The role of PET in a clinically silent and ultrasound negative synovitis in the course of rheumatoid arthritis - a case report.

We present a case report of a rheumatoid arthritis patient, who underwent a PET scan, which revealed inflammation of multiple joints, which was missed by both physical and ultrasound examinations. A 55-year old woman with a long-term rheumatoid arthritis, who had undergone arthroplasty of the left knee in the past, consulted with the rheumatologist for pain in the left knee. The physical examination revealed signs of inflammation in the left knee and right elbow. The inflammatory parameters were high. Ultrasound showed intraarticular effusion without signs of active synovitis in the left knee. The ultrasound assessment of the other joints (hands, wrists and feet) was also negative for active synovitis, while positron-emission tomography (PET) revealed increased glucose metabolism at the level of the medial side of the left knee, left radio-ulno-carpal joint, I-II-III metacarpo-phalangeal joints bilaterally, right II metatarso-phalangeal joint, and left II-III metatarso-phalangeal joints. This case report demonstrates that PET might be more sensitive than ultrasound in detecting subclinical joint inflammation.

Accuracy of synovial fluid analysis compared to histology for the identification of calcium pyrophosphate crystals: an ancillary study of the OMERACT US Working Group - CPPD subgroup.

The aim of this study was to evaluate the accuracy of synovial fluid analysis in the identification of calcium pyrophosphate dihydrate crystals compared to microscopic analysis of joint tissues as the reference standard. This is an ancillary study of an international, multicentre cross-sectional study performed by the calcium pyrophosphate deposition disease (CPPD) subgroup of the OMERACT Ultrasound working group. Consecutive patients with knee osteoarthritis (OA) waiting for total knee replacement surgery were enrolled in the study from 2 participating centres in Mexico and Romania. During the surgical procedures, synovial fluid, menisci and hyaline cartilage were collected and analysed within 48 hours from surgery under transmitted light microscopy and compensated polarised light microscopy for the presence/absence of calcium pyrophosphate crystals. All slides were analysed by expert examiners on site, blinded to other findings. A dichotomic score (absence/ presence) was used for scoring both synovial fluid and tissues. Microscopic analysis of knee tissues was considered the gold standard. Sensitivity, specificity, accuracy, positive and negative predictive values of synovial fluid analysis in the identification of calcium pyrophosphate crystals were calculated. 15 patients (53% female, mean age 68 yo ± 8.4) with OA of grade 3 or 4 according to Kellgren-Lawrence scoring were enrolled. 12 patients (80%) were positive for calcium pyrophosphate crystals at the synovial fluid analysis and 14 (93%) at the tissue microscopic analysis. The overall diagnostic accuracy of synovial fluid analysis compared with histology for CPPD was 87%, with a sensitivity of 86% and a specificity of 100%, the positive predictive value was 100% and the negative predictive value was 33%. In conclusion synovial fluid analysis proved to be an accurate test for the identification of calcium pyrophosphate dihydrate crystals in patients with advanced OA.

Global ultrasound assessment of structural lesions in osteoarthritis: a reliability study by the OMERACT ultrasonography group on scoring cartilage and osteophytes in finger joints.

OBJECTIVE: Ultrasonography is sensitive for the evaluation of cartilage pathology and degree of osteophytes in patients with hand osteoarthritis (OA). High consistency of assessments is essential, and the OMERACT (Outcome Measures in Rheumatology) ultrasonography group took the initiative to explore the reliability of a global ultrasonography score in patients with hand OA using semiquantitative ultrasonography score of cartilage and osteophytes in finger joints. METHODS: Ten patients with hand OA were examined by 10 experienced sonographers over the course of two days. Semiquantitative scoring (0-3) was performed on osteophytes (carpo-metacarpal 1, metacarpo-phalangeal (MCP) 1-5, proximal interphalangeal 1-5 and distal interphalangeal 2-5 joints bilaterally with an ultrasonography atlas as reference) and cartilage pathology (MCP 2-5 bilaterally). A web-based exercise on static cartilage images was performed a month later. Reliability was assessed by use of weighted κ analyses. RESULTS: Osteophyte scores were evenly distributed, and the intraobserver and interobserver reliabilities were substantial to excellent (κ range 0.68-0.89 and mean κ 0.65 (day 1) and 0.67 (day 2), respectively). Cartilage scores were unevenly distributed, and the intraobserver and interobserver reliability was fair to moderate (κ range 0.46-0.66 and mean κ 0.39 (day 1) and 0.33 (day 2), respectively). The web-based exercise showed acceptable agreement for cartilage being normal (κ 0.47) or with complete loss (κ 0.68), but poor for the intermediate scores (κ 0.22-0.30). CONCLUSIONS: Use of the present semiquantitative ultrasonography scoring system for cartilage pathology in hand OA is not recommended (while normal or total loss of cartilage may be assessed). However, the OMERACT ultrasonography group will endorse the use of semiquantitative scoring of osteophytes with the ultrasonography atlas as reference.

