face method, which determines the extent of the tear while providing consistent terminology for reporting. Normal labral variants can mimic labral disease and can be differentiated by assessment of thickness or width, shape, borders, location, and associated abnormalities. The Lage and Czerny classification systems are currently the most well-known arthroscopic and imaging systems, respectively. Femoroacetabular impingement is a risk factor for development of labral tears and is classified according to bone dysmorphisms of the femur ("cam") or acetabulum ("pincer") or combinations of both (mixed). The capsule consists of longitudinal fibers reinforced by ligaments (iliofemoral, pubofemoral, ischiofemoral) and circular fibers. Capsular injuries occur secondary to hip dislocation or iatrogenically after capsulotomy. Capsular repair improves hip stability at the expense of capsular overtightening and inadvertent chondral injury. The ligamentum teres is situated between the acetabular notch and the fovea of the femoral head. Initially considered to be inconsequential, recent studies have recognized its role in hip rotational stability. Existing classification systems of ligamentum teres tears account for injury mechanism, arthroscopic findings, and treatment options. Injuries to the labrum, capsule, and ligamentum teres are implicated in symptoms of hip instability. The authors discuss the labrum, capsule, and ligamentum teres, highlighting their anatomy, pathologic conditions, MRI features, and postoperative appearance. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material.

This article reviews the literature and the authors' experiences regarding the performance of lower extremity fluoroscopically guided procedures from the hip to the toes. An overview of injections and aspirations, their indications, risks, and complications are provided, focusing on anesthetics, corticosteroids, and contrast agents. A variety of approaches to each joint and the associated pearls and pitfalls of each approach will be discussed.

This article discusses two rare cases of intra-labral pigmented villonodular synovitis (PVNS) of the hip. The hip joint represents the second most common location of pigmented villonodular synovitis, second to the knee [1]. The majority of hip PVNS cases either diffusely involve the synovium or are focal lesions within the joint. The lesions and synovium show foci of low signal intensity related to hemosiderin deposition, a finding that differentiates PVNS from other causes of synovial proliferation. Our case report presents two rare manifestations of PVNS lesions localized within the hip labrum. This presentation could easily be mistaken for a cyst by imaging modality. Despite the rarity of this condition, we highlight the importance of questioning the possibility of intra-labral PVNS, when patients have persistent hip pain not responding to therapy and atypical imaging findings. Highlighting this rare presentation is crucial for establishing the correct diagnosis, guiding treatment, and obtaining the best clinical outcome.

Large acetabular paralabral cysts can cause compression of the surrounding neurovascular structures leading to sensory and motor deficits. We present a 68-year-old man with obturator nerve denervation from a paralabral cyst secondary to a labral tear associated with femoroacetabular impingement syndrome. Resolution of symptoms and return to full activities were achieved at 3 months and maintained beyond 1 year through open cyst excision, obturator neurolysis, arthroscopic femoral osteoplasty, and labral repair in the same surgical setting. The patient had a successful clinical outcome, with pain and dysfunction resolution.

Large paralabral cysts may cause obturator nerve compression, which can be successfully treated with open nerve decompression and arthroscopic treatment of labral pathology.

To present cases of juxtaneural ganglia arising from the hip with a discussion of the magnetic resonance imaging (MRI) findings, presenting symptoms, and possible treatment option.

Two radiologists performed a consensus review of MRI scans obtained between January 2013 and March 2021 to identify patients with juxtaneural ganglia around the hip. A total of 11 patients with 11 juxtaneural ganglia were identified. Medical records and MRI findings were retrospectively reviewed.

Eight patients had lesions involving the sciatic nerve, and three patients had lesions involving the obturator nerve. Sciatic ganglia arose from a paralabral cyst in the posteroinferior quadrant and continued through a narrow channel running along the posterior acetabulum, showing increased diameter in the sciatic foramen and intrapelvic portion. Obturator ganglia showed a J- or reverse J-shape on the coronal imaging plane and extended from a paralabral cyst in the anteroinferior quadrant via the obturator canal. Nine patients (9/11, 81.8%) had symptoms resembling those of lumbosacral radiculopathy. Four patients underwent arthroscopic surgery, and one patient underwent ultrasound-guided aspiration, all of whom showed partial improvement. Spontaneous decrease in the extent of the ganglion was observed in three patients (3/11, 27.3%).

