Whole-body MRI for the investigation of joint involvement in inflammatory arthritis.

OBJECTIVES: This study aimed to develop a novel whole-body MRI protocol capable of assessing inflammatory arthritis at an early stage in multiple joints in one examination. MATERIALS AND METHODS: Forty-six patients with inflammatory joint symptoms and 9 healthy volunteers underwent whole-body MR imaging on a 3.0 T MRI scanner in this prospective study. Image quality and pathology in each joint, bursae, entheses and tendons were scored by two of three radiologists and compared to clinical joint scores. Participants were divided into three groups based on diagnosis at 1-year follow-up (healthy volunteers, rheumatoid arthritis and all other types of arthritis). Radiology scores were compared between the three groups using a Kruskal-Wallis test. The clinical utility of radiology scoring was compared to clinical scoring using ROC analysis. RESULTS: A protocol capable of whole-body MR imaging of the joints with an image acquisition time under 20 min was developed with excellent image quality. Synovitis scores were significantly higher in patients who were diagnosed with rheumatoid arthritis at 12 months (p < 0.05). Radiology scoring of bursitis showed statistically significant differences between each of the three groups-healthy control, rheumatoid arthritis and non-rheumatoid arthritis (p < 0.05). There was no statistically significant difference in ROC analysis between MRI and clinical scores. CONCLUSION: This study has developed a whole-body MRI joint imaging protocol that is clinically feasible and shows good differentiation of joint pathology between healthy controls, patients with rheumatoid arthritis and patients with other forms of arthritis.

Determination of lower radiation dose limit for automatic measurement of adipose tissue.

The purpose of this study was to determine the lower limit of radiation dose required to measure visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) volumes when a fat quantification and noise reduction techniques (NRTs) are combined. For this purpose, we utilized CT colonography (CTC) images taken at low doses and manually segmented VAT and SAT fat volumes as ground truth. In order to derive the acceptable precision of the measurements needed to estimate the lower limit of radiation dose, we estimated the effect of different positioning during CT scanning on fat measurements using manually segmented VAT and SAT against normal dose. As a result, the acceptable accuracy of SAT and VAT was found to be 94.5% and 85.2%, respectively. Using these thresholds, the lower radiation dose limit required to accurately measure SAT using 5.25-mm slice-thick images was 1.5 mGy of size-specific dose estimates (SSDE), while the lower radiation dose limit required to accurately measure VAT was 0.4 mGy of SSDE. The lower dose limit for SAT and VAT combined was 1.5 mGy, which was equivalent to an estimated effective dose of 0.38 mSv. Alternatively, without noise reduction, SAT could not achieve acceptable accuracy even for images with a slice thickness of 5.25 mm, while VAT required noise reduction for images with a slice thickness of 1.25 mm, but could achieve acceptable accuracy without noise reduction for images with a slice thickness of 5.25 mm.

Imaging of Rheumatological Disorders.

Early diagnosis and treatment of many rheumatological conditions has become crucial in order that drug therapies can be started before irreversible structural damage occurs. Both MR imaging and ultrasound play a valid role in the pathway of many of these conditions. The imaging findings as well as relative merits are described in this article as well as limitations that must be kept in mind when interpreting the imaging. Both conventional radiography and computed tomography also add important information in certain cases and should not be forgotten.

Outcomes of the "BRCA Quality Improvement Dissemination Program": An initiative to improve patient receipt of cancer genetics services at five health systems.

