This 1983 cadaveric study from Morrey and An at Mayo Clinic was the first to quantify how the MCL, RCL, anterior capsule, and bony articulation each resist valgus, varus, and distraction loads at the elbow. Four specimens were tested in full extension and at 90° of flexion using a constant-displacement ligament-sectioning technique. The paper established the MCL as the primary soft tissue stabilizer and laid the biomechanical groundwork for UCL reconstruction in the throwing athlete.
Before this paper, recurrent elbow dislocation was often treated with bone block procedures or lateral (radial collateral) ligament reconstruction — targeting structures this study showed are minor stabilizers. Morrey and An's data provided the first quantitative evidence that the MCL (anterior band of the UCL) is the keystone stabilizer, setting the stage for UCL reconstruction in throwing athletes.
When you evaluate a pitcher with medial elbow pain and valgus instability, this is the paper behind your reasoning: at 90° of flexion (the position of late cocking and acceleration), the MCL carries ~55% of valgus load and 78% of distraction load. The capsule contributes almost nothing in flexion. So capsular laxity will not be bailed out by other soft tissue structures at that position.
For varus instability, trust the joint itself before the RCL: at 90° of flexion, 75% of varus resistance comes from bony articulation. A patient with persistent varus instability after ligament repair likely has articular cartilage loss or coronoid/radial head deficiency driving the problem.
The anterior capsule's clinical legacy is contracture, not instability. Its fibrotic healing after elbow injury is the biomechanical basis for post-traumatic elbow stiffness.
This 1983 cadaveric study from Morrey and An at Mayo Clinic was the first to quantify how the MCL, RCL, anterior capsule, and bony articulation each resist valgus, varus, and distraction loads at the elbow. Four specimens were tested in full extension and at 90° of flexion using a constant-displacement ligament-sectioning technique. The paper established the MCL as the primary soft tissue stabilizer and laid the biomechanical groundwork for UCL reconstruction in the throwing athlete.
Before this paper, recurrent elbow dislocation was often treated with bone block procedures or lateral (radial collateral) ligament reconstruction — targeting structures this study showed are minor stabilizers. Morrey and An's data provided the first quantitative evidence that the MCL (anterior band of the UCL) is the keystone stabilizer, setting the stage for UCL reconstruction in throwing athletes.
When you evaluate a pitcher with medial elbow pain and valgus instability, this is the paper behind your reasoning: at 90° of flexion (the position of late cocking and acceleration), the MCL carries ~55% of valgus load and 78% of distraction load. The capsule contributes almost nothing in flexion. So capsular laxity will not be bailed out by other soft tissue structures at that position.
For varus instability, trust the joint itself before the RCL: at 90° of flexion, 75% of varus resistance comes from bony articulation. A patient with persistent varus instability after ligament repair likely has articular cartilage loss or coronoid/radial head deficiency driving the problem.
The anterior capsule's clinical legacy is contracture, not instability. Its fibrotic healing after elbow injury is the biomechanical basis for post-traumatic elbow stiffness.