The ABC of fluid-filled structures around the knee
Dr John Ferrier, York and Scarborough Teaching Hospitals NHS Foundation Trust
Aim
Fluid-filled structures present clinically as non-specific soft tissue lumps. The low cost and lack of ionising radiation offered by ultrasound makes it the first line of investigation for this presentation. Fluid-filled structures have defined ultrasound characteristics and therefore can be similar in appearance. As such, differentiating the spectrum of fluid-filled structures around a certain joint can be difficult, but is crucial for guiding clinicians and reassuring patients. We aim to outline the differing ultrasound appearances of fluid-filled structures around the knee, with reference to their clinical presentations and expected anatomical locations.
Methods
By presenting cases from our own practice, some with cross-sectional correlation, we outline the anatomical knowledge which contributes to determining the nature and origin of a variety of fluid-filled structures adjacent to the knee joint. This case-based approach allows us to share our experience of creating a differential diagnosis and supporting management of periarticular lesions.
Results
Cases include periarticular bursae and cysts, the knee joint articulation itself as well as its common recesses and outpouchings. We will also cover more complex and rare lesions, which may need further investigation.
Conclusion
Fluid-filled structures are common around the knee; they can appear identical on imaging. With reference to a series of cases, we outline the anatomical and clinical considerations which contribute to differentiating these structures on ultrasound.