OBJECTIVE: A quality improvement initiative (QII) was conducted with five community-based health systems' oncology care centers (sites A-E). The QII aimed to increase referrals, genetic counseling (GC), and germline genetic testing (GT) for patients with ovarian cancer (OC) and triple-negative breast cancer (TNBC). METHODS: QII activities occurred at sites over several years, all concluding by December 2020. Medical records of patients with OC and TNBC were reviewed, and rates of referral, GC, and GT of patients diagnosed during the 2 years before the QII were compared to those diagnosed during the QII. Outcomes were analyzed using descriptive statistics, two-sample t-test, chi-squared/Fisher's exact test, and logistic regression. RESULTS: For patients with OC, improvement was observed in the rate of referral (from 70% to 79%), GC (from 44% to 61%), GT (from 54% to 62%) and decreased time from diagnosis to GC and GT. For patients with TNBC, increased rates of referral (from 90% to 92%), GC (from 68% to 72%) and GT (81% to 86%) were observed. Effective interventions streamlined GC scheduling and standardized referral processes. CONCLUSION: A multi-year QII increased patient referral and uptake of recommended genetics services across five unique community-based oncology care settings.

A multicenter study of clinical impact of variant of uncertain significance reclassification in breast, ovarian and colorectal cancer susceptibility genes.

BACKGROUND: Clinical interpretation of genetic test results is complicated by variants of uncertain significance (VUS) that have an unknown impact on health but can be clarified through reclassification. There is little empirical evidence regarding VUS reclassification in oncology care settings, including the prevalence and outcomes of reclassification, and racial/ethnic differences. METHODS: This was a retrospective analysis of persons with and without a personal history of cancer carrying VUS (with or without an accompanying pathogenic or likely pathogenic [P/LP] variant) in breast, ovarian, and colorectal cancer predisposition genes seen at four cancer care settings (in Texas, Florida, Ohio, and New Jersey) between 2013 and 2019. RESULTS: In 2715 individuals included in the study, 3261 VUS and 313 P/LP variants were reported; 8.1% of all individuals with VUS experienced reclassifications and rates varied significantly among cancer care settings from 4.81% to 20.19% (overall p < 0.001). Compared to their prevalence in the overall sample, reclassification rates for Black individuals were higher (13.6% vs. 19.0%), whereas the rates for Asian individuals were lower (6.3% vs. 3.5%) and rates for White and Hispanic individuals were proportional. Two-year prevalence of VUS reclassification remained steady between 2014 and 2019. Overall, 11.3% of all reclassified VUS resulted in clinically actionable findings and 4.6% subsequently changed individuals' clinical managements. CONCLUSIONS: The findings from this large multisite study suggest that VUS reclassification alters clinical management, has implications for precision cancer prevention, and highlights the need for implementing practices and solutions for efficiently returning reinterpreted genetic test results.

Bone Marrow Lesions and Magnetic Resonance Imaging-Detected Structural Abnormalities in Patients With Midfoot Pain and Osteoarthritis: A Cross-Sectional Study.

OBJECTIVE: To compare magnetic resonance imaging (MRI)-detected structural abnormalities in patients with symptomatic midfoot osteoarthritis (OA), patients with persistent midfoot pain, and asymptomatic controls, and to explore the association between MRI features, pain, and foot-related disability. METHODS: One hundred seven adults consisting of 50 patients with symptomatic and radiographically confirmed midfoot OA, 22 adults with persistent midfoot pain but absence of radiographic OA, and 35 asymptomatic adults underwent 3T MRI of the midfoot and clinical assessment. MRIs were read for the presence and severity of abnormalities (bone marrow lesions [BMLs], subchondral cysts, osteophytes, joint space narrowing [JSN], effusion-synovitis, tenosynovitis, and enthesopathy) using the Foot Osteoarthritis MRI Score. Pain and foot-related disability were assessed with the Manchester Foot Pain and Disability Index. RESULTS: The severity sum score of BMLs in the midfoot was greater in patients with midfoot pain and no signs of OA on radiography compared to controls (P = 0.007), with a pattern of involvement in the cuneiform-metatarsal joints similar to that in patients with midfoot OA. In univariable models, BMLs (ρ = 0.307), JSN (ρ = 0.423), and subchondral cysts (ρ = 0.302) were positively associated with pain (P < 0.01). In multivariable models, MRI abnormalities were not associated with pain and disability when adjusted for covariates. CONCLUSION: In individuals with persistent midfoot pain but no signs of OA on radiography, MRI findings suggested an underrecognized prevalence of OA, particularly in the second and third cuneiform-metatarsal joints, where BML patterns were consistent with previously recognized sites of elevated mechanical loading. Joint abnormalities were not strongly associated with pain or foot-related disability.

