Degeneration of the acromioclavicular joint (AC) often causes impaired shoulder function and pain. Its infiltration results in reportedly beneficial short-term effects. Misplacement of infiltrations is observed in high numbers. A previous study showed high accuracy of infiltrations of one surgeon comparing conventional palpation technique to ultrasound guidance. This study evaluates if ultrasound-guided AC joint infiltration is feasible for therapists of different levels of experience and if the accuracy can be increased. One hundred and twenty AC joints of 60 cadavers were enrolled into a prospective, randomized observer-blinded study. Six therapists of three different levels of experience infiltrated 20 AC joints each. Half of them were infiltrated after palpation of the joint space, half of them were ultrasound-guided infiltrated. Controls were performed pre- and post-infiltration by an independent radiologist. In total, accurate infiltration was observed in 70%. In 25%, misplacement of the infiltration was recorded in the palpation-, in 2% in the ultrasound- and in 3% in both groups. The difference between the two groups was significant (P = 0.009). Ultrasound-guided infiltration to the AC joint is significantly more accurate than conventional palpation technique. This method is simple, efficient and can be applied by therapists of all levels of experience.