Hip osteoarthritis: what the radiologist wants to know

The impact of mobilization on hip osteoarthritis

BACKGROUND

Osteoarthritis is one of the most common joint disorders. It causes pain, stiffness and a decreased range of motion which have a significant impact on daily activities and gait, consequently leading to disability.

OBJECTIVE

The aim of this study is to compare hip mobilization with non-weight bearing exercises.

METHODS

A total of 57 females aged between 55-65 were divided into 2 groups. In the control group non-weight bearing exercises were conducted, whereas the research group received hip mobilization.

RESULTS

The Lequesne index significantly improved in the research group as compared with the control group. Hip function improved both in the control and research groups. Active hip extension increased by 0.54, while active abduction rose by 2.14 after non-weight bearing exercises. In the control group after mobilization both passive and active hip extension increased significantly by 3.53, active abduction by 5 and passive by 4.41, while active and passive internal rotation by 3.82 and 4.56, respectively. In both groups pain decreased.

CONCLUSIONS

Mobilization increases hip range of motion, decreases pain and improves hip function more than non-weight bearing exercises.

Unrecognized Chondrosarcoma as a Cause of Total Hip Arthroplasty Failure

Background

Total hip arthroplasty (THA) is one of the most successful procedures in orthopedic surgery. The most frequent THA indications are osteoarthritis and avascular necrosis, whereas symptomatic aseptic loosening is the most common indication to revision surgery. Chondrosarcoma (CS) is the most frequent bone sarcoma in adults, and proximal femur is the most prevalent location. Wide resection is the treatment of choice.We report 3 cases of unrecognized high-grade CS in the setting of primary or revision THA and reviewed the literature on this rare clinical presentation.

Methods

A systematic literature review on CS in the setting of THA, published between 1980 and 2020, was performed on PubMed, Embase, Medline, Ovid SP, and Web of Science, using the guidelines set in the Preferred Reporting Items for Systematic Reviews and Mata-analyses (PRISMA).

Results

Case series: Three patients were referred to our sarcoma center after failure of THA due to unrecognized high-grade CS. All 3 had rapid fatal outcome. Literature review: Fifty-nine articles were identified, of which 8 were included in the study. They confirmed that primary or revision THA failure due to unrecognized CS is extremely rare, with only few cases reported in the literature.

Conclusions

Before proceeding to primary or revision arthroplasty, diagnosis must be ascertained. Atypical presentation of a common pathology, such as osteoarthritis, avascular necrosis, or aseptic loosening of an endoprosthesis, should raise suspicion for another cause to symptoms, and additional workup be performed. As our cases demonstrated, unrecognized or inadequately managed bone sarcoma may lead to poor or even fatal outcome.

Does This Patient Have Hip Osteoarthritis?: The Rational Clinical Examination Systematic Review

IMPORTANCE

Hip osteoarthritis (OA) is a common cause of pain and disability.

OBJECTIVE

To identify the clinical findings that are most strongly associated with hip OA.

DATA SOURCES

Systematic search of MEDLINE, PubMed, EMBASE, and CINAHL from inception until November 2019.

STUDY SELECTION

Included studies (1) quantified the accuracy of clinical findings (history, physical examination, or simple tests) and (2) used plain radiographs as the reference standard for diagnosing hip OA.

DATA EXTRACTION AND SYNTHESIS

Studies were assigned levels of evidence using the Rational Clinical Examination scale and assessed for risk of bias using the Quality Assessment of Diagnostic Accuracy Studies tool. Data were extracted using individual hips as the unit of analysis and only pooled when findings were reported in 3 or more studies.

MAIN OUTCOMES AND MEASURES

Sensitivity, specificity, and likelihood ratios (LRs).