Ultrasound in the diagnosis of calcium pyrophosphate dihydrate deposition disease. A systematic literature review and a meta-analysis.

OBJECTIVE: Ultrasonography (US) demonstrated to be a promising tool for the diagnosis of calcium pyrophosphate dihydrate deposition disease (CPPD). The aim of this systematic literature review (SLR) was to collect the definitions for the US elementary lesions and to summarize the available data about US diagnostic accuracy in CPPD. METHODS: We systematically reviewed all the studies that considered US as the index test for CPPD diagnosis without restrictions about the reference test or that provided definitions about US identification of CPPD. Sensitivity and specificity were calculated for each study and definitions were extrapolated. Subgroup analyses were planned by anatomical site included in the index text and different reference standards. RESULTS: Thirty-seven studies were included in this review. All the studies were eligible for the collection of US findings and all definitions were summarized. US description of elementary lesions appeared heterogeneous among the studies. Regarding US accuracy, 13 articles entered in the meta-analysis. Considering each joint structure, the sensitivity ranged between 0.77 (0.63-0.87) and 0.34 (0.16-0.58) while the specificity varies between 1.00 (0.89-1.00) and 0.92 (0.16-1.00). Considering the reference standards used, the sensibility ranged between 0.34 (0.02-0.65) and 0.87 (0.76-0.99) while specificity ranged between 0.84 (0.52-1.00) and 1.00 (0.99-1.00). CONCLUSION: US is potentially a useful tool for the diagnosis of CPPD but universally accepted definitions and further testing are necessary in order to assess the role of the technique in the diagnostic process.

Atlas-based knee osteophyte assessment with ultrasonography and radiography: relationship to arthroscopic degeneration of articular cartilage.

OBJECTIVES: To investigate intra- and inter-reader agreement of ultrasonography (US) and conventional radiography (CR) for the evaluation of osteophyte presence and size within the tibiofemoral joint. In addition, to correlate these findings with arthroscopic degeneration of the articular cartilage. METHOD: Forty adult patients with knee pain were enrolled in this study. Knee CR and US scanning of the medial and lateral bone margins were performed on all patients. A novel atlas for the US grading of knee osteophytes was used in the evaluation. The number and size of the osteophytes were evaluated semi-quantitatively in two rounds from both the CR images (four readers) and the US images (14 readers). The Noyes grading system was used for the evaluation of arthroscopic degeneration of the articular cartilage in 26 patients. RESULTS: On average, intra- and inter-reader US and CR agreement was substantial and comparable to each other (κ = 0.60-0.72). US detected more osteophytes than CR at both the medial (65% vs. 48%) and lateral (70% vs. 60%) compartments. A statistically significant correlation between CR- or US-based osteophyte and arthroscopy grades was observed only for US at the medial compartment (rs = 0.747, p < 0.001). CONCLUSIONS: The detection of knee osteophytes using the novel US atlas is as reproducible as reading conventional radiographs. US is more sensitive to detect knee osteophytes than CR. Furthermore, osteophytes detected with US correlate significantly with arthroscopic cartilage changes at the medial knee compartment whereas those detected by CR do not.

Radiologists and rheumatologists on performing and reporting shoulder ultrasound: from disagreement to consensus.

Shoulder pain is a common condition in the rheumatologist's practice, yet there are no guidelines on how to report shoulder ultrasound (US) examinations. The aim of this study was to compare scanning and reporting techniques performed by radiologists and rheumatologists and identify any discrepancies between the two. The participants in this study were five rheumatologists and two radiologists specialized in musculoskeletal US. The study was divided in 2 phases. In the first phase, each participant performed an US of 3 patients and reported the findings without knowing the patient diagnosis and the findings reported by the other operators. Other three investigators reported the US technique of each operator. Reports and images were subsequently compared to identify any discrepancies and reach consensus on a common approach. In the second phase, a US scan was performed on a fourth patient in a plenary session to assess feasibility and efficacy of the common approach The US scanning technique was similar for all operators. The differences in reporting emerged in the description of the rotator cuff disease. Radiologists provided a detailed description of lesions (measurements along 2 axis and scoring of lesions), whereas rheumatologists described carefully the inflammatory changes. The experts concluded that lesions should be measured along 2 axes and the grade of degeneration and the age of the lesion should be reported. Another difference emerged in the description of the irregularities of the bone surface. The experts concluded that the term erosion should be used only when an inflammatory joint disease is suspected. This study led to the clarification of some inconsistencies in US reporting, and represented an interesting collaborative experience between radiologists and rheumatologists.

