The pes anserinus (PA) is the conjoint tendon of the sartorius, gracilis, and semitendinosus muscles, inserting onto the proximal anteromedial tibia approximately 5 cm distal to the medial tibial joint line. Deep to the PA tendon the PA bursa (PAB) is located, which serves to reduce friction between the superficially located PA tendon and the structures that lie deep to it, including the medial tibia and the medial collateral ligament.
The purpose of a study done by Lee et al. (2018) was to evaluate the accuracy of ultrasound (US) guided PAB injections, and to assess the clinical outcomes of the effects of injection accuracy by comparing them to blind injections
Both US-guided and blind PAB injections significantly reduced short term pain intensity. Accuracy was greater in the US-guided injection group than in the blind injection group, and clinical outcomes were more greatly affected in the US group. After the US-guided injections, all injectates were located in the PAB, while only a small amount of the blind injections' injectates were located in the PAB.