Quantitatively Measured Infrapatellar Fat Pad Signal Intensity Alteration is Associated with Joint Effusion-Synovitis in Knee Osteoarthritis

Background: Abnormal infrapatellar fat pad (IPFP) plays a detrimental role in knee osteoarthritis (OA) by producing pro-inflammatory cytokines. IPFP may interact with synovium because of their adjacent anatomical positions; however, whether abnormal IPFP can contribute to effusion-synovitis in knee OA is unclear.Methods: Among 255 knee OA patients, IPFP signal intensity alteration represented by four measurement parameters [standard deviation of IPFP signal intensity (IPFP sDev), upper quartile value of IPFP high signal intensity region (IPFP UQ (H)), ratio of IPFP high signal intensity region volume to whole IPFP volume (IPFP percentage (H)), and clustering factor of IPFP high signal intensity (IPFP clustering factor (H))] was measured quantitatively at baseline and two-year follow-up using magnetic resonance imaging (MRI). Effusion-synovitis of the suprapatellar pouch and other cavities were measured both quantitatively and semi-quantitatively as effusion-synovitis volume and effusion-synovitis score at baseline and two-year follow-up using MRI. Mixed-effects models were used to assess the associations between IPFP signal intensity alteration and effusion-synovitis over two years.Results: In multivariable analyses, all four parameters of IPFP signal intensity alteration were positively associated with total effusion-synovitis volume and effusion-synovitis volumes of the suprapatellar pouch and of other cavities over two years (all P＜0.05). They were also associated with the semi-quantitative measure of effusion-synovitis except for IPFP percentage (H) with effusion-synovitis in other cavities. Conclusion: Quantitatively measured IPFP signal intensity alteration is positively associated with joint effusion-synovitis in people with knee OA, suggesting that IPFP signal intensity alteration may contribute to effusion-synovitis and a coexistent pattern of these two imaging biomarkers could exist in knee OA patients.

Recurrent hemarthrosis after total knee arthroplasty in rheumatoid arthritis successfully treated with selective embolization: A case report

Recurrent hemarthrosis after total knee arthroplasty is a rare complication. This usually occurs in osteoarthritis, but is relatively rare in rheumatoid arthritis. This is a report of recurrent hemarthrosis after total knee arthroplasty in a rheumatoid arthritis patient. An 85-year-old woman with rheumatoid arthritis had received total knee arthroplasty without acute complications. At 6 months after surgery, the first hemarthrosis occurred and an initial conservative treatment failed. Contrast computed tomography showed prominent synovial enhancement in the superior lateral suprapatellar pouch. Selective catheterization revealed an abnormal hyperemic blush supplied from the branches of the superior lateral genicular artery. After embolization with N-butyl-2-cyanoacrylate, abnormal staining of the synovium diminished and knee swelling and pain disappeared without complications. Selective embolization is favorable for successful treatment of recurrent hemarthrosis after total knee arthroplasty in patients with rheumatoid arthritis.

Lipoma arborescens: a rare cause of clicking in the knee

Lipoma arborescens (LA) is a rare condition with synovial membrane lipomatous proliferation. It most commonly affects the knee joint, in the suprapatellar pouch. It can present as a painful knee with an effusion. Diagnosis is via MRI demonstrating a synovial mass with frond-like appearance, and histology showing mature adipose cells, with an overlying synovial membrane. Treatment options include non-operative measures with analgesia, or operative intervention to resect the lesion. We describe a unique case of LA present in the anterolateral knee joint, presenting with persistent painful clicking in the knee. The patient underwent an open total resection of the lesion, with resolution of symptoms.

