Evaluation of the Gliding of Posterior Elbow Fat Pad Using Ultrasonography and Particle Image Velocimetry.

Background: Previous studies have utilized ultrasonography (US) to dynamically evaluate Kager's and infrapatellar fat pads. However, limited research has focused on the dynamic assessment of the posterior fat pad of the elbow joint, and its correlation with elbow pain remains unclear. Therefore, this study aimed to investigate the gliding of the posterior elbow fat pad in healthy patients using US. Methods: US was performed on 40 healthy patients. The patients were placed in a sitting position with the upper limb on the bed; they performed an automatic movement from 90° flexion to full extension of the elbow joint for 2 s following a fixed rhythm using a digital timer. Moving images of the fat pad gliding were analyzed for the direction of movement and gliding velocity using particle image velocimetry. Statistical analyses were performed using Friedman test. Results: The posterior fat pad glided into the olecranon fossa within the range of 0%-50% elbow extension. At 50% extension, the posterior fat pad showed a proximal posterior direction of movement. A significant increase in sliding velocity was observed from 0% to 50% extension ( Conclusion: Our results indicate that the velocity and direction of gliding of the fat pad behind the elbow joint in healthy patients vary with changes in the elbow joint extension angle. US proves to be a valuable tool for evaluating the posterior elbow fat pad.