RESULTS

Six studies were included, with data from 1110 patients and 1324 hips, of which 509 (38%) showed radiographic evidence of OA. Among patients presenting to primary care physicians with hip or groin pain, the affected hip showed radiographic evidence of OA in 34% of cases. A family history of OA, personal history of knee OA, or pain on climbing stairs or walking up slopes all had LRs of 2.1 (sensitivity range, 33%-68%; specificity range, 68%-84%; broadest LR range: 95% CI, 1.1-3.8). To identify patients most likely to have OA, the most useful findings were squat causing posterior pain (sensitivity, 24%; specificity, 96%; LR, 6.1 [95% CI, 1.3-29]), groin pain on passive abduction or adduction (sensitivity, 33%; specificity, 94%; LR, 5.7 [95% CI, 1.6-20]), abductor weakness (sensitivity, 44%; specificity, 90%; LR, 4.5 [95% CI, 2.4-8.4]), and decreased passive hip adduction (sensitivity, 80%; specificity, 81%; LR, 4.2 [95% CI, 3.0-6.0]) or internal rotation (sensitivity, 66%; specificity, 79%; LR, 3.2 [95% CI, 1.7-6.0]) as measured by a goniometer or compared with the contralateral leg. The presence of normal passive hip adduction was most useful for suggesting the absence of OA (negative LR, 0.25 [95% CI, 0.11-0.54]).

CONCLUSIONS AND RELEVANCE

Simple tests of hip motion and observing for pain during that motion were helpful in distinguishing patients most likely to have OA on plain radiography from those who will not. A combination of findings efficiently detects those most likely to have severe hip OA.

Bone marrow edema in non-traumatic hip: high accuracy of dual-energy CT with water-hydroxyapatite decomposition imaging

OBJECTIVES

To evaluate the diagnostic performance of dual-energy CT with water-hydroxyapatite (HAP) imaging for bone marrow edema in patients with non-traumatic hip pain.

METHODS

Forty patients (mean age, 58 years; 16 male and 24 female) who underwent rapid kVp-switching dual-energy CT and MRI within 1 month between April 2018 and February 2019 with hip pain but no trauma were enrolled. Two radiologists retrospectively evaluated 80 hip joints for the presence, extent (femoral head involved, head and neck, and head to intertrochanter), and severity (mild edema, moderate, severe) of bone marrow edema on dual-energy water-HAP images. Water mass density (mg/cm³) on water-HAP images was determined with region of interest-based quantitative analysis. MRI served as the standard of reference.

RESULTS

Sensitivity, specificity, and accuracy of readers 1 and 2 for the identification of bone marrow edema in water-HAP images were 85% and 85%, 93% and 73%, and 89% and 79%, respectively. The area under the receiver operating characteristic curve was 0.96 for reader 1 and 0.91 for reader 2 for differentiation of the presence of edema from no edema. The optimal water mass density to classify the presence of edema for reader 1 was 951 mg/cm³ with 93% sensitivity and 93% specificity and for reader 2 was 957 mg/cm³ with 80% sensitivity and 80% specificity. The more severe the edema, the higher was the mean water density value (p < 0.035).

CONCLUSION

Dual-energy water-HAP images showed good diagnostic performance for bone marrow edema in patients with non-traumatic hip pain.

KEY POINTS

• Dual-energy water-HAP imaging depicts bone marrow edema in patients with non-traumatic hip pain and may serve as an alternative to MRI in select patients. • A cutoff value of 951 mg/cm³mean water mass density results in 93% sensitivity and 93% specificity for the detection of bone marrow edema. • The more severe the bone marrow edema, the higher the mean water density value.

INFLUENCE OF AGE ON PARAMETERS FOR FEMOROACETABULAR IMPINGEMENT AND HIP DYSPLASIA IN X-RAYS

Objective:

While several radiographic parameters have been established to describe the geometry and pathology of the hip, their reference values and clinical significance remain a matter of dispute. The present study tests the hypothesis that age has a relevant impact on radiographic hip parameters.

Method:

Pelvic antero-posterior views were measured for CE angle, Sharp’s angle, acetabular depth-to-width ratio, femoral head extrusion index, roof obliquity, caput-collum-diaphyseal (CCD) angle, and Murray’s femoral head ratio, and the values obtained were correlated with age.

Results:

Significant weak and moderate linear correlations (all Ps<0.001) were observed between age and CE angle (ρ=0.31), Sharp’s angle (ρ=-0.38), extrusion index (ρ=-0.22), CCD angle (ρ=-0.15), depth-to-width ratio (ρ=-0.38), and roof obliquity (ρ=-0.19), while Murray’s femoral head ratio (ρ=0.05; P=0.274) was not associated with age. Interestingly, the parameters describing the acetabulum all showed a relevant increase in coverage with age, leading to CE-angles well beyond 40° and a Sharp’s angle below 35° in a large portion of asymptomatic older adults.

