Knee Biomechanics of the Dynamic Squat Exercise: Shear and Compressive Forces
Escamilla RF
Evidence is still building up
Summary
A review synthesizing biomechanics research on shear force, compressive force, and muscle activity at the knee during the squat. Posterior shear force, restrained mainly by the posterior cruciate ligament (PCL), remains low to moderate across the full range of knee flexion. Anterior shear force (restrained by the ACL) is generated only in the shallow 0–60° range. Patellofemoral compressive force and tibiofemoral compressive and shear force, in contrast, progressively increase with deeper knee flexion, peaking near maximum flexion. Citing this increase in compressive load, the author recommends the parallel squat over the deep squat for athletes with healthy knees, and concludes that injury potential to the menisci, cruciate ligaments, and collateral ligaments may increase with the deep squat.
Key findings
- 1
Posterior shear force stays low to moderate across all knee flexion angles, restrained primarily by the PCL
- 2
Anterior shear force (restrained by the ACL) occurs only in the shallow 0–60° range — deep squats themselves do not increase ACL loading
- 3
Patellofemoral compressive force and tibiofemoral compressive and shear force increase progressively with deeper flexion, peaking near maximum flexion (this is compressive *force*; a separate review, squat-depth-knee-load-review, notes that compressive *stress* on the joint surface may be redistributed at depth via the wrapping effect)
- 4
Citing this increase in compressive load, the review recommends the parallel squat over the deep squat for athletes with healthy knees
- 5
It concludes that injury potential to the menisci, cruciate ligaments, and collateral ligaments may increase with the deep squat
- 6
A low-bar position tends to reduce knee compressive forces and may be preferable for those with a history of knee issues
Related research
Squat Depth and Load on the Knee and Spine: A Review of 164 Studies
Sports Medicine, 2013
A review integrating 164 studies on how squat depth relates to knee and spine loading. Assuming healthy knees and proper form, there is no evidence that deep squats increase injury risk; heavy partial squats with supramaximal loads may instead promote long-term degeneration.
Deep vs Shallow Squats for Hypertrophy and Strength: A 12-Week RCT
European Journal of Applied Physiology, 2013
A 12-week RCT in 17 healthy young men comparing high-load squats through a deep (0–120°) versus shallow (0–60°) range of motion. The deep group showed superior anterior thigh hypertrophy, knee-extension strength and jump performance.
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