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Objective Intermetatarsal bursae in the forefeet possess a synovial lining similar to joints and tendon sheaths. Inflammation of these bursae (intermetatarsal bursitis [IMB]) was recently identified as specific for early rheumatoid arthritis (RA). The present study was undertaken to determine if IMB is indeed an RA feature by assessing the following: 1) the association with other local inflammatory measures (synovitis, tenosynovitis, and osteitis), 2) the association with clinical signs, and 3) whether it responds to disease‐modifying antirheumatic drug (DMARD) therapy similarly to other local inflammatory measures. Methods One hundred fifty‐seven consecutive early RA patients underwent unilateral contrast‐enhanced 1.5T forefoot magnetic resonance imaging (MRI) at diagnosis. MRIs were evaluated for IMB presence and for synovitis, tenosynovitis, and osteitis in line with the RA MRI Scoring (RAMRIS) system (summed as RAMRIS inflammation). MRIs at 4, 12, and 24 months were evaluated for IMB presence and size in patients who had IMB at baseline and received early DMARD therapy. Logistic regression and generalized estimating equations were used. Anti–citrullinated protein antibody (ACPA) stratification was performed. Results Sixty‐nine percent of RA patients had ≥1 IMB. In multivariable analysis on bursa level, presence of IMB was independently associated with local presence of synovitis and tenosynovitis, with odds ratios (OR) of 1.69 (95% confidence interval [95% CI] 1.12, 2.57) and 2.83 (95% CI 1.80, 4.44), respectively, but not osteitis. On the patient level, IMB presence was most strongly associated with tenosynovitis (OR 2.92 [95% CI 1.62, 5.24]). IMB presence was associated with local joint swelling (OR 2.7 [95% CI 1.3, 5.3]) and tenderness (OR 1.7 [95% CI 1.04, 2.9]) independent of RAMRIS inflammation. During treatment, IMB size decreased between 0 and 12 months. This decrease associated with decrease in RAMRIS inflammation, which was driven by synovitis decrease. Within ACPA‐positive and ACPA‐negative RA, similar results were obtained. Conclusion IMB particularly accompanies inflammation of the synovial lining of joints and tendon sheaths, showed a similar treatment response after DMARD initiation, and associates with typical clinical signs. These findings suggest that IMB represents a frequently present novel RA feature of juxtaarticular synovial inflammation.

ObjectivesNational and international guidelines recommend prompt referral of patients presenting with inflammatory arthritis (IA), but general practitioners (GPs) feel uncertain in their proficiency to detect synovitis through joint examination, the method of choice to identify IA. Our objective was to develop and validate a rule composed of clinical characteristics to assist GPs and other physicians in identifying IA when in doubt.DesignSplit-sample derivation and validation study.SettingThe Leiden Early Arthritis Recognition Clinic (EARC), a screening clinic for patients in whom GPs suspected but were unsure of the presence of IA.Participants1288 consecutive patients visiting the EARC.Primary and secondary outcome measuresAssociations of clinical characteristics with presence of IA were determined using logistic regression in 644 patients, while validating the results in the other 644 patients (split-sample validation). To facilitate application in clinical practice, a simplified rule (with scores ranging from 0 to 7.5) was derived and validated.ResultsIA was identified by a rheumatologist in 41% of patients. In univariable analysis, male gender, age ≥60 years, symptom duration <6 weeks, morning stiffness >60 min, a low number of painful joints (1–3 joints), presence of patient-reported joint swelling and difficulty with making a fist were associated with IA in the derivation data set. Using multivariable analysis, a simplified rule consisting of these seven items was derived and validated, yielding an area under the receiver operator characteristic curve (AUC) of 0.74 (95% CI 0.70 to 0.78) in the derivation data set. Validation yielded an AUC of 0.71 (95% CI 0.67 to 0.75). Finally, the model was repeated to study predicted probabilities with a lower prevalence of inflammatory arthritis to simulate performance in primary care settings.ConclusionsOur rule, composed of clinical parameters, had reasonable discriminative ability for IA and could assist physicians in decision-making in patients with suspected IA, increasing appropriateness of healthcare utilisation.

