Tibial Internal Rotation Contributes to Knee Stability During Terminal Knee Extension
During terminal knee extension in closed-chain squatting exercises, tibial internal rotation is the primary bony movement that contributes to knee stability. This biomechanical phenomenon is critical for maintaining joint integrity during weight-bearing activities.
Biomechanics of Terminal Knee Extension
- In closed kinetic chain exercises like squats, terminal knee extension (the final 15-20° of extension) involves a specific sequence of bony movements that enhance joint stability 1
- As the knee approaches full extension during the concentric phase of a squat, the tibia internally rotates relative to the femur, creating what is known as the "screw-home mechanism" 1, 2
- This internal rotation of the tibia during terminal extension increases congruency between articular surfaces and tightens the anterior cruciate ligament (ACL), providing enhanced stability in the fully extended position 1
Stability Mechanisms During Closed Chain Exercises
- Closed kinetic chain exercises like squats produce significantly less posterior shear force at the tibiofemoral joint compared to open kinetic chain exercises, contributing to better joint stability 3
- During terminal extension in weight-bearing positions, the internal rotation of the tibia locks the knee joint, creating a more stable position for weight-bearing 2
- This rotational movement is coupled with increased muscular co-contraction, particularly of the quadriceps and gastrocnemius muscles, which further enhances knee stability 4
Clinical Significance
- Understanding the role of tibial internal rotation during terminal knee extension is crucial for rehabilitation protocols following knee injuries or surgeries 5
- Closed kinetic chain exercises are generally recommended over open kinetic chain exercises for knee rehabilitation due to their ability to minimize sagittal translation and enhance stability 4
- Both open and closed kinetic chain exercises are recommended for regaining quadriceps strength post-injury, but closed chain exercises may provide better joint stability during the rehabilitation process 5
Patellofemoral Considerations
- The screw-home mechanism involving tibial internal rotation during terminal extension helps optimize patellofemoral tracking and reduces anterior knee pain 5
- Patients with better patient-reported outcomes after total knee arthroplasty demonstrate more stable medial compartment kinematics during closed chain exercises, highlighting the importance of proper rotational mechanics 6
- Open kinetic chain exercises might induce more anterior knee pain compared to closed kinetic chain exercises, possibly due to differences in tibiofemoral kinematics and the absence of the natural screw-home mechanism 5
Common Pitfalls and Considerations
- Failure to achieve proper tibial internal rotation during terminal extension may lead to knee instability and increased risk of injury 1
- Excessive focus on open kinetic chain exercises without incorporating closed chain movements may not adequately train the natural stabilizing mechanisms of the knee 7
- Rehabilitation protocols should incorporate exercises that promote proper tibial rotation patterns to restore normal knee biomechanics 7
Understanding the role of tibial internal rotation during terminal knee extension provides valuable insights for designing effective rehabilitation and training programs that enhance knee stability and function during weight-bearing activities.