Evaluation of loss of resistance technique using an air-filled injector to enhance accuracy of landmark-guided knee joint injections

Objectives: This study aims to compare the accurate intra-articular contrast distribution ratios between the loss of resistance with an airfilled injector (AFI) technique and the traditional landmark-guided knee injection in patients with knee osteoarthritis (OA). Patients and methods: Between July 2023 and December 2023, a total of 65 patients (8 males, 57 females; mean age: 65.6±8.3 years; range, 51 to 84 years) with Kellgren-Lawrence Stage 2-4 knee OA were randomly assigned to two groups as Group 1 (n=33) who were injected with a mixture of a contrast agent and triamcinolone hydrochloride and as Group 2 (n=32) who were injected with a 5-mL syringe containing 2 mL of air. After the air in the syringe was removed by loss of resistance, a mixture of contrast agent and triamcinolone hydrochloride was injected. Data including demographic and clinical characteristics of the patients were recorded. The contrast distribution was visualized by fluoroscopy in both groups. The patient's pain after the knee injection was evaluated using the Visual Analog Scale (VAS). Results: The groups were similar in terms of age, sex, body mass index, Kellgren-Lawrence stage, VAS score, duration of knee pain, and pain during knee injection (p>0.05). The accurate intra-articular contrast distribution ratios were 66.7% and 90.6% in Groups 1 and 2, respectively (p=0.019). No variable was found to be associated with an accurate intra-articular injection ratio. Conclusion: The AFI loss of resistance technique may significantly enhance the accuracy of landmark-guided knee injections and serve as a practical alternative in outpatient settings where imaging is unavailable.