Knee Kinetics in Baseball Hitting and Return to Play after ACL Reconstruction

Area of Science:

• Sports Medicine
• Biomechanics
• Orthopedics

Background:

• Anterior Cruciate Ligament (ACL) reconstruction requires a structured return-to-sport protocol.
• Baseball hitting imposes unique kinetic demands on the knee joint.

Purpose of the Study:

• To quantify knee kinetics during baseball tee hitting.
• To develop a predictive model for knee kinetics using accessible measures.
• To establish a timeline for resuming hitting post-ACL reconstruction.

Main Methods:

• Nineteen high school baseball athletes performed tee hitting.
• Knee kinetics were measured using an electromagnetic tracking system.
• Linear regression models predicted knee torques and forces from anthropometric data and exit velocity.

Main Results:

• Predictive models successfully estimated front knee net, internal/external rotation, extension, varus torque, and anterior force.
• Back knee net and valgus torque were also predicted.
• Knee kinetics were compared to rehabilitation exercises to inform return-to-play timelines.

Conclusions:

• Tee hitting may be initiated 13 weeks post-ACL reconstruction if the front knee is involved.
• Tee hitting may be initiated 17 weeks post-ACL reconstruction if the back knee is involved.
• This study provides evidence-based guidelines for the safe return to baseball hitting after ACL reconstruction.