Conclusion:

While a decrease in CCD angle with age is described in most orthopedic textbooks, the changes observed with age in acetabular geometry far exceed those measured at the femoral head-neck junction. We recommend considering these alterations that may be attributable to age when formulating a radiographic diagnosis. Level of Evidence III, Diagnostic Studies - Investigating a Diagnostic Test.

Subchondral bone turnover, but not bone volume, is increased in early stage osteoarthritic lesions in the human hip joint

OBJECTIVE

The pathogenesis of osteoarthritis (OA) is not fully understood, but bone changes are suggested to be important. Bone turnover and bone volume (BV) in human hip OA were investigated in relation to the overlying cartilage degeneration using design-based stereological estimators.

MATERIALS AND METHODS

Femoral heads were obtained from 25 end-stage OA patients and 24 controls (CTL). Design-based stereological methods were used for sampling and quantification to obtain absolute estimates of volume and surface in the central trabecular and the subarticular bone region. The subarticular bone was further subdivided into regions according to the OARSI-score of the overlying articular cartilage in which erosion and osteoid surfaces were estimated.

RESULTS

In the subarticular region, bone volume (BV/TV) was 15.0% higher in OA patients compared to CTL; The fraction of erosive (ES/BS) and osteoid surfaces (OS/BS) were 56.2% and 72.8% higher in OA compared to CTL. In subarticular regions with none to mild cartilage degeneration (OARSI grade 0-2), ES/BS and OS/BS were 48.6% and 59.9% higher in OA compared to CTL, whereas BV/TV did not differ between OA and CTL.

CONCLUSION

In human end-stage hip OA, BV and bone turnover correlate with the degree of local cartilage degeneration. Subarticular bone sclerosis was only present in regions corresponding to end-stage OA. However, in regions with only none to mild cartilage degeneration the underlying bone had significantly higher turnover in OA patients compared to the control group, suggesting that high bone turnover may contribute to the early pathogenesis of OA.

Patient satisfaction after arthroscopic repair of acetabular labral tears

Background

Acetabular labral tear is a main cause of hip pain and disability, often requiring surgical treatment. Improvements of hip arthroscopic technique have produced positive outcomes after labral repair with arthroscopy. The purpose of this study was to determine clinical outcomes and patient satisfaction after arthroscopic repair of acetabular labral tear.

Methods

We interviewed 21 patients (10 men and 11 women; mean age, 36 years [range, 22 to 57 years]) with acetabular labral tears that had been repaired arthroscopically in terms of satisfaction of the procedure. In addition, clinical outcome was assessed using visual analog scale (VAS) score, University of California, Los Angeles (UCLA) activity, Western Ontario and McMaster Universities (WOMAC) osteoarthritis index, and Harris hip score, and radiologic outcome was assessed using serial radiography. The patients were followed for 24-50 months.

Results

The mean Harris hip score was 73 points (range, 64 to 84 points) preoperatively and 83 points (range, 66 to 95 points) postoperatively. Fifteen hips (71%) were rated excellent and good. The mean WOMAC osteoarthritis index and VAS scores were improved at final follow-up. UCLA activity at the latest follow-up improved in 16 patients. The Tonnis grade of osteoarthritis at the latest follow-up did not change in all patients. Eighteen of the patients (86%) were satisfied with the procedure.

Conclusions

High rate of satisfaction after arthroscopic repair of acetabular labral tears is an encouraging outcome. Arthroscopic treatment of labral tears might be a useful technique in patients with hip pathologies, such as femoroacetabular impingement with labral tears.

Correlation of Structural Bony Abnormalities and Mechanical Symptoms of Hip Joints

PURPOSE

The purpose of this study is to determine structural bony abnormalities predisposing for femoroacetabular impingement by comparison of patients with and without mechanical symptoms.

MATERIALS AND METHODS

We conducted this comparative study on 151 patients (151 hips; mean age 44.8 years; range 16-73 years) with mechanical symptoms with results of multi-detector computed tomography (MDCT) arthrography (the symptomatic group). Each patient was matched with a control who underwent MDCT due to ureter stone (the asymptomatic group) in terms of age, gender, site (right or left), and time at diagnosis. Acetabular evaluations, which included cranial and central anteversion and anterior and lateral center edge angles and femoral measurements, were performed. In addition, we evaluated the prevalence and characteristics of structural bone abnormalities between the two groups.

