Objectives
To understand the diagnostic utility of ultrasound (US) for early diagnosis of knee osteoarthritis (KOA), this study aims to assess the frequency of KOA-associated US-detectable synovitis, osteophytes, and meniscal extrusion and their mutual association in patients diagnosed with recent-onset symptomatic KOA.

Methods
The study included 476 patients (median age: 61) diagnosed with unilateral KOA in a recent-onset symptomatic (<2 years of pain) stage. All patients underwent an US exam assessing the presence of synovitis, osteophytes (lateral, medial, trochlear) and meniscus extrusion (medial, lateral), dichotomized as present or absent. A multivariate logistic regression analysis was performed to assess their mutual association.

Results
The frequency of synovitis, osteophytes, and meniscal extrusion on US was 82.8 %, 87.0 %, and 44.7 %, respectively. At least one feature was detected in 97.7 % of the knees. All three features together were found in 32.6 % of the knees. In 73.1 % of the knees both synovitis and osteophytes were observed (odds ratio [OR] = 1.81, 95 % CI 0.95–3.45) and 37.8 % of the knees displayed meniscal extrusion along with synovitis (OR = 1.19, 95 % CI 0.73–1.94). Medial osteophytes alongside medial meniscal extrusion was identified in 30.5 % of the knees (OR = 1.26, 95 % CI 0.76–2.08), while lateral osteophytes alongside lateral extrusion was observed in 8.4 % of the knees (OR = 6.50, 95 % CI 3.31–12.77).

Conclusions
Nearly all recent-onset symptomatic osteoarthritic knees exhibit at least one US-detectable KOA-associated feature. This underlines that even in KOA patients with short duration of pain, significant changes are already evident on US, offering potential support for earlier intervention and more targeted management strategies.