This article describes rare cases of juxtaneural ganglia arising from the hip joint and involving the sciatic and obturator nerves. The lesions share similar MRI findings, and each type of cyst (sciatic or obturator ganglia) involves a specific labral quadrant.

We report the case of an active 8-year-old patient with a 2-year history of groin and thigh pain. Magnetic resonance imaging of the hip demonstrated a paralabral cyst arising from a superior labral tear. Arthroscopic labral repair and decompression of the cyst were performed, and the patient remains asymptomatic at 2-year follow-up.

Acetabular labral tears with concomitant paralabral cysts have been described in the literature in the adult population and successfully treated arthroscopically. We propose that surgeons should be aware of this as a cause for undiagnosed groin and thigh pain in the pediatric population and that arthroscopic management is successful.

To evaluate the prevalence and location of paralabral cysts and the correlation between the type of femoroacetabular impingement (FAI) and acetabular labral tears, as well as the location of the paralabral cysts.

Patients who received a diagnosis of FAI syndrome using plain radiography, magnetic resonance imaging or magnetic resonance arthrography, or computed tomographic arthrography from 2010 to 2015 were included in this study. The exclusion criteria were patients with arthritis (Tönnis grade 2 or greater) or dysplasia. We identified paralabral cysts and their location, size, configuration. Correlations between the type of FAI and labral tears and paralabral cysts were analyzed using the χ-square test.

Among 506 patients with FAI, paralabral cysts were found in 51 patients (55 hips) and were located anterosuperiorly in 40% of cases, posterosuperiorly in 36%, anteroinferiorly in 17%, and posteroinferiorly in 8%. We identified multilocular cysts in 60% of hips and unilocular cysts in 40%. Labral tears were radiographically found in 44 of 55 hips with paralabral cysts (80%); they were located anterosuperiorly in 59% and posterosuperiorly in 41%. Although paralabral cysts were found in the anteroinferior and posteroinferior areas, acetabular labral tears were not identified in the anteroinferior and posteroinferior areas. Classification of the type of FAI showed cam type in 14 of 55 hips (25.5%), pincer type in 16 (29%), mixed type in 7 (13%), labral tears in 15 (27%), and normal findings in 3 (5.5%). No correlation was found between the type of FAI and labral tears (P = .739) or the location of paralabral cysts (P = .228).

Paralabral cysts in patients with FAI most commonly are found in the anterosuperior area and are of the multilocular type. Although paralabral cysts in the anterosuperior and posterosuperior portions are related to labral tears, those in the anteroinferior and posteroinferior portions are not.

Level IV, diagnostic case series.

Paralabral cysts are often associated with labral and other intraarticular hip pathology; MRI as well as diagnostic ultrasound can assist in diagnosis. Although often considered a coincidental finding, paralabral cysts can be a separate pain generator about the hip through compression of surrounding anatomy. They can also be initially mistaken for malignancy or other pathology by providers unfamiliar with their appearance. We present the case of an active 33-year-old female with right hip pain secondary to a large symptomatic posterior acetabular paralabral cyst with concomitant anterior labral tear. Following diagnosis on MRI, treatment included ultrasound-guided aspiration of the cyst, followed by arthroscopic anterior labral repair and separate cyst decompression from a posterior portal. The patient had complete resolution of her symptoms.

The natural history of femoroacetabular impingement (FAI) remains incompletely understood. In particular, there is limited documentation of joint damage in adolescent patients with limited range of motion (LROM) of the hip, which is commonly associated with FAI.

To evaluate changes in magnetic resonance imaging (MRI), radiographs, and clinical examinations over 5 years in a group of athletes from a wide variety of sports with asymptomatic LROM of the hip compared with matched controls.

Cohort study (prognosis); Level of evidence, 2.