EFSUMB minimum training requirements for rheumatologists performing musculoskeletal ultrasound.

In order to optimize and standardize musculoskeletal ultrasonography education for rheumatologists, there is a need for competency assessments addressing the required training and practical and theoretical skills. This paper describes how these competency assessments for rheumatologists were developed and what they contain.

Diffusion and applications of musculoskeletal ultrasound in Italian Rheumatology Units.

The Musculoskeletal Ultrasound Study Group of the Italian Society of Rheumatology (SIR) was founded during the 68th SIR Congress, on November 2011. The request of activation of this group was based on the increasing interest and the widespread diffusion of ultrasound in the scientific rheumatology community and on the solid experience of some Italian rheumatologists in the field. The aims of the Study Group are to stimulate the applications and use of ultrasound in the clinical practice at the level of the Italian rheumatology units and, in addition, to develop research projects at a national level...

The reliability of musculoskeletal ultrasound in the detection of cartilage abnormalities at the metacarpo-phalangeal joints.

OBJECTIVE: To assess the reliability of ultrasound (US) in detecting cartilage abnormalities at the metacarpo-phalangeal (MCP) joints in people with cartilage pathology. METHODS: Nine expert ultrasonographers initially achieved consensus on definitions and scanning protocols. They then examined the second to fifth MCP joints of the dominant hand of eight people with hand osteoarthritis (OA). US examinations were conducted in two rounds, with independent blinded evaluations of cartilage lesions. Global cartilage abnormalities were assessed by applying a dichotomous (presence/absence) score; in addition, the following lesions were evaluated using the same scoring system: loss of anechoic structure and/or thinning of the cartilage layer, and irregularities and/or loss of sharpness of at least one cartilage margin. Reliability was assessed using kappa (k) coefficients. RESULTS: Thirty-two joints were examined. Intra-observer k values ranged from 0.52 to 1 for global cartilage abnormalities; k values ranged from 0.54 to 0.94 for loss of anechoic structure and/or thinning of cartilage layer and from 0.59 to 1 for irregularities and/or loss of sharpness of at least one cartilage margin. Values of k for inter-observer reliability were 0.80 for global cartilage abnormalities, 0.62 for loss of anechoic structure and/or thinning of cartilage layer, and 0.39 for irregularities and/or loss of sharpness of at least one cartilage margin. CONCLUSION: US is a reliable imaging modality for the detection of cartilage abnormalities in patients with cartilage pathology in the MCP joints. The analysis of specific cartilage measures showed more variable results that may be improved by modifying definitions and further standardization of US techniques.

Role of scintigraphy with 99mTc-infliximab in predicting the response of intraarticular infliximab treatment in patients with refractory monoarthritis.

PURPOSE: The rationale for the present study was to evaluate the predictive role of (99m)Tc-infliximab scintigraphy in therapy decision-making in patients with refractory monoarthritis and also candidates for intraarticular (IA) infliximab treatment. METHODS: We studied 12 patients (5 with rheumatoid arthritis and 7 with spondyloarthropathy) with active monoarthritis (11 knees and 1 ankle) that had lasted for at least 3 months. Patients were evaluated clinically and ultrasonographically at baseline and 12 weeks after IA administration of infliximab. At the same time-points, (99m)Tc-infliximab scintigraphy was performed: planar anterior and posterior images of arthritic joints were acquired at 6 and 20 h after injection and target-to-background (T/B) ratios were calculated. RESULTS: After treatment, a significant improvement in clinical and ultrasonographic parameters was recorded in six patients. Three patients had a partial response and three did not respond. Regarding scintigraphic evaluation, the T/B ratio analysis showed a significantly higher uptake in affected than in nonaffected joints before therapy (1.78 ± 0.46 vs. 1.29 ± 0.27, p = 0.006 at 6 h; 2.05 ± 0.50 vs. 1.41 ± 0.36 at 20 h, p = 0.002), and mean uptake at 20 h was also significantly higher than at 6 h (p = 0.0004). Scintigraphy showed a significant decrease in posttherapy T/B ratios of the affected joints (p = 0.0001 at 6 h and p = 0.0001 at 20 h), indicating a reduction in TNF into the affected joints. Most importantly, responders showed a significantly higher percentage increase in pretherapy uptake from 6 h to 20 h in the affected joints than nonresponders (p = 0.00001). CONCLUSION: The results of the present investigation suggest that (99m)Tc-infliximab scintigraphy could be a useful tool to predict the clinical response to IA infliximab treatment in patients with refractory monoarthritis.