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Objectives Intermetatarsal bursitis (IMB) represents juxta-articular synovial inflammation of the intermetatarsal bursae. Recent MRI studies identified IMB as feature of early RA, but whether IMB already occurs in the pre-arthritic phase is unknown. We performed a large MRI study in clinically suspect arthralgia (CSA) to assess the occurrence and prognostic value of IMB. Methods A total of 577 consecutive CSA patients underwent contrast-enhanced MRI of the forefoot, metacarpophalangeal joints and wrist. MRIs were evaluated for subclinical synovitis/tenosynovitis/osteitis in line with the RA MRI scoring system (summed as RAMRIS inflammation) and for IMB. IMB was considered present if uncommon in the general population at the same location (i.e. size scored above the 95th percentile in age-matched symptom-free controls). The relation of IMB with other MRI-detected subclinical inflammation (synovitis/tenosynovitis/osteitis) was studied. Cox-regression assessed the association with clinical arthritis development during median 25 months follow-up. ACPA stratification was performed. Results At presentation with CSA, 23% had IMB. IMB was more frequent in ACPA-positive than ACPA-negative CSA (47% vs 19%, P &lt; 0.001). Patients with IMB were more likely to also have subclinical synovitis [OR 3.4 (95% CI 1.8, 6.5)] and tenosynovitis [5.9(2.8, 12.6)]. IMB conferred higher risk of developing arthritis [HR 1.6(1.0–2.7) adjusted for other subclinical inflammation]. IMB-presence predicted arthritis development in ACPA-positive CSA [adjusted HR 2.2(1.0–4.7)], but not in ACPA-negative CSA-patients [0.8(0.4–1.7)]. Conclusion Approximately a quarter of CSA patients have IMB, which is frequently accompanied by subclinical synovitis and tenosynovitis. IMB precedes development of clinical arthritis, particularly in ACPA-positive CSA. These results reinforce the notion that juxta-articular synovial inflammation is involved in the earliest phases of RA development.

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Objectives The squeeze-test of metatarsophalangeal (MTP-)joints is frequently used, because it is easy and cheap. It is traditionally perceived as a test for synovitis. Besides classic intra-articular synovitis, also tenosynovitis and intermetatarsal bursitis (IMB) represent synovial inflammation, albeit juxta-articularly located. Both are frequently present in RA and occasionally in other arthritides. Therefore, we hypothesised that tenosynovitis and IMB contribute to a positive MTP-squeeze-test. Methods A cross-sectional study-design was used. 192 early arthritis patients and 693 clinically suspect arthralgia (CSA) patients underwent the MTP-squeeze-test and forefoot-MRI at first presentation. MRI-measurements in age-matched healthy controls were used to define positivity for synovitis, tenosynovitis and IMB. Logistic regression was used. Results In early arthritis patients synovitis (OR 4.8 (95%CI 2.5–9.5)), tenosynovitis (2.4 (1.2–4.7)) and IMB (1.7 (1.2–2.6)) associated with MTP-squeeze-test positivity. Synovitis (3.2 (1.4–7.2)) and IMB (3.9 (1.7–8.8)) remained associated in multivariable analyses. Of patients with a positive MTP-squeeze-test, 79% had synovitis or IMB: 12% synovitis, 15% IMB and 52% both synovitis and IMB. In CSA-patients, subclinical synovitis (3.0 (2.0–4.7)), tenosynovitis (2.7 (1.6–4.6)) and IMB (1.7(1.2–2.6)) associated with MTP-squeeze-test positivity, with the strongest association for synovitis in multivariable analysis. Of positive MTP-squeeze-tests, 39% had synovitis or IMB: 10% synovitis, 15% IMB and 13% both synovitis and IMB. Conclusion Besides synovitis, IMB contributes to pain upon compression in early arthritis, presumably due to its location between MTP-joints. This is the first evidence showing that MTP-squeeze-test positivity is not only explained by intra- but also juxta-articular inflammation.

MRI-detected inflammation around the extensor tendons of metacarpophalangeal (MCP-) joints is prevalent in RA and poses a markedly increased risk of RA development when present in arthralgia patients. Such inflammation is called ‘peritendinitis’ since anatomy literature reports no presence of a tenosynovial sheath at these tendons. However, the presence or absence of tenosynovium at these extensor tendons has never been studied. Therefore, an anatomical and histological study of extensor tendons at the MCP-joints of three embalmed human hands was performed. Immunohistochemical staining showed the presence of markers for synovial macrophages and fibroblast-like synoviocytes bordering a natural dorsal space next to the extensor tendon, suggesting the presence of a synovial lining. This implies that contrast-enhancement on MRI around extensor tendons at MCP-joints observed in early RA and pre-RA likely represents tenosynovitis and that inflammation of this synovial tissue is an early feature of RA.