Glenohumeral joint laxity and stiffness in the functional throwing position of high school baseball pitchers.

CONTEXT

Repetitive overhead throwing has been theorized to result in chronic adaptations to the capsuloligamentous restraints of the glenohumeral joint.

OBJECTIVE

To compare glenohumeral joint laxity and stiffness between the throwing and nonthrowing shoulders of high school baseball pitchers.

DESIGN

Repeated measures.

SETTING

High school athletic training facilities.

PATIENTS OR OTHER PARTICIPANTS

Twenty-two asymptomatic high school baseball pitchers (age = 16.50 +/- 0.74 years, height = 178.51 +/- 7.66 cm, mass = 75.43 +/- 13.24 kg) from a sample of convenience.

MAIN OUTCOMES MEASURE(S): We used computerized stress arthrometry to measure glenohumeral joint laxity and stiffness. Anterior glenohumeral joint laxity and stiffness measures were obtained with the shoulder in 90 degrees of abduction and both neutral rotation and 90 degrees of external rotation. Posterior laxity and stiffness measures were obtained with the shoulder in 90 degrees of abduction and neutral rotation.

RESULTS

No clinically significant differences were found for glenohumeral laxity or stiffness between sides. However, a statistically significant main effect for position was present for both laxity and stiffness. Anterior glenohumeral joint laxity in the 90 degrees external rotation position was significantly decreased and stiffness was increased in this position compared with the anterior at neutral and posterior at neutral positions.

CONCLUSIONS

Glenohumeral joint laxity decreases and stiffness increases in the functional throwing position of 90 degrees of abduction and 90 degrees of external rotation. No clinically significant side-to-side differences or directional differences were found in high school baseball pitchers.