Background Musculoskeletal ultrasound (MSUS) has an increasingly important role in the evaluation and monitoring of knee arthritis, mainly because it is definitely more sensitive than clinical examination for detecting synovitis [1]. Although the method has been dramatically improved and refined in the last two decades, it can't occupy the right place in patient's medical management without a feasibility assessment.

Objectives To identify and analyse existing data regarding the feasibility of knee ultrasound (US) exam in clinical practice.

Methods A systematic literature search of PubMed and Web of Knowledge (Thomson Reuters), along with hand search of any available work or references not yet indexed, was performed using the terms: (“knee”) AND (“ultrasound” OR “ultrasonography”) AND (“feasibility” OR “pilot” OR “proof of concept”). The inclusion criteria consisted of feasibility studies regarding knee US or MSUS aided maneuver involving knee joint (unless including a surgical intervention) published during 2005–2015; non-adult based studies and those focused only on accuracy, reliability or validity, without considering the entire feasibility aspects, have been excluded. The selected papers were evaluated against a complex framework constructed around key areas mandatory for feasibility studies: acceptability, demand, implementation, practicality, adaptation, integration and expansion [2]. Aspects that might influence feasibility, such as machine characteristics, assessor's level of training and use of standardized scoring systems, were also considered.

Results One hundred fifty-two papers have been identified, of which 11 were finally selected for the review; 8 papers evaluated novel US scores, while the rest (3 articles) focused on evaluating US measurement of articular cartilage thickness by comparison with magnetic resonance imaging, US-guided intra-articular injections and incorporating MSUS in clinical practice, respectively. The total number of patients involved was 1172 – most of them (81.5%) suffering from rheumatoid arthritis (RA). Nine out of eleven studies quantified feasibility by the amount of time spent for the evaluation, without assessing any other aspects related to it; two discussed few more aspects: acceptability, implementation and practicality, but none of them practiced a systematic assessment of all feasibility areas.

Conclusions Although the knee is one of the most accessible joints with MSUS, the feasibility of this technique is poorly addressed. Almost all of the identified papers focus on a very limited aspect of feasibility (namely the amount of time needed to perform US) and on a very narrow pathology (patients with RA have been studied ten times more than those with osteoarthritis, despite the prevalence of these two diseases). This information gap should be properly addressed in next future works, in order to ensure the right place for MSUS technique.

1. Karim Z et al. Validation and reproducibility of ultrasonography in the detection of synovitis in the knee: a comparison with arthroscopy and clinical examination. Arthritis Rheum 2004;50(2):387–94.

2. Bowen D et al. How We Design Feasibility Studies. Am J Prev Med 2009;36(5):452–7

Disclosure of Interest None declared