Ultrasound imaging for the rheumatologist XXXVII. Sonographic assessment of the hip in ankylosing spondylitis patients.

OBJECTIVES: To investigate the prevalence of ultrasound (US) detectable inflammation in hips of patients with ankylosing spondylitis (AS) and the relationship between US and measures of disease activity and severity. METHODS: Consecutive patients with AS attending the rheumatology units involved in this study were enrolled. Clinical and demographical data were recorded. US examination of bilateral hips was performed at the same time, evaluating anterior longitudinal scan to search for synovial hypertrophy (SH), joint effusion (JE) or power Doppler (PD) positive synovitis. RESULTS: A total of 56 patients were included, median age (interquartile range, IQR) 49 (39, 59.5), median disease duration 98 (72, 204) months, 80.3% were treated with TNF-α inhibitors, median BASDAI 2.65 (1.96, 3.95), 30.3% had hip tenderness. US JE was found in 26.7% of patients, US SH in 16%, no patient had detectable PD. The concordance between clinical findings and US abnormalities was moderate, with a kappa of 0.44. Patients with detectable US abnormalities had higher median visual analogue scale (VAS) pain and C-reactive protein (CRP), while there was no significant association with other measures of disease activity and disability. In the subgroup of patients with no hip tenderness, US alterations were still significantly related to higher CRP levels, while in patients with hip tenderness and no US abnormalities CRP was not higher than in the asymptomatic patients. CONCLUSIONS: US assessment of hip joint in AS patients can be considered of value, as suggested by the correlation with relevant clinical and laboratory measures. In asymptomatic patients, US examination might provide further information on subclinical involvement.

Ultrasound imaging for the rheumatologist XXXIX. Sonographic assessment of the hip in fibromyalgia patients.

Fibromyalgia syndrome (FMS) is a common form of non-inflammatory rheumatism within the general population with symptoms often mimicking those of arthritis or muscle disorders. Arthralgic symptoms in the region of the hip are commonly mentioned by patients with FMS and one of the diagnostic trigger points for the condition is found around the greater trochanter. To date, no formal imaging studies using ultrasound (US) have been performed in FMS. This study describes the correlation between clinical and US findings in patients presenting with primary FMS to rheumatology clinics. In the majority of the patients, no significant pathological US abnormalities were detected.

Which knee and probe position determines the final diagnosis of knee inflammation by ultrasound? Results from a European multicenter study.

PURPOSE: To investigate which knee and probe position best identifies knee inflammation and to determine a cut-off level for abnormal synovial effusion. MATERIALS AND METHODS: 18 experienced sonographers (all rheumatologists) performed ultrasound examinations of the knee joint in patients with knee symptoms and in healthy controls. Each sonographer performed longitudinal suprapatellar ultrasound scans using 9 different configurations at each knee: Midline, parapatallar lateral and parapatellar medial from midline in neutral position (0°) with and without quadriceps muscle contraction and in 30° flexion of the knee. The presence of synovial effusion (SE), the effusion measured in millimeters and the presence of synovial hypertrophy (SH) was noted. RESULTS: A total of 298 knees of 149 subjects (129 patients and 20 controls) were examined. The detection of SH is more sensitive and specific than the detection of SE, independently of the knee and probe position, for the final diagnosis of abnormality. The detection of both synovial hypertrophy and effusion in the knee in neutral position (0°) with quadriceps contraction and with the probe in the midline position, are the best independent predictors for knee abnormalities. Knee effusion > 3.2 mm measured with the probe in the lateral aspect of the knee is the best diagnostic characteristics for predicting pathological SE. CONCLUSION: The best combination for detecting SH and SE is obtained by placing the probe in the midline position with the knee in 0° with quadriceps contraction. A cut-off value for pathological effusion may be obtained in the lateral aspect of the knee.

