Ultrasonography findings in knee osteoarthritis: a prospective observational cross-sectional study of 100 patients.

Worldwide, knee osteoarthritis (KOA) accounts for 2.2% of total years lived with disability. There is a low correlation between joint tissue damage and pain intensity. Periarticular structures may be involved and cannot be identified in X-rays. To describe the main ultrasonography (USG) changes in symptomatic patients with primary KOA; to correlate the number of USG findings with KOA severity assessed by Kellgren and Lawrence (K&L) radiological scores, with pain intensity measured by a visual analogue scale (VAS) and with functioning scores assessed with the Timed up and go test (TUG) and Western Ontario and McMaster Universities (WOMAC) questionnaire. 100 patients with primary symptomatic KOA were assessed with X-ray and USG. Quantitative and qualitative analyses were evaluated in a systematic manner. The most frequent findings were joint effusion, pes anserinus bursitis, quadriceps tendon enthesopathy, popliteal cyst, iliotibial band tendinitis and patellar tendinitis. Pearson's correlation analysis demonstrated a significant moderate positive association between VAS scores and the number of USG findings (r = 0.36; p < 0.0001). The number of USG findings was different between K&L grades I and III (p = 0.041), I and IV (p < 0.001), and II and IV (p = 0.001, analysis of variance with Bonferroni correction). There was significant association between number of USG findings and TUG (r = 0.18; p = 0.014) and WOMAC scores for pain (r = 0.16; p < 0.029) and physical function domains (r = 0.16; p < 0.028). The most frequent USG finding was joint effusion. Periarticular structures should be explored as potential sources of pain and disability.