Accuracy of ultrasound-guided knee injections confirmed by fluoroscopy

Background: Injection with viscosupplements is a common treatment for knee osteoarthritis. However, there is a lack of knowledge about how the injectate spreads within the knee following an injection. Objective: Using ultrasound and fluoroscopy, this study seeks to assess whether injectate introduced into the suprapatellar recess disperses into the tibiofemoral joint. Design: Descriptive case series and reliability test-retest study. Setting: Outpatient rehabilitation center at an academic teaching hospital. Patients: 14 adults between 44 and 80 with knee osteoarthritis, defined as a grade 2–4 on the Kellgren and Lawrence scale, who were candidates for hyaluronic acid injections. Interventions: Participants received ultrasound guided knee injections into the suprapatellar recess with hyaluronic acid and contrast. Post-injection fluoroscopic images were taken. The participants then underwent a walking protocol. Post-walking fluoroscopic images were then taken. Main outcome measurements: Determining if an injectate introduced into suprapatellar recess localizes to the tibiofemoral joint following a walking test; and assessing interrater agreement with between 2 radiologists and 1 interventional physiatrist with regards to location of injectate. Results: Injectate placed in the suprapatellar recess using ultrasound-guided technique will disperse to a varying extent from the suprapatellar recess into the tibiofemoral or patellofemoral joint after a brief bout of walking. Images of US-guided knee injections identified by an experienced interventionalist to represent correct needle placement and injectate location, confirmed by reference-standard fluoroscopy, can be corroborated by a blinded radiologist and are therefore reliable. Conclusions: Fluoroscopic imaging confirmed that ultrasound-guided injection of hyaluronic acid into the suprapatellar recess dispersed into the tibiofemoral joint after a walking test. Future studies should examine whether the amount of injectate found in the tibiofemoral joint is correlated with patient outcomes. Level of evidence: Level IV.