Anterior Shoulder Instability.

The anatomy of the glenohumeral joint prioritizes mobility at the expense of stability and thus predisposes it to injury through dislocation. This article discusses the anatomical basis for instability and how it translates into patterns of injury, focusing on anterior instability. We suggest an approach to imaging the unstable shoulder and examine the imaging features seen in the context of anterior instability, along with consideration of postoperative appearances.

Clinical indications for image-guided interventional procedures in the musculoskeletal system: a Delphi-based consensus paper from the European Society of Musculoskeletal Radiology (ESSR)-part V, knee.

OBJECTIVES: Interventional procedures around the knee are widely adopted for treating different musculoskeletal conditions. A panel of experts from the Ultrasound and Interventional Subcommittees of the European Society of Musculoskeletal Radiology (ESSR) reviewed the existing literature to assess the evidence on image-guided musculoskeletal interventional procedures around the knee, with the goal of highlighting some controversies associated with these procedures, specifically the role of imaging guidance, as well as the efficacy of the medications routinely injected. METHODS: We report the results of a Delphi-based consensus of 53 experts in musculoskeletal radiology, who reviewed the published literature for evidence on image-guided interventional procedures around the knee to derive a list of pertinent clinical indications. RESULTS: A list of 10 statements about clinical indications of image-guided procedures around the knee was created by a Delphi-based consensus. Only two of them had the highest level of evidence; all of them received 100% consensus. CONCLUSIONS: Ultrasonography guidance is strongly recommended for intra-articular and patellar tendinopathy procedures to ensure the precision and efficacy of these treatments. Prospective randomized studies remain warranted to better understand the role of imaging guidance and assess some of the medications used for interventional procedures around the knee. KEY POINTS: • A list of 10 evidence-based statements on clinical indications of image-guided interventional procedures around the knee was produced by an expert panel of the ESSR. • Strong consensus with 100% agreement was obtained for all statements. • Two statements reached the highest level of evidence, allowing us to strongly recommend the use of ultrasonography to guide intra-articular and patellar tendon procedures to ensure higher accuracy and efficacy of these treatments.

Clinical indications for image-guided interventional procedures in the musculoskeletal system: a Delphi-based consensus paper from the European Society of Musculoskeletal Radiology (ESSR)-part VII, nerves of the lower limb.

OBJECTIVES: To perform a Delphi-based consensus on published evidence on image-guided interventional procedures for peripheral nerves of the lower limb (excluding Morton's neuroma) and provide clinical indications. METHODS: We report the results of a Delphi-based consensus of 53 experts from the European Society of Musculoskeletal Radiology who reviewed the published literature for evidence on image-guided interventional procedures offered around peripheral nerves in the lower limb (excluding Morton's neuroma) to derive their clinical indications. Experts drafted a list of statements and graded them according to the Oxford Centre for evidence-based medicine levels of evidence. Consensus was considered strong when > 95% of experts agreed with the statement or broad when > 80% but < 95% agreed. The results of the Delphi-based consensus were used to write the paper. RESULTS: Nine statements on image-guided interventional procedures for peripheral nerves of the lower limb have been drafted. All of them received strong consensus. Image-guided pudendal nerve block is safe, effective, and well tolerated with few complications. US-guided perisciatic injection of anesthetic provides good symptom relief in patients with piriformis syndrome; however, the addition of corticosteroids to local anesthetics still has an unclear role. US-guided lateral femoral cutaneous nerve block can be used to provide effective post-operative regional analgesia. CONCLUSION: Despite the promising results reported by published papers on image-guided interventional procedures for peripheral nerves of the lower limb, there is still a lack of evidence on the efficacy of most procedures. KEY POINTS: • Image-guided pudendal nerve block is safe, effective, and well tolerated with few complications. • US-guided perisciatic injection of anesthetic provides good symptom relief in patients with piriformis syndrome; however, the addition of corticosteroids to local anesthetics still has an unclear role. • US-guided lateral femoral cutaneous nerve block can be used to provide effective post-operative regional analgesia. The volume of local anesthetic affects the size of the blocked sensory area.