The authors screened 226 male and female athletes aged 12 to 18 years presenting for preparticipation sports physical examinations. Using a goniometer, we identified 13 participants with at least one hip having internal rotation <10° with the hip flexed to 90°. Overall, 21 of 26 hips (81%) had internal rotation <10°. These participants were age- and sex-matched to 13 controls with internal rotation >10°. At the time of enrollment, all participants were asymptomatic and underwent a complete hip examination and radiographic imaging with radiographs (anteroposterior [AP] and von Rosen views) and non-arthrogram MRI. Participants returned at 5-year follow-up and underwent repeat hip examinations, imaging (AP and lateral radiographs and non-arthrogram MRI), and hip function questionnaires. MRI scans were classified as "normal" versus "abnormal" based on the presence of any of 13 scored chondral, labral, or osseous abnormalities. Comparisons between the LROM group and control group were performed using generalized linear models (either linear, logistic, or log-binomial regression as appropriate for the outcome) with generalized estimating equations to account for the within-participant correlation due to patients having both hips included. Relative risk (RR) estimates are reported with 95% CIs.

At the time of study enrollment, 16 of 26 hips (62%) in the LROM group had abnormal MRI findings within the acetabular labrum or cartilage compared with 8 of 26 hips (31%) in the control group (RR, 2.0; 95% CI, 0.95-4.2; P = .067). The mean alpha angle measured from radial MRI sequences was 58° in the LROM group versus 44° in the control group ( P < .0001). In the LROM group, 13 of 26 hips (50%) had a positive anterior impingement sign, whereas 0 of 26 hips (0%) had a positive anterior impingement sign in the control group. At 5-year follow-up, 18 of 19 hips (95%) in the LROM group had abnormal MRI findings compared with 14 of 26 hips (54%) in the control group (RR, 1.7; 95% CI, 1.1-2.7; P = .014). New or progressive findings were documented on MRI in 15 of 20 hips in the LROM group compared with 8 of 26 hips in the control group (RR, 2.4; 95% CI, 1.2-4.8; P = .011). Six of 22 hips (27%) in the LROM group progressed from Tönnis grade 0 to Tönnis grade 1 in degenerative changes, whereas all 26 hips in the control group remained at Tönnis grade 0 on hip radiographs. In the LROM group, 11 of 22 hips (50%) had a positive anterior impingement sign, whereas 1 of 26 hips (4%) had a positive anterior impingement sign in the control group. A cam deformity (alpha angle >55° on lateral radiographs) was present in 20 of 22 hips (91%) in the LROM group and 12 of 26 hips (46%) in the control group ( P = .0165). The following variables at baseline were associated with an increased risk of degenerative changes at 5-year follow-up for the entire cohort: decreased hip internal rotation, positive anterior impingement sign, decreased hip flexion, increased alpha angle, and presence of a cam lesion.

At 5 years, young athletes with LROM of the hip showed increased progressive degenerative changes on MRI and radiographs compared with matched controls. Although the majority of these participants remained asymptomatic, those with features of FAI had radiographic findings consistent with early osteoarthritis. These outcomes suggest that more aggressive screening and counseling of young active patients may be helpful to prevent hip osteoarthritis in those with FAI.

Magnetic resonance arthrogram (MRA) with radial cuts is presently the best available preoperative imaging study to evaluate chondrolabral lesions in the setting of femoroacetabular impingement (FAI). Existing followup studies for surgical treatment of FAI have evaluated predictors of treatment failure based on preoperative clinical examination, intraoperative findings, and conventional radiography. However, to our knowledge, no study has examined whether any preoperative findings on MRA images might be associated with failure of surgical treatment of FAI in the long term.

The purposes of this study were (1) to identify the preoperative MRA findings that are associated with conversion to THA, any progression of osteoarthritis, and/or a Harris hip score of < 80 points after acetabuloplasty and/or osteochondroplasty of the femoral head-neck junction through a surgical hip dislocation (SHD) for FAI at a minimum 10-year followup; and (2) identify the age of patients with symptomatic FAI when these secondary degenerative findings were detected on preoperative radial MRAs.