Lipoma Arborescens of the Knee: Report of Three Cases and Review of the Literature

Lipoma arborescens is a chronic, slow-growing, intra-articular lesion of benign nature, which is characterized by villous proliferation of the synovium, with replacement of the subsynovial connective tissue by mature fat cells. It usually involves the suprapatellar pouch of the knee joint. It is not a neoplasm but is rather considered a nonspecific reactive response to chronic synovial irritation, due to either mechanical or inflammatory insults. We report three cases of lipoma arborescens affecting the knee, the first in a young male without previous history of arthritis or trauma, the second in a 58-year-old male associated with osteoarthritis, and the final in a 44-year-old male diagnosed with psoriatic arthritis, which cover the entire pathologic spectrum of this unusual entity. We highlight the clinical findings and imaging features, by emphasizing especially the role of MRI, in the differential diagnosis of other, more complex intra-articular masses.

Cross-sectional and Longitudinal Associations between Knee Joint Effusion Synovitis and Knee Pain in Older Adults

Objective.To describe the cross-sectional and longitudinal associations between knee regional effusion synovitis and knee pain in older adults.Methods.Data from a population-based random sample (n = 880, mean age 62 yrs, 50% women) were used. Baseline knee joint effusion synovitis was graded (0–3) using T2-weighted magnetic resonance imaging (MRI) in the suprapatellar pouch, central portion, posterior femoral recess, and subpopliteal recess. Effusion synovitis of the whole joint was defined as a score of ≥ 2 in any subregion. Other knee structural (including cartilage, bone marrow, and menisci) lesions were assessed by MRI at baseline. Knee pain was assessed by the Western Ontario and McMaster Universities Osteoarthritis Index questionnaire at baseline and 2.6 years later. Multivariable analyses were performed after adjustment for age, sex, body mass index, and other structural lesions.Results.The prevalence of effusion synovitis was 67%. Suprapatellar pouch effusion synovitis was significantly and independently associated with increased total and nonweight-bearing knee pain in both cross-sectional and longitudinal analyses (for an increase in total knee pain of ≥ 5, RR 1.26 per grade, 95% CI 1.04–1.52), and increased weight-bearing knee pain in longitudinal analysis only. Effusion synovitis in posterior femoral recess and central portion were independently associated with increases in nonweight-bearing pain (RR 1.63 per grade, 95% CI 1.32–2.01 and RR 1.29 per grade, 95% CI 1.01–1.65, respectively) in longitudinal analyses only.Conclusion.Knee joint effusion synovitis has independent associations with knee pain in older adults. Suprapatellar pouch effusion synovitis is associated with nonweight-bearing and weight-bearing knee pain, while posterior femoral recess and central portion effusion synovitis are only associated with nonweight-bearing pain.

Association between MRI-detected knee joint regional effusion-synovitis and structural changes in older adults: a cohort study

ObjectiveTo describe the cross-sectional and longitudinal associations between knee regional effusion-synovitis and structural changes in older adults.MethodsA total of 977 subjects were randomly selected from the local community (mean 62 years, 50% female) at baseline and 404 were followed up 2.6 years later. T2-weighted MRI was used to assess knee effusion-synovitis in four subregions: suprapatellar pouch, central portion, posterior femoral recess and subpopliteal recess. Knee cartilage defects, cartilage volume and bone marrow lesions (BMLs) were measured using MRI at baseline and follow-up.ResultsCross-sectionally, effusion-synovitis in most subregions was significantly associated with a higher risk of cartilage defects, BMLs and reduced cartilage volume. Longitudinally, suprapatellar pouch effusion-synovitis at baseline predicted an increase in cartilage defects (p<0.01), loss of cartilage volume (p=0.04) and an increase in BMLs (p=0.02) in multivariable analyses. The significant associations of effusion-synovitis with cartilage volume and BMLs disappeared after adjustment for cartilage defects. Effusion-synovitis in whole knee joint (p<0.01) and subpopliteal recess (p<0.05) was consistently associated with longitudinal changes in cartilage defects but not in cartilage volume and BMLs.ConclusionsThere are independent associations between knee joint effusion-synovitis and knee cartilage defects in both cross-sectional and longitudinal analyses, suggesting a potential causal relationship. The associations of effusion-synovitis with BMLs and cartilage volume were largely dependent on cartilage defects, suggesting potential causal pathways.