Clinical indications for image-guided interventional procedures in the musculoskeletal system: a Delphi-based consensus paper from the European Society of Musculoskeletal Radiology (ESSR)-part VI, foot and ankle.

OBJECTIVES: Clarity regarding accuracy and effectiveness for interventional procedures around the foot and ankle is lacking. Consequently, a board of 53 members of the Ultrasound and Interventional Subcommittees of the European Society of Musculoskeletal Radiology (ESSR) reviewed the published literature to evaluate the evidence on image-guided musculoskeletal interventional procedures around this anatomical region. METHODS: We report the results of a Delphi-based consensus of 53 experts from the European Society of Musculoskeletal Radiology who reviewed the published literature for evidence on image-guided interventional procedures offered around foot and ankle in order to derive their clinical indications. Experts drafted a list of statements and graded them according to the Oxford Centre for evidence-based medicine levels of evidence. Consensus was considered strong when > 95% of experts agreed with the statement or broad when > 80% but < 95% agreed. The results of the Delphi-based consensus were used to write the paper that was shared with all panel members for final approval. RESULTS: A list of 16 evidence-based statements on clinical indications for image-guided musculoskeletal interventional procedures in the foot and ankle were drafted after a literature review. The highest level of evidence was reported for four statements, all receiving 100% agreement. CONCLUSION: According to this consensus, image-guided interventions should not be considered a first-level approach for treating Achilles tendinopathy, while ultrasonography guidance is strongly recommended to improve the efficacy of interventional procedures for plantar fasciitis and Morton's neuroma, particularly using platelet-rich plasma and corticosteroids, respectively. KEY POINTS: • The expert panel of the ESSR listed 16 evidence-based statements on clinical indications of image-guided musculoskeletal interventional procedures in the foot and ankle. • Strong consensus was obtained for all statements. • The highest level of evidence was reached by four statements concerning the effectiveness of US-guided injections of corticosteroid for Morton's neuroma and PRP for plantar fasciitis.

Clinical indications for image-guided interventional procedures in the musculoskeletal system: a Delphi-based consensus paper from the European Society of Musculoskeletal Radiology (ESSR)-part IV, hip.

OBJECTIVES: Image-guided musculoskeletal interventional procedures around the hip are widely used in daily clinical practice. The need for clarity concerning the actual added value of imaging guidance and types of medications to be offered led the Ultrasound and the Interventional Subcommittees of the European Society of Musculoskeletal Radiology (ESSR) to promote, with the support of its Research Committee, a collaborative project to review the published literature on image-guided musculoskeletal interventional procedures in the lower limb in order to derive a list of clinical indications. METHODS: In this article, we report the results of a Delphi-based consensus of 53 experts who reviewed the published literature for evidence on image-guided interventional procedures offered in the joint and soft tissues around the hip in order of their clinical indications. RESULTS: Ten statements concerning image-guided treatment procedures around the hip have been collected by the panel of ESSR experts. CONCLUSIONS: This work highlighted that there is still low evidence in the existing literature on some of these interventional procedures. Further large prospective randomized trials are essential to better confirm the benefits and objectively clarify the role of imaging to guide musculoskeletal interventional procedures around the hip. KEY POINTS: • Expert consensus produced a list of 10 evidence-based statements on clinical indications of image-guided interventional procedures around the hip. • The highest level of evidence was only reached for one statement. • Strong consensus was obtained for all statements.

The interaction of competition and terrain on pacing during cross-county running races in junior athletes.

