Dunning and colleagues tested whether muscle activity and forearm position stabilize the elbow after the lateral collateral ligament is divided.
Simulator study of 10 cadaver arms (mean age 79) moved through cables on five tendons, tested intact and after the capsule and lateral collateral ligament were divided at the epicondyle.
Muscle activity stabilizes the elbow, and forearm pronation reduces posterolateral rotatory instability.
Key Findings
With the arm vertical during passive flexion, the ligament‑deficient elbow was as stable as intact with the forearm pronated. With the forearm supinated, rotatory instability increased significantly.
Simulated active flexion reduced that instability. With the forearm supinated, the deficient elbow then differed from intact only at 120° of flexion.
In varus and valgus orientations, dividing the ligament increased laxity in both forearm positions. Pronation was more stable than supination, but the elbow remained grossly unstable either way.
In the varus orientation, ligament‑deficient elbows dislocated whenever active flexion was attempted, so it could not be tested.
The authors propose that the elbow flexors and triceps compress the joint surfaces, which may explain why patients often have few symptoms during normal activities.
The extensor origin and anconeus were not reattached anatomically, so their stabilizing role could not be tested. The authors call for clinical studies to confirm the findings.
Authors' conclusion
The stabilizing effect of muscle activity suggests physical therapy of the lateral collateral ligament deficient elbow should focus on active rather than passive mobilization, while avoiding shoulder abduction to minimize varus elbow stress. Passive mobilization should be done with the forearm maintained in pronation.
Dunning and colleagues tested whether muscle activity and forearm position stabilize the elbow after the lateral collateral ligament is divided.
Simulator study of 10 cadaver arms (mean age 79) moved through cables on five tendons, tested intact and after the capsule and lateral collateral ligament were divided at the epicondyle.
Muscle activity stabilizes the elbow, and forearm pronation reduces posterolateral rotatory instability.
Key Findings
With the arm vertical during passive flexion, the ligament‑deficient elbow was as stable as intact with the forearm pronated. With the forearm supinated, rotatory instability increased significantly.
Simulated active flexion reduced that instability. With the forearm supinated, the deficient elbow then differed from intact only at 120° of flexion.
In varus and valgus orientations, dividing the ligament increased laxity in both forearm positions. Pronation was more stable than supination, but the elbow remained grossly unstable either way.
In the varus orientation, ligament‑deficient elbows dislocated whenever active flexion was attempted, so it could not be tested.
The authors propose that the elbow flexors and triceps compress the joint surfaces, which may explain why patients often have few symptoms during normal activities.
The extensor origin and anconeus were not reattached anatomically, so their stabilizing role could not be tested. The authors call for clinical studies to confirm the findings.
Authors' conclusion
The stabilizing effect of muscle activity suggests physical therapy of the lateral collateral ligament deficient elbow should focus on active rather than passive mobilization, while avoiding shoulder abduction to minimize varus elbow stress. Passive mobilization should be done with the forearm maintained in pronation.