We retrospectively studied 121 patients (146 hips) who underwent acetabuloplasty and/or osteochondroplasty of the femoral head-neck junction through SHD for symptomatic anterior FAI between July 2001 and March 2003. We excluded 35 patients (37 hips) with secondary FAI after previous surgery and 11 patients (12 hips) with Legg-Calvé-Perthes disease. All patients underwent preoperative MRA to further specify chondrolabral lesions except in 19 patients (32 hips) including 17 patients (20 hips) who presented with an MRI from an external institution taken with a different protocol, 10 patients with no preoperative MRA because the patients had already been operated on the contralateral side with a similar appearance, and two patients (two hips) refused MRA because of claustrophobia. This resulted in 56 patients (65 hips) with idiopathic FAI and a preoperative MRA. Of those, three patients (three hips) did not have minimal 10-year followup (one patient died; two hips with followup between 5 and 6 years). The remaining patients were evaluated clinically and radiographically at a mean followup of 11 years (range, 10-13 years). Thirteen pathologic radiographic findings on the preoperative MRA were evaluated for an association with the following endpoints using Cox regression analysis: conversion to THA, radiographic evidence of any progression of osteoarthritis, and/or a Harris hip score of < 80. The age of the patient when each degenerative pattern was found on the preoperative MRA was recorded.

The following MRI findings were associated with one or more of our predefined failure endpoints: cartilage damage exceeding 60° of the circumference had a hazard ratio (HR) of 4.6 (95% confidence interval [CI], 3.6-5.6; p = 0.003) compared with a damage of less than 60°, presence of an acetabular rim cyst had a HR of 4.1 (95% CI, 3.1-5.2; p = 0.008) compared with hips without these cysts, and presence of a sabertooth osteophyte had a HR of 3.2 (95% CI, 2.3-4.2; p = 0.013) compared with hips without a sabertooth osteophyte. The degenerative pattern associated with the youngest patient age when detected on preoperative MRA was the sabertooth osteophyte (lower quartile 27 years) followed by cartilage damage exceeding 60° of the circumference (28 years) and the presence of an acetabular rim bone cyst (31 years).

Preoperative MRAs with radial cuts reveal important findings that may be associated with future failure of surgical treatment for FAI. Most of these factors are not visible on conventional radiographs or standard hip MRIs. Preoperative MRA evaluation is therefore strongly recommended on a routine basis for patients undergoing these procedures. Findings associated with conversion to arthroplasty, radiographic evidence of any progression of osteoarthritis, and/or a Harris hip score of < 80 points should be incorporated into the decision-making process in patients being evaluated for joint-preserving hip surgery.

Level III, therapeutic study.

Ganglion and synovial cysts occur mainly, but not necessarily, in association with osteoarthritis. Presentation varies widely, ranging from small, incidentally detected, asymptomatic lesions to giant ones that might be the source of symptoms, either due to their compressive effect on adjacent structures or due to complications, such as rupture. On magnetic resonance imaging they are typically presented as smooth, well-circumscribed, thin-walled, unilocular, and homogeneously T2-hyperintense lesions. An identifiable thin stalk communicating to the joint space is not infrequent. Nevertheless, depending on their age, anatomic location, and eventual complication, they might have many distinct appearances, including septae and internal debris, which the radiologist must be familiar with in order to accurately differentiate them from worrisome cystic-like lesions. With regard to this diversity, some illustrative cases are presented.

The objective of this article is to present the clinical use of aspiration and steroid injection under CT guidance for symptomatic paralabral cysts of the hip.

Four cases of symptomatic paralabral cysts of the hip were treated with aspiration and steroid injection after MR examinations had been performed. The imaging characteristics of the cysts, including the location, size, extracapsular extension, and associated labral tears, were evaluated. Under CT guidance, an 18-gauge spinal needle punctured the cyst, and aspiration was performed using local anesthesia. After irrigation with 50 % diluted iodine contrast material, steroid alone or a mixture of steroid and 1 % lidocaine was injected into the cyst. CT images during and after the procedure, procedural reports, and medical records were reviewed for analysis.