The aim of this study was to assess pacing during cross-country racing in relation to race length, surface-terrain and racing dynamics. Athletes (n = 148) competed for school teams (U15, U17, U20) over 2.9, 4.2, 6.3 km, respectively. The course lap (2.067 m) was timed using UHF-RFID and divided into six sections based on surface-terrain and length (549, 619, 207, 338, 150, 156m). Overall pace differed between races (4.56 ± 0.30, 4.42 ± 0.38, 4.40 ± 0.31 m∙s-1, p=0.042) but not for the top-20 of each race (p=0.174). Moreover, within lap pacing followed a repeated reverse-"J"-parabolic strategy for all races. Race length (no. of laps) and category affected pacing with regards to finish position banding (1st-10th, 11th-20th) where effect size differences showed large to extremely large (1.21 - >4.00) difference between top-10 and other bands. Exceptions to this included the finish sprint where it was typically trivial-moderate (<0.2-1.2) and in key areas where social facilitation occurred. Athlete/coaches need to be aware of between and within lap variations in pace/effort, the effects of race dynamics, and spectator influences, while all athletes need to be educated as part of their training to run their own optimal strategy for best performance.

Identification of Mep1a as a susceptibility gene for atherosclerosis in mice.

Atherosclerosis is the underlying cause of heart attack, ischemic stroke and peripheral arterial disease, and genetic factors involved remain mostly unidentified. We previously identified a significant locus on mouse chromosome 17 for atherosclerosis, Ath49, in an intercross between BALB/c and SM strains. Ath49 partially overlaps in the confidence interval with Ath22 mapped in an AKR × DBA/2 intercross. Bioinformatics analysis prioritized Mep1a, encoding meprin 1α metalloendopeptidase, as a likely candidate gene for Ath49. To prove causality, Mep1a-/-Apoe-/- mice were generated and compared with Mep1a+/+Apoe-/- mice for atherosclerosis development. Mep1a was found abundantly expressed in atherosclerotic lesions but not in healthy aorta and liver of mice. Mep1a-/- Apoe-/- mice exhibited significant reductions in both early and advanced lesion sizes. Loss of Mep1a led to decreased necrosis but increased macrophage and neutrophil contents in advanced lesions, reduced plasma levels of CXCL5 and an oxidative stress biomarker. In addition, Mep1a-/- mice had significantly reduced triglyceride levels on a chow diet. Thus, Mep1a is a susceptibility gene for atherosclerosis and aggravates atherosclerosis partially through action on oxidative stress and inflammation.

Radiologic Imaging of Metabolic and Endocrine Disorders as They Affect the Hand and Wrist.

Metabolic and endocrine disorders have systemic effects on the musculoskeletal system, frequently producing characteristic changes in the hand and wrist. Radiographs historically played an instrumental role in the diagnostic pathway of many of these disorders, but the myriad of endocrinologic tests readily available to current clinicians may suggest their importance has lessened. We disagree. Recognition of these often subtle features can avoid the expense and psychological impact of an inappropriate diagnostic work-up, as well as expediting the diagnosis of potentially unsuspected disease. The metabolic and endocrine disorders discussed here are based on the distinctive changes produced around the hand and wrist.

Inflammation and enhanced atherogenesis in the carotid artery with altered blood flow in an atherosclerosis-resistant mouse strain.

Ligation of the common carotid artery near its bifurcation in apolipoprotein E-deficient (Apoe-/- ) mice leads to rapid atherosclerosis development, which is affected by genetic backgrounds. BALB/cJ (BALB) mice are resistant to atherosclerosis, developing much smaller aortic lesions than C57BL/6 (B6) mice. In this study, we examined cellular events leading to lesion formation in carotid arteries with or without blood flow restriction of B6 and BALB Apoe-/- mice. Blood flow was obstructed by ligating the left common carotid artery near its bifurcation in one group of mice, and other group received no surgical intervention. Without blood flow interruption, BALB-Apoe-/- mice formed much smaller atherosclerotic lesions than B6-Apoe-/- mice after 12 weeks of Western diet (3,325 ± 1,086 vs. 81,549 ± 9,983 µm2 /section; p = 2.1E-7). Lesions occurred at arterial bifurcations in both strains. When blood flow was obstructed, ligated carotid artery of both strains showed notable lipid deposition, inflammatory cell infiltration, and rapid plaque formation. Neutrophils and macrophages were observed in the arterial wall of BALB mice 3 days after ligation and 1 week after ligation in B6 mice. CD4 T cells were observed in intimal lesions of BALB but not B6 mice. By 4 weeks, both strains developed similar sizes of advanced lesions containing foam cells, smooth muscle cells, and neovessels. Atherosclerosis also occurred in straight regions of the contralateral common carotid artery where MCP-1 was abundantly expressed in the intima of BALB mice. These findings indicate that the disturbed blood flow is more prominent than high fat diet in promoting inflammation and atherosclerosis in hyperlipidemic BALB mice.

