Comparison of ultrasound (US)-guided intra-articular injections by in-plain and out-of-plain on medial portal of the knee

To compare the accuracy rates between ultrasound (US)-guided in-plain (IP), out-of-plain (OOP) and blind knee intra-articular (IA) injection via the mid-medial portal. US-guided IA injection in the IP, OOP, and blind methods was performed on 126 knees with radiographically confirmed knee osteoarthritis (Kellgren-Lawrence grade 2 or 3) without effusion. About 6 ml of a mixed material containing 1 % lidocaine (1 mL) and triamcinolone 20 mg (1 mL) and nonionic contrast (4 mL) was injected into the IA space of the knee through the mid-medial portals. After an US-guided and blind IA injection into the knee joint, a radiographic image was taken to determine whether the injected material had reached the IA space or infiltrated into the soft tissue. US-guided IA injections in the IP (97 %; P < 0.05) and OOP method (95 %; P < 0.05) showed significantly higher accuracy rate than injections in the blind injection (78 %). Both US-guided IA injection methods may be used to access the knee joint with high degree of accuracy.