Ultrasound imaging for the rheumatologist XXXIV. Sonographic assessment of the painful foot.

The foot is increasingly the focus of attention for rheumatologists when assessing patients presenting to a clinic and may represent underlying intra-articular inflammatory pathology or involvement of the surrounding soft tissues. This study describes the correlation between clinical and ultrasound (US) findings in patients presenting with a variety of rheumatic disorders linked with foot pain. Poor correlation was found between conventional clinical examination and US in cases with joint inflammation, tendonitis and, more particularly, those cases with enthesopathy.

Ultrasound imaging for the rheumatologist XXXIII. Sonographic assessment of the foot in early arthritis patients.

OBJECTIVES: To investigate the ability of ultrasonography (US) to detect synovitis in metatarsophalangeal joints (MTP) in patients with suspicion of early arthritis, and to discriminate between diagnoses. METHODS: Patients referred to early arthritis clinics for differential diagnosis were enrolled, and clinical and laboratory measures were recorded. Ultrasonography of MTPs was performed searching for synovial hypertrophy (SH), joint effusion (JE) and power Doppler (PD), graded from 0 to 3 on a semi-quantitative scale. Patients were classified according to definite classification criteria, or as undifferentiated arthritis or non-inflammatory pathology. US findings were compared across different diagnoses and diagnostic accuracy was calculated taking clinical diagnosis as reference. RESULTS: Out of 427 patients (71% rheumatoid arthritis (RA), 20% undifferentiated arthritis (UA), 15% spondyloarthritides (SpA), 13% non-inflammatory), 307 (71.9%) showed SH, 120 (25.5%) JE, 77 (18.0%) PD. RA patients had median JE, SH and PD scores significantly higher than non-inflammatory and other diseases. Patient with UA and SpA had higher scores of SH and JE compared to non-inflammatory, no significant differences were present among different diagnosis. In RA, SH and JE were more frequently detected in the second MTP, and PD in the fifth. Crystal-related arthritis showed a tendency towards a more frequent involvement of the first MTP. The diagnostic accuracy of single US measures was moderate, but the detection of a PD of 2 or more provided a high specificity for the diagnosis of RA. CONCLUSIONS: US can be used as additional information in patients evaluated in an early arthritis setting. High scores of JE, SH and PD, together with the pattern of involvement are suggestive of RA.

Ultrasound imaging for the rheumatologist. XXXII. Sonographic assessment of the foot in patients with psoriatic arthritis.

Psoriatic arthritis (PsA) is an arthropathy associated with psoriasis, which is part of the spondyloarthropathy family, and which may present with various forms, from mono-oligoarthritis to symmetric polyarthritis mimicking rheumatoid arthritis. In longstanding disease, the symmetric polyarthritis is the most common pattern of PsA, involving the small joints of hands, feet (the involvement of which seems to be very common, ranging from 50 to 100% of patients), wrists, ankles and knees. Other common features are represented by the inflammation of enthesis and tendons. Its exact prevalence, in Italy, should be about 30% in psoriatic subjects or 0.42% when considering the general population. The aims of our study were to investigate, by US examination, the prevalence and the features of foot involvement in PsA and to describe their correlations with clinical findings. Ultrasound (US) examinations were performed using a Logiq 9 (General Electric Medical Systems, Milwaukee, WI) equipped with a multifrequency linear probe, working at 14 MHz. One hundred and eighty feet were investigated in a total of 101 patients. Prior to US assessment, all patients underwent a clinical examination by an expert rheumatologist who recorded the presence/absence of pain, tenderness (detected by palpation and/or active or passive mobilisation of the feet) and swelling. US finding indicative of metatarsophalangeal joint inflammation were obtained in 77 (76.2%) patients, while only 34 (33.7%) patients were positive to the clinical examination. This study demonstrates that US detected a higher number of inflamed joints with respect to clinical assessment in PsA patients.

Exploratory data analysis on the effects of non pharmacological treatment for knee osteoarthritis.