Extradigital glomangiomyoma of the forearm mimicking peripheral nerve sheath tumour and thrombosed varicose vein.

Extradigital glomus tumour is uncommon, little-known outside of its subungual location, and may present without its classic triad of tenderness, cold sensitivity and paroxysmal pain. Imaging is non-specific and diagnosis is often delayed, sometimes for years, leading to unnecessary morbidity. Surgical excision is the treatment of choice, although technique depends on case specifics. Histological subtypes depend on the relative prominence of glomus cells, vascular structures and smooth muscle. The vast majority of glomus tumours are benign. We highlight the importance of considering extradigital glomus tumours when generating differential diagnoses of an atypical painful lesion in a variety of clinical specialties.

Deep Learning-based Quantification of Abdominal Subcutaneous and Visceral Fat Volume on CT Images.

RATIONALE AND OBJECTIVES: Develop a deep learning-based algorithm using the U-Net architecture to measure abdominal fat on computed tomography (CT) images. MATERIALS AND METHODS: Sequential CT images spanning the abdominal region of seven subjects were manually segmented to calculate subcutaneous fat (SAT) and visceral fat (VAT). The resulting segmentation maps of SAT and VAT were augmented using a template-based data augmentation approach to create a large dataset for neural network training. Neural network performance was evaluated on both sequential CT slices from three subjects and randomly selected CT images from the upper, central, and lower abdominal regions of 100 subjects. RESULTS: Both subcutaneous and abdominal cavity segmentation images created by the two methods were highly comparable with an overall Dice similarity coefficient of 0.94. Pearson's correlation coefficients between the subcutaneous and visceral fat volumes quantified using the two methods were 0.99 and 0.99 and the overall percent residual squared error were 5.5% and 8.5%. Manual segmentation of SAT and VAT on the 555 CT slices used for testing took approximately 46 hours while automated segmentation took approximately 1 minute. CONCLUSION: Our data demonstrates that deep learning methods utilizing a template-based data augmentation strategy can be employed to accurately and rapidly quantify total abdominal SAT and VAT with a small number of training images.

Foot and Leg Muscle Weakness in People With Midfoot Osteoarthritis.

OBJECTIVE: To compare foot and leg muscle strength in people with symptomatic midfoot osteoarthritis (OA) with asymptomatic controls, and to determine the association between muscle strength, foot pain, and disability. METHODS: Participants with symptomatic midfoot OA and asymptomatic controls were recruited for this cross-sectional study from general practices and community health clinics. The maximum isometric muscle strength of the ankle plantarflexors, dorsiflexors, invertors and evertors, and the hallux and lesser toe plantarflexors was measured using hand-held dynamometry. Self-reported foot pain and foot-related disability were assessed with the Manchester Foot Pain and Disability Index. Differences in muscle strength were compared between groups. Multivariable regression was used to determine the association between muscle strength, foot pain, and disability after adjusting for covariates. RESULTS: People with midfoot OA (n = 52) exhibited strength deficits in all muscle groups, ranging from 19% (dorsiflexors) to 30% (invertors) relative to the control group (n = 36), with effect sizes of 0.6-1.1 (P < 0.001). In those with midfoot OA, ankle invertor muscle strength was negatively and independently associated with foot pain (ß = -0.026 [95% confidence interval (95% CI) -0.051, -0.001]; P = 0.045). Invertor muscle strength was negatively associated with foot-related disability, although not after adjustment for depressive symptoms (ß = -0.023 [95% CI -0.063, 0.017]; P = 0.250). CONCLUSION: People with symptomatic midfoot OA demonstrate weakness in the foot and leg muscles compared to asymptomatic controls. Preliminary indications from this study suggest that strengthening of the foot and leg muscles may offer potential to reduce pain and improve function in people with midfoot OA.