RESULTS

The prevalence for patients who had at least one structural bony abnormality in the symptomatic and asymptomatic groups was 80.1% (121/151) and 54.3% (82/151), respectively (odds ratio: 3.39, 95% confidence interval: 2.30-5.66; P<0.001). The most common osseous abnormality was the isolated Pincer type in both groups: 89 (73.6%) of 121 hips with an osseous abnormality in the symptomatic group and 57 (69.5%) of 82 hips with an osseous abnormality in the asymptomatic group. By analysis of CT arthrography in symptomatic patients, a labral tear was found in 107 hips (70.9%), and 86 (80%) of these hips had a structural bony abnormality.

CONCLUSION

A significantly greater prevalence rate of structural bony abnormality was observed for the symptomatic group than for the asymptomatic group. These findings are helpful for development of appropriate treatment plans.

Herniation pits as a radiographic indicator of pincer-type femoroacetabular impingement in symptomatic patients

PURPOSE

The role of herniation pits as a radiographic indicator is still debated. This case-control study was to determine (1) the prevalence and sizes of herniation pits and (2) the relationship between herniation pits and femoral and acetabular bony morphology consistent with femoroacetabular impingement.

METHODS

This comparative study was performed on 151 patients (151 hips; median patient age 46 years; range 16-73 years) with mechanical symptoms, who underwent multi-detector computed tomography (MDCT) arthrography (the symptomatic group), and an age-, gender-, site (left or right)-, and time (at diagnosis)-matched group of control patients that underwent multi-detector computed tomography due to an ureter stone (the asymptomatic group). Two orthopaedic surgeons reviewed images to evaluate the prevalence, sizes of herniation pits, and relationship with morphological abnormality.

RESULTS

The prevalences of herniation pits in symptomatic and asymptomatic groups were 23.8 % (36/151) and 3.3 % (5/151), respectively (OR 9.14, 95 % CI 3.47-24.30; p < 0.001). Herniation pits were found to be significantly associated with pincer-type abnormality (p = 0.034), especially central acetabular retroversion (p < 0.001).

CONCLUSIONS

This study shows that the prevalence of herniation pits is higher in symptomatic patients with femoroacetabular impingement, and herniation pits are associated with central acetabular retroversion. Furthermore, herniation pits were also found to be a useful predictor of pincer-type femoroacetabular impingement.

Radiological aspects of osteoarthritis

Osteoarthritis (OA) is one of the most frequent indications in musculoskeletal imaging because OA is the most prevalent musculoskeletal disease in developed countries. As the population becomes older and older, the need for adequate imaging techniques also increases. The various forms of osteoarthritis are associated with a high degree of illness-induced physical disability and reduced life quality. In some forms, the pathogenesis is complex and can require the discrimination of a variety of predisposing diseases. The specific forms of osteoarthritis will be highlighted in this article. In addition, the value of each imaging modality will be assessed, with special regard to the most common sites: hand, hip, and knee.

[Coxarthrosis - a radiological approach and guidelines]

CLINICAL/METHODICAL ISSUE

Coxarthrosis is one of the most frequent indications in radiological practice with a prevalence as high as 8%.

STANDARD RADIOLOGICAL METHODS

Radiography, sonography, computed tomography, magnetic resonance imaging.

METHODICAL INNOVATIONS

Magnetic resonance arthrography for detection of early stages of labral and chondral pathologies as well as detection of osteonecrosis at an early stage.

PERFORMANCE

Czerny C, Hofmann S, Neuhold A et al. (1996) Lesions of the acetabular labrum: accuracy of MR imaging and MR arthrography in detection and staging. Radiology 200(1):225-230. Czerny C, Oschatz E, Neuhold A et al. (2002) [MR arthrography of the hip joint]. Radiologe 42(6):451-456. Kramer J, Breitenseher M, Imhof H et al. (2000) [Diagnostic imaging in femur head necrosis]. Orthopade 29(5):380-388.

ACHIEVEMENTS

Is already established in clinical practice.

PRACTICAL RECOMMENDATIONS

Each modality has relevant indications.

Magnetic resonance imaging of subchondral bone marrow lesions in association with osteoarthritis

OBJECTIVES

This nonsystematic literature review provides an overview of magnetic resonance imaging (MRI) of subchondral bone marrow lesions (BMLs) in association with osteoarthritis (OA), with particular attention to the selection of MRI sequences and semiquantitative scoring systems, characteristic morphology, and differential diagnosis. Histologic basis, natural history, and clinical significance are also briefly discussed.

