Ultrasound revealing the synovial changes associated with knee osteoarthritis
Pathologically, osteoarthritis (OA) is marked by involvement of all joint tissues, mostly with focal cartilage loss, osteophyte formation, subchondral bone remodeling, and synovial and capsular thickening. As synovial hyperplasia in knees affected by OA is focal and less marked than in knees with rheumatoid arthritis, it may still play a crucial part in disease pathogenesis.
Studies have depicted a positive relation between synovial pathology and disease progression. Thus, now the question arises, whether synovitis is a potential biomarker of inflammatory response and therapeutic target in OA. A study was executed to find out the prevalence of synovial effusion, synovial hypertrophy and positive Doppler signal (DS) perceived by ultrasound (US) in people with knee OA and/or knee pain than in the general population.
In May 2015, a systematic literature search was undertaken in Medline, EMBASE, Allied and Complementary Medicine, PubMed Web of Science, and SCOPUS databases. The random effects model was used to detect the pooled frequencies of US abnormalities in people with knee OA/pain, in the general population or asymptomatic controls. Publication bias and heterogeneity between studies were investigated.
Total 24 studies in people with knee pain/OA and 5 studies of the general population or asymptomatic controls met the inclusion criteria. The pooled prevalence of US effusion, synovial hypertrophy and positive DS in people suffering from knee OA/pain were 51.5% (95% CI 40.2 to 62.8), 41.5% (26.3–57.5) and 32.7% (8.34–63.24), respectively, which were higher than those in the general population or asymptomatic controls (19.9% (95%CI 7.8–35.3%), 14.5% (0–58.81), and 15.8 (3.08–35.36), respectively). People with knee OA (ACR criteria or radiographic OA) had higher prevalence of US abnormalities than people with knee pain (P = 0.037, P = 0.010 and P = 0.009, respectively).
Thus, the US revealed effusion, synovial hypertrophy and DS are more frequent in people with knee OA/pain, compared to the general population. These abnormalities associate more to the occurrence of OA structural changes than to pain.