Joint compression alters the kinematics and loading patterns of the intact and capsule-transected AC joint

High compressive loads are transmitted through the shoulder across the acromioclavicular (AC) joint to the axial skeleton during activities of daily living and can lead to early joint degeneration or instability. The objective of this study was to quantify the effect of joint compression on the biomechanics of the intact and capsule-transected AC joint during application of three loading conditions. A robotic/universal force–moment sensor testing system was utilized to apply an anterior, posterior or superior load of 70 N in combination with 10 or 70 N of joint compression to fresh-frozen cadaveric shoulders ( n=12). The application of joint compression to the intact AC joint decreased the posterior translation in response to a posterior load (−6.6±2.5 vs −3.7±1.0 mm, p