METHODS

PubMed was searched for articles published up to 2011, using the keywords bone marrow lesion, osteoarthritis, magnetic resonance imaging, bone marrow edema, histology, pain, and subchondral.

RESULTS

BMLs in association with OA correspond to fibrosis, necrosis, edema, and bleeding of fatty marrow as well as abnormal trabeculae on histopathology. Lesions may fluctuate in size within a short time and are associated with the progression of articular cartilage loss and fluctuation of pain in knee OA. The characteristic subchondral edema-like signal intensity of BMLs should be assessed using T2-weighted, proton density-weighted, intermediate-weighted fat-suppressed fast spin echo or short tau inversion recovery. Several semiquantitative scoring systems are available to characterize and grade the severity of BMLs. Quantitative approaches have also been introduced. Differential diagnoses of degenerative BMLs include a variety of traumatic or nontraumatic pathologies that may appear similar to OA-related BMLs on MRI.

CONCLUSIONS

Subchondral BMLs are a common imaging feature of OA with clinical significance and typical signal alteration patterns, which can be assessed and graded by semiquantitative scoring systems using sensitive MRI sequences.

Micro-CT quantification of subchondral endplate changes in intervertebral disc degeneration

BACKGROUND

The intervertebral disc (IVD) is dependent on nutrient provision through a cartilage layer with underlying subchondral bone, analogous to joint cartilage. In the joint, subchondral bone remodeling has been associated with osteoarthritis (OA) progression due to compromised nutrient and gas diffusion and reduced structural support of the overlaying cartilage. However, subchondral bone changes in IVD degeneration have never been quantified before.

OBJECTIVE

The aim of this study is to determine the subchondral bone changes at different stages of IVD degeneration by micro-CT.

METHODS

Twenty-seven IVDs including the adjacent vertebral endplates were obtained at autopsy. Midsagittal slices, graded according the Thompson score, were scanned. Per scan 12 standardized cylindrical volumes of interest (VOI) were selected. Six VOIs contained the bony endplate and trabeculae (endplate VOIs) and six accompanying VOIs only contained trabecular bone (vertebral VOIs). Bone volume as percentage of the total volume (BV/TV) of the VOI, trabecular thickness (TrTh) and connectivity density (CD) were determined.

RESULTS

An increase in BV/TV and TrTh was found in endplate VOIs of IVDs with higher Thompson score whereas these values remained stable or decreased in the vertebral VOIs.

CONCLUSION

The increase in bone volume combined with the increase in TrTh in endplate VOIs strongly suggest that the subchondral endplate condenses to a more dense structure in degenerated IVDs. This may negatively influence the diffusion and nutrition of the IVD. The endplate differences between intact and mild degenerative IVDs (grade II) indicate an early association of subchondral endplate changes with IVD degeneration.

Prediction of femoral fracture load: cross-sectional study of texture analysis and geometric measurements on plain radiographs versus bone mineral density

PURPOSE

To use standard radiographs to determine which combination of co-occurrence textural parameters, geometric measurements, and cortical thickness measurements from femur radiographs provided the best estimate of femoral failure load and to compare these with total hip dual-energy x-ray absorptiometry bone mineral density (BMD) evaluation.

MATERIALS AND METHODS

Digital radiographs of 40 pairs of excised femurs (24 women, 16 men; mean age, 82 years + or - 12 [standard deviation]) were obtained. Regions of interest in the femoral neck, greater trochanter, intertrochanteric area, and femoral head were then selected. Three textural parameters derived from a co-occurrence matrix were estimated with imaging software. Neck-shaft angle, femoral neck axis length, calcar femorale thickness, and internal and external femoral shaft thickness were assessed. The femurs were randomly allocated to single-stance (femoral neck fracture) or side-impact (intertrochanteric fracture) configurations for failure load measurement.

RESULTS

Textural parameters correlated significantly with site-matched BMD. Stepwise regression analysis was performed, and total hip BMD explained 73% and 78% of the failure load in single-stance and side-impact configurations, respectively. Combining internal femoral shaft thickness with one or two textural parameters explained 72%-79% of failure load variance in the single-stance configuration and 63%-76% of failure load variance in the side-impact configuration.

CONCLUSION

In these excised femurs, combining textural parameters with cortical thickness measurements had a performance comparable to that of BMD alone in the explanation of femoral failure load.