OBJECTIVES: Osteoarthritis (OA) is a chronic rheumatic disease characterized by progressive cartilage destruction mediated by cytokines and other molecules. Chondrocyte activity and metabolism have attracted interest as targets of drug intervention, and spa-therapy can influence the serum levels of several cytokines. We investigated the effects of spa-therapy on clinical and ultrasonographic (US) findings and serum levels of cartilage oligomeric matrix protein (COMP) and several cytokines, chemokines, and growth factors in a prospective cohort of patients with symptomatic knee OA. METHODS: Patients (n=53) with primary symptomatic knee OA were treated for 12 consecutive days with locally applied mud-packs. Assessments were made at baseline, immediately after completion of the treatment cycle, and 6 and 12 months after completion of treatment. They included visual analogue scale (VAS) ratings of pain, the Lequesne algofunctional index for knee OA, and US with calculation of a semiquantitative score that expressed the severity of the local inflammatory process. Serum levels of 27 cytokines (including interferon--inducible protein-10 [IP-10]), chemokines, and growth factors were measured with multiplex bead-based immunoassays, and COMP levels were determined by ELISA. RESULTS: US scores, VAS pain ratings, and Lequesne indexes indicated significant improvement after spa-therapy and at the 6- and 12-month follow-ups. Serum IP-10 levels also dropped significantly (p=0.0035), and this reduction was positively correlated with improvement of the Lequesne index (p=0.031). CONCLUSIONS: In patients with knee OA, spa-therapy can modulate serum levels of proinflammatory cytokines/chemokines and produce improvements in joint pain and function that persists for up to 1 year.

Ultrasound imaging for the rheumatologist XXX. Sonographic assessment of the painful knee.

The knee joint is a frequent focus of attention for rheumatologists when assessing patients presenting to a clinic and may represent underlying intra-articular inflammatory pathology or involvement of the surrounding soft tissues. This study describes the correlation between clinical and ultrasound findings in patients presenting with a variety of rheumatic disorders and knee pain. US imaging provides for a sensitive and detailed identification of different intra- and peri-articular pathology responsible for knee pain.

Ultrasound imaging for the rheumatologist. XXVIII. Impact of sonographic knee joint involvement in recent-onset inflammatory polyarthritis.

OBJECTIVES: To assess the impact of the knee joint inflammation, detected by ultrasonography (US), on functional disability in patients with recent-onset inflammatory polyarthritis (IP). METHODS: We included patients who had IP for less than 12 months and who had more than 5 swollen joints. All patients were assessed clinically at baseline. US was used to identify joint inflammation at multiple joint sites including: hands, wrists, elbows, shoulders, knees, ankles and feet. Joint group involvement was defined when at least one joint showed intra-articular signs of inflammation (synovial fluid abnormalities and/or synovial hypertrophy), according to the OMERACT definitions. Functional disability was measured using the health assessment questionnaire (HAQ) score. All patients with complete clinical and US data were included in the analysis. RESULTS: Patients with US knee involvement showed more active and severe disease at baseline. The mean difference of HAQ between patients with and without US knee inflammation was 0.42 (95%CI 0.22, 0.62; p<0.001). This difference was still clinically and statistically significant even after controllino for disease extension and pattern of joint involvement. US shoulder involvement was also significantly and independently associated with higher mean HAQ scores. CONCLUSIONS: US knee involvement is associated with higher disability in IP at first presentation. US is a good tool to help in the differentiation of patients with recent-onset IP with different disease severity.

Ultrasound imaging for the rheumatologist XXVI. Sonographic assessment of the knee in patients with psoriatic arthritis.

Psoriatic arthritis (PsA) is an arthropathy associated to psoriasis, which is part of the spondyloarthropathy family, and which may present with various forms, from mono-oligoarthritis to symmetric polyarthritis mimicking rheumatoid arthritis. In longstanding disease, the symmetric polyarthritis is the most common pattern of PsA, involving small joint of hands, feet, wrists, ankles and, very frequently, knees. Other common features are represented by the inflammation of enthesis and tendons. Ultrasound (US) examinations were performed using a Logiq 9 (General Electric Medical Systems, Milwaukee, WI) equipped with a multifrequency linear probe, working at 10-14 MHz. One-hundred and sixty-six knee joints were investigated in a total of 83 patients. Prior to US assessment, all patients underwent a clinical examination by an expert rheumatologist who recorded the presence/absence of pain, tenderness (detected by palpation and/or active or passive mobilisation of the knee), and knee swelling. Sixty-two (74.7%) knee joints were found clinically involved, while at least one US finding indicative of joint inflammation was obtained in 70 (84.3%) knee joints. In the 59% of the patients we noticed synovial hypertrophy. Enthesitis was present in 39.7% of the subjects studied. This study demonstrated that US detected a higher number of inflamed knee joints and enthesis with respect to clinical assessment in PsA patients.