Knee pain and inflammation in the infrapatellar fat pad estimated by conventional and dynamic contrast-enhanced magnetic resonance imaging in obese patients with osteoarthritis: a cross-sectional study.

OBJECTIVE: To investigate the association between knee pain and signs of inflammation in the infrapatellar fat pad (IPFP) in obese patients with knee osteoarthritis (KOA). DESIGN: In a cross-sectional setting, 3-T conventional contrast-enhanced (CE) magnetic resonance imaging (MRI) and dynamic contrast-enhanced (DCE)-MRI of KOA were analysed to quantify the extent of inflammation in the IPFP, and correlated (Spearman's rank correlation) to pain and other symptoms assessed via the Knee injury and Osteoarthritis Outcome Score (KOOS) (100 = no pain, 0 = extreme pain). The extent of inflammation in the IPFP was assessed according to the MRI Osteoarthritis Knee Score (MOAKS) using CE-MRI and by DCE-MRI perfusion variables. The perfusion variable, "Inflammation", was chosen as primary perfusion variable in the analysis. Intraclass correlation coefficients for the perfusion variables ranged from 0.81 to 0.99. RESULTS: MRI and clinical data were obtained in 95 patients. The typical patient was a woman (82%) with an average age of 65 years (SD 6.5) and a body mass index (BMI) of 32 kg/m(2) (SD 3.7). The bivariate association between KOOS pain and the DCE-MRI perfusion variable "Inflammation" showed a statistically significant correlation (r = -0.42, P < 0.0001). A statistically significant correlation was also found between KOOS pain and MOAKS Hoffa-synovitis (r = -0.21, P = 0.046). CONCLUSIONS: Perfusion variables on DCE-MRI reflecting the severity of inflammation in the IPFP and MOAKS Hoffa-synovitis were associated with the severity of pain in KOA. These results suggest that severe inflammation in the IPFP is associated with severe pain in KOA and that DCE-MRI is a promising method to study the impact of inflammation in KOA.

Validity and reliability of 3D US for the detection of erosions in patients with rheumatoid arthritis using MRI as the gold standard.

PURPOSE: To test the reliability and validity of a 3D US erosion score in RA using MRI as the gold standard. MATERIALS AND METHODS: RA patients were examined with 3D US and 3 T MRI over the 2nd and 3rd metacarpophalangeal joints. 3D blocks were evaluated by two investigators. The erosions were estimated according to a semi-quantitative score (SQS) (0 - 3) and a quantitative score (QS) (mm²). MRI was evaluated according to the RAMRIS score. For the estimation of reliability, intra-class correlation coefficients (ICC) were used. Validity was tested using Spearman's rho (rs). The sensitivity and specificity were also calculated. RESULTS: 28 patients with RA were included. The ICC for the inter-observer reliability in the QS was 0.41 and 0.13 for the metacarpal bone and phalangeal bone, respectively, and 0.86 and 0.16, respectively, in the SQS.  The ICC for the intra-observer reliability in the QS was 0.75 and 0.48 for the metacarpal bone and phalangeal bone, respectively, and 0.83 and 0.60, respectively, in the SQS.  The correlation with MRI for the metacarpal bone was significant, with values of 0.73 (p = 0.0001) (SQ) and 0.74 (p = 0.0001) (SQS). For the phalangeal bone, bad correlation was found: 0.28 (p = 0.145) (SQ) and 0.26 (p = 0.57) (SQS). The sensitivity and specificity for the metacarpal bone were 86 % and 85 % respectively. For the phalangeal bone they were 60 % and 97 %, respectively. CONCLUSION: Good inter- and intra-observer reliability and correlation with MRI were seen in the assessment of erosions with 3D US in the metacarpal bone, while the results were low and insignificant for the phalangeal bone, indicating that 3D US still has room for improvement.