Hip arthroscopy: state of the art

INTRODUCTION

The unique anatomy of the hip is challenging, and has slowed the progress of hip arthroscopy. The aim of this review is to provide an updated synthesis of existing clinical evidence on hip arthroscopy.

SOURCES OF DATA

A systematic computerized literature search was conducted by two independent reviewers using an iterative manipulation process of the keywords used singularly or in combination. The following databases were accessed on 30th November, 2009: PubMed (http://www.ncbi.nlm.nih.gov/sites/entrez/); Ovid (http://www.ovid.com); and Cochrane Reviews (http://www.cochrane.org/reviews/). Case reports, literature reviews, letters to editors and articles not including outcome measures were excluded. Twenty-three publications met the inclusion criteria and were included.

AREAS OF AGREEMENT

Hip arthroscopy can provide an alternative to traditional arthrotomy with great therapeutic potential. However, the available data do not allow definitive conclusion on its routine use.

AREAS OF CONTROVERSY

It is still unclear whether arthroscopy is superior to open surgery in the management of femoroacetabular impingement and labral lesions.

GROWING POINTS

Rather than providing strong evidence for or against the use of hip arthroscopy, this study generates potential areas for additional prospective investigations to evaluate the role of hip arthroscopy in clinical practice.

AREAS TIMELY FOR DEVELOPING RESEARCH

There is a need to perform appropriately planned and powered studies to clarify the role of arthroscopy in hip pathology.

[Coxarthrosis--an update]

Degenerative osteoarthritis of the hip joint (coxarthrosis) is the most common disease of the hip joint in adults. The diagnosis is based on a combination of radiographic findings and characteristic clinical symptoms. The lack of a radiographic consensus definition has seemingly resulted in a variation of the published incidences and prevalence of degenerative osteoarthritis of the hip joint. The chronological sequence of degeneration includes the following basic symptoms on conventional radiographs and CT: joint space narrowing, development of osteophytes, subchondral demineralisation/sclerosis and cyst formation, as well as loose bodies, joint malalignment and deformity. MR imaging allows additional visualization of early symptoms and/or activity signs such as cartilage edema, cartilage tears and defects, subchondral bone marrow edema, synovial edema and thickening, joint effusion and muscle atrophy.The scientific dispute concerns the significance of (minimal) joint malalignment (e.g. impingement, dysplasia etc.) and forms of malpositioning which as possible prearthrosis have a high probability of leading to degenerative osteoarthritis. Moreover, without any question, the preservation of joint containment and gender differences are important additional basic diagnostic principles, which have gained great interest in recent years.In research different MR procedures such as Na and H spectroscopy, T2*-mapping etc. with ultrahigh field MR allow cartilage metabolism and its changes in early degenerative osteoarthritis ("biochemical imaging") to be studied. There is no doubt that even in a few years new profound knowledge is to be expected in this field.

MRI in degenerative arthritides: structural and clinical aspects

Owing to the potential to image not only bone but also cartilage, bone marrow, and the surrounding internal soft tissue structures, MRI is particularly useful for the assessment of degenerative arthritides. Cartilage-sensitive MRI techniques have been shown to have a significant correlation with arthroscopic grading scores. MRI is also helpful in differentiating osteoarthritis from avascular necrosis, labral pathology, and pigmented villonodular synovitis. This chapter describes advanced imaging techniques, including driven equilibrium Fourier transform (DEFT) and steady-state free precision (SSFP) imaging, direct MRI arthrography, and 3D-T1rho-relaxation mapping.

Detection of calcium phosphate crystals in the joint fluid of patients with osteoarthritis - analytical approaches and challenges

Clinically, osteoarthritis (OA) is characterised by joint pain, stiffness after immobility, limitation of movement and, in many cases, the presence of basic calcium phosphate (BCP) crystals in the joint fluid. The detection of BCP crystals in the synovial fluid of patients with OA is fraught with challenges due to the submicroscopic size of BCP, the complex nature of the matrix in which they are found and the fact that other crystals can co-exist with them in cases of mixed pathology. Routine analysis of joint crystals still relies almost exclusively on the use of optical microscopy, which has limited applicability for BCP crystal identification due to limited resolution and the inherent subjectivity of the technique. The purpose of this Critical Review is to present an overview of some of the main analytical tools employed in the detection of BCP to date and the potential of emerging technologies such as atomic force microscopy (AFM) and Raman microspectroscopy for this purpose.