Three cysts were located in the anteroinferior region, while one cyst was located in the posterior region. At the 1-month follow-up, symptom improvement had been achieved in all four patients. However, in the patient who had the largest cyst with extracapsular extension, symptoms recurred after 5 months, and the patient underwent surgery.

CT-guided aspiration and steroid injection were feasible for the treatment of symptomatic paralabral cysts of the hip. During the procedures, all four cysts collapsed.

An acetabular paralabral cyst is a benign soft tissue cyst usually seen in association with a tear of the acetabular labrum. Acetabular paralabral cysts are often the cause of joint pain, but they rarely cause compression of the adjacent neurovascular structures. We present a case of a 63-year-old male patient who had paresis and atrophy of right hip adductor muscles. Right obturator neuropathy was confirmed through an electrodiagnostic study. In addition, magnetic resonance imaging showed a paralabral cyst in the right acetabulum which extended to the pelvic wall. The patient underwent conservative treatment without surgical procedure. The pain was decreased after 1 month of conservative therapy. The pain was decreased at the 1-month follow-up. Follow-up electromyography showed polyphasic motor unit potentials in adductor magnus and adductor longus muscles. Based on the experience of this case, an acetabular paralabral cyst should be considered as one of the rare causes of obturator neuropathy.

The femoroacetabular impingement (FAI) is an impingement characterized by repetitive abutment between the femur and the acetabular rim during hip motion due to loss of joint clearance (Imam and Khanduja in Int Orthop 35(10):1427-1435, 2011; James et al. in AJR Am J Roentgenol 187(6):1412-1419, 2006). Femoroacetabular impingement (FAI) can be classified as either cam or pincer type, and it can be differentiated on the basis of a predominance of either a femoral or an acetabular abnormality (Pfirrmann et al. in Radiology 244(2):626, 2007; Ganz et al. in Clin Orthop Relat Res 466(2):264-272, 2008). In cases of cam FAI, the nonspherical shape of the femoral head at the femoral head-neck junction and reduced depth of the femoral waist lead to abutment of the femoral head-neck junction against the acetabular rim. In cases of pincer FAI, acetabular overcoverage limits the range of motion and leads to a conflict between the acetabulum and the femur. The most important role of preoperative MR evaluation in patients affected by FAI is the accurate assessment of the damage's extension.

Acetabular labral tears or paralabral cysts in the hip are frequently detected using magnetic resonance imaging or arthrography. Unlike parameniscal cysts in the knee and paralabral cysts in the shoulder, reports of the outcomes of surgical treatment for paralabral cysts in the hip recalcitrant to conservative management are limited in the literature.The authors report 2 cases of paralabral cysts in the hip that were treated with arthroscopic surgery. The patients presented with chronic hip pain, and preoperative magnetic resonance imaging showed paralabral cysts at the superior aspect of the acetabulum. After failure of conservative management for more than 6 months, arthroscopic surgery was performed while the patients were under general anesthesia and in a supine position on a fracture table. Arthroscopic examination confirmed the preoperative diagnosis of paralabral cysts with degenerative labral fibrillation or tears in both patients. Arthroscopic cyst decompression and debridement of the degenerative labral tissues were performed using an arthroscopic thermal probe and a shaver.Clinical outcomes, determined by the Harris Hip Score, Western Ontario and McMaster Universities Osteoarthritis Index score, and University of California, Los Angeles activity score, were satisfactory for the 2 patients at 2 and 3 years postoperatively, respectively. Magnetic resonance imaging obtained for 1 patient at 6 months postoperatively showed complete decompression of the paralabral cyst. The authors believe that arthroscopic treatment for symptomatic hip paralabral cysts is a safe and effective procedure with excellent clinical outcomes.

Hip labral impingement can cause labral tears and secondary paralabral cyst formation. Femoroacetabular impingement is the main cause of labral impingement, but other conditions such as iliopsoas tendon impingement are described. There is no description of labral cyst resulting from psoas impingement treated arthroscopically in the literature. We present the case of a young sportsman with groin pain caused by psoas impingement with a labral tear and secondary paralabral cyst who was treated arthroscopically by cyst debridement, psoas tenotomy, and labral repair.