Mononeuritis multiplex: an unexpectedly frequent feature of severe COVID-19.

The prolonged mechanical ventilation that is often required by patients with severe COVID-19 is expected to result in significant intensive care unit-acquired weakness (ICUAW) in many of the survivors. However, in our post-COVID-19 follow-up clinic we have found that, as well as the anticipated global weakness related to loss of muscle mass, a significant proportion of these patients also have disabling focal neurological deficits relating to multiple axonal mononeuropathies. Amongst the 69 patients with severe COVID-19 that have been discharged from the intensive care units in our hospital, we have seen 11 individuals (16%) with such a mononeuritis multiplex. In many instances, the multi-focal nature of the weakness in these patients was initially unrecognised as symptoms were wrongly assumed to relate simply to "critical illness neuromyopathy". While mononeuropathy is well recognised as an occasional complication of intensive care, our experience suggests that such deficits are surprisingly frequent and often disabling in patients recovering from severe COVID-19.

Effectively Measuring Exercise-Related Variations in T1ρ and T2 Relaxation Times of Healthy Articular Cartilage.

BACKGROUND: Determining the compositional response of articular cartilage to dynamic joint-loading using MRI may be a more sensitive assessment of cartilage status than conventional static imaging. However, distinguishing the effects of joint-loading vs. inherent measurement variability remains difficult, as the repeatability of these quantitative methods is often not assessed or reported. PURPOSE: To assess exercise-induced changes in femoral, tibial, and patellar articular cartilage composition and compare these against measurement repeatability. STUDY TYPE: Prospective observational study. POPULATION: Phantom and 19 healthy participants. FIELD STRENGTH/SEQUENCE: 3T; 3D fat-saturated spoiled gradient recalled-echo; T1ρ - and T2 -prepared pseudosteady-state 3D fast spin echo. ASSESSMENT: The intrasessional repeatability of T1ρ and T2 relaxation mapping, with and without knee repositioning between two successive measurements, was determined in 10 knees. T1ρ and T2 relaxation mapping of nine knees was performed before and at multiple timepoints after a 5-minute repeated, joint-loading stepping activity. 3D surface models were created from patellar, femoral, and tibial articular cartilage. STATISTICAL TESTS: Repeatability was assessed using root-mean-squared-CV (RMS-CV). Using Bland-Altman analysis, thresholds defined as the smallest detectable difference (SDD) were determined from the repeatability data with knee repositioning. RESULTS: Without knee repositioning, both surface-averaged T1ρ and T2 were very repeatable on all cartilage surfaces, with RMS-CV <1.1%. Repositioning of the knee had the greatest effect on T1ρ of patellar cartilage with the surface-averaged RMS-CV = 4.8%. While T1ρ showed the greatest response to exercise at the patellofemoral cartilage region, the largest changes in T2 were determined in the lateral femorotibial region. Following thresholding, significant (>SDD) average exercise-induced in T1ρ and T2 of femoral (-8.0% and -5.3%), lateral tibial (-6.9% and -5.9%), medial tibial (+5.8% and +2.9%), and patellar (-7.9% and +2.8%) cartilage were observed. DATA CONCLUSION: Joint-loading with a stepping activity resulted in T1ρ and T2 changes above background measurement error. EVIDENCE LEVEL: 2 TECHNICAL EFFICACY STAGE: 1 J. MAGN. RESON. IMAGING 2020;52:1753-1764.