Background There is emerging evidence that the development and progression of osteoarthritis (OA) is associated with inflammation. C reactive protein (CRP), a systemic marker for inflammation, may be elevated in OA patients but the evidence is conflicting. Objective To systematically review the literature for the relationship between serum CRP levels measured by a high sensitivity method (high sensitive CRP (hs-CRP)) and OA, as well as the correlation between circulating CRP levels and OA phenotypes. Methods MEDLINE, EMBASE and CINAHL databases were systematically searched from January 1992 to December 2012. Studies were included when they met the inclusion criteria and data from studies were extracted. Two independent reviewers assessed study quality using a modified Newcastle-Ottawa Quality Assessment Scale. Meta-analyses were performed to pool available data from included studies. Results 32 studies met the inclusion criteria. Serum hs-CRP levels in OA were modestly but statistically significantly higher than controls (mean difference=1.19 mg/L, 95% CI 0.64 to 1.73, p<0.001) with significant heterogeneity between studies. Levels were significantly associated with pain (r=0.14, 95% CI 0.09 to 0.20, p<0.001) and decreased physical function (r=0.25, 95% CI 0.13 to 0.39, p<0.001). No significant associations were found between hs-CRP levels and radiographic OA. Conclusions Low-grade systemic inflammation may play a greater role in symptoms rather than radiographic changes in OA.

Symptomatic knee osteoarthritis occurs among 10% of men and 13% of women aged 60 years or older.¹ Worldwide, knee osteoarthritis, together with hip osteoarthritis, are the 11th leading cause of global disability, accounting for 2.2% of total years lived with disability.² Medical costs of osteoarthritis account for 1% to 2.5% of the gross domestic product in developed countries.³ Currently there are no disease-modifying therapies for osteoarthritis; therefore, there is a need to develop cost-effective approaches to prevent the development and progression of osteoarthritis.

Background The infrapatellar fat pad (IPFP) is of uncertain significance for knee osteoarthritis. The aim of this study was to describe the longitudinal associations between baseline IPFP maximal area and changes in knee pain, knee cartilage volume and cartilage defects in older adults. Methods 356 community-dwelling male and female adults aged 50–80 years were measured at baseline and approximately 2.6 years later. T1-weighted or T2-weighted fat-suppressed MRI was used to assess maximal IPFP area, cartilage volume and cartilage defects at baseline and/or follow-up. Knee pain was assessed by the self-administered Western Ontario McMaster Osteoarthritis Index questionnaire. Results After adjustment for confounders, IPFP maximal area in women was significantly and negatively associated with changes in knee pain (β: −0.18 to −0.86 for total knee pain, pain at night while in bed, pain when sitting/lying and pain when standing upright, all p<0.05) but not with other knee pain subscales. IPFP maximal area in women was beneficially associated with change in tibial cartilage volume per annum (β: +1.56% per cm² at medial site; +0.86% per cm² at lateral site, both p<0.05), but not with change in patellar cartilage volume. Further, it was significantly associated with reduced risks of increases in medial cartilage defects (relative risk: 0·46 at tibial site, relative risk: 0.59 at femoral site; both p<0.05) but not with increases at other sites in women. No significant associations were found in men. Conclusions While the associations are not fully consistent, IPFP maximal area appears to have a protective role for knee symptoms and cartilage damage in older female adults.

Aims: The aim of this study was to estimate the 90-day periprosthetic joint infection (PJI) rates following total knee arthroplasty (TKA) and total hip arthroplasty (THA) for osteoarthritis (OA). Methods: This was a data linkage study using the New South Wales (NSW) Admitted Patient Data Collection (APDC) and the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR), which collect data from all public and private hospitals in NSW, Australia. Patients who underwent a TKA or THA for OA between 1 January 2002 and 31 December 2017 were included. The main outcome measures were 90-day incidence rates of hospital readmission for: revision arthroplasty for PJI as recorded in the AOANJRR; conservative definition of PJI, defined by T84.5, the PJI diagnosis code in the APDC; and extended definition of PJI, defined by the presence of either T84.5, or combinations of diagnosis and procedure code groups derived from recursive binary partitioning in the APDC. Results: The mean 90-day revision rate for infection was 0.1% (0.1% to 0.2%) for TKA and 0.3% (0.1% to 0.5%) for THA. The mean 90-day PJI rates defined by T84.5 were 1.3% (1.1% to 1.7%) for TKA and 1.1% (0.8% to 1.3%) for THA. The mean 90-day PJI rates using the extended definition were 1.9% (1.5% to 2.2%) and 1.5% (1.3% to 1.7%) following TKA and THA, respectively. Conclusion: When reporting the revision arthroplasty for infection, the AOANJRR substantially underestimates the rate of PJI at 90 days. Using combinations of infection codes and PJI-related surgical procedure codes in linked hospital administrative databases could be an alternative way to monitor PJI rates. Cite this article: Bone Joint J 2022;104-B(9):1060–1066.

Introduction: Recent studies regarding the infrapatellar fat pad (IPFP) mainly focus on the roles of the cells derived from the IPFP. There have been few clinical or epidemiological studies reporting on the association between the IPFP and knee osteoarthritis (OA). Our objective is to generate hypotheses regarding the associations between IPFP maximum area and knee OA measures in older adults. Methods: A total of 977 subjects between 50 and 80 years of age (mean, 62.4 years) participated in the study. Radiographic knee osteophyte and joint space narrowing (JSN) were assessed using the Osteoarthritis Research Society International atlas. T1- or T2-weighted fat suppressed magnetic resonance imaging (MRI) was utilized to assess IPFP maximum area, cartilage volume, cartilage defects, and bone marrow lesions (BMLs). Knee pain was assessed by self-administered Western Ontario McMaster Osteoarthritis Index (WOMAC) questionnaire. Results: After adjustment for potential confounders, IPFP maximum area was significantly associated with joint space narrowing (odds ratio (OR): 0.75, 95% confidence interval (CI): 0.62 to 0.91 (medial), 0.77, 95% CI: 0.62 to 0.96 (lateral)) and medial osteophytes (OR: 0.52, 95% CI: 0.35 to 0.76), knee tibial and patellar cartilage volume (β: 56.9 to 164.9 mm³/cm², all P <0.001), tibial cartilage defects (OR: 0.58, 95% CI: 0.41 to 0.81 (medial), 0.53, 95% CI: 0.40-0.71 (lateral)), any BMLs (OR: 0.77, 95% CI: 0.63 to 0.94), and knee pain on a flat surface (OR: 0.79, 95% CI: 0.63 to 0.98). IPFP maximum area was negatively, but not significantly, associated with femoral cartilage defects, lateral tibiofemoral BMLs, and total knee pain or other knee pain subscales. Conclusion: IPFP maximum area is beneficially associated with radiographic OA, MRI structural pathology and knee pain on a flat surface suggesting a protective role for IPFP possibly through shock absorption. Consequently, we must pay special attention to IPFP in the clinical settings, avoiding resection of normal IPFP in knee surgery.