Full mechanism, in text

Can knees go past toes in a squat?

1 · Klein 1961 — 60 years misread

The rule that knees must not pass the toes comes from a 1961 paper with unstandardised technique that others failed to replicate, yet textbooks spread it for 60 years.The rule knees can't go past toes has no real biomechanical basis; it originated in Klein 1961, an old paper — Klein reported the squat group had slightly looser knee ligaments than controls, and inferred squats hurt the knees.

Problems:
· Klein's study had no standardised squat technique; subjects did as they wished
· Multiple subsequent studies failed to replicate Klein's finding
· Klein himself retracted the recommendation in the 1970s
· But 1970s-1990s textbooks had already written knees past toes = knee injury into PE curricula, popular for 60 years

**Hartmann 2013 *Sports Med*, a literature review covering over 164 articles (not a ) and finally vindicated: full ROM progressively-loaded squats are safe and superior to partial squats for healthy knees**.

This is a classic case of marketing slogans travel 100× faster than scientific transmission.

2 · Force distribution — partial vs parallel vs ATG

A healthy squat shares load across hip, knee and ankle, while in a partial squat the hip barely participates and knee shear force is actually highest.Key concept: knees past toes isn't the problem; knees bearing load alone is. A healthy squat is synchronised hip-knee-ankle.

Partial / quarter squat (knee bent 30-60°):
· Knee shear force is actually highest — because the hip barely participates, all load on quadriceps + knee ligament
· Biceps femoris / gluteus maximus barely work
· Adaptation transfer is poor; in the long term it's pointless exercise

Parallel (90° knee bend):
· Hip-knee-ankle balanced loading
· Quadriceps + glutes + hamstrings + adductors all participate
· Powerlifter standard, the certified depth for international competition

ATG (Ass-To-Grass, full ROM, knee bend ≥ 120°):
· Quadriceps (especially VMO) activation maximum
· Gluteus maximus activation peak
· Hamstring co-activation ↑ → conversely protects the knee ligament
· Knees past toes is inevitable and normal (especially for tall people / shorter femurs)

Simple test: when squatting completely (ATG), if knees don't go past toes, you've most likely already fallen over — this is a biomechanical constraint, not a safety rule.

3 · Hartmann 2013 — vindication

With progressive loading and good technique, squat depth is not positively linked to knee injury risk; the real causes include valgus collapse and ramping volume too fast.**Hartmann 2013 *Sports Med*** is the most complete in this field, synthesising 200+ biomechanical + clinical studies.

Core conclusions:
· No positive correlation between squat depth and knee injury risk (under progressive loading + good technique)
· Full ROM squat stress on ligament / meniscus / cartilage ≤ partial / partial ROM squat
· Athlete training history: weightlifting / powerlifting athletes have lower knee injury rates than basketball / football / tennis
· Healthy knees can withstand thousands of full ROM squats — this is a structurally normal movement pattern

Counter-examples: what actually causes squat knee injuries
· Training volume progression > 10% / week — like running, this is #1
· Stiff posture — knee valgus collapse (knees caving inward) rather than past toes, is what actually hurts the knee
· Weak hip abductor / external rotator — weak link forces the knee to compensate
· Weight beyond capacity — ego lifting is a real cause
· No warm-up — cold start under heavy load

Knees past toes is the wrong scapegoat for these real causes.

4 · Practical — progressive ATG

Someone who never squats should progress to ATG over 12 weeks, from mobility to bodyweight to light load to barbell, stepping back a week at any pain.Ben Patrick (Knees Over Toes Guy) has helped many people rehabilitate over the past 5 years using ATG split squats + tibialis raises + sled drags — these end-range loaded trainings — an empirical counter to the mainstream.

But: jumping directly from never squatted to ATG squat is an injury breeding ground. Progressive 12-week protocol:

Weeks 1-3 · Mobility build-up:
· 90/90 hip external rotation stretch
· Squat sit (passive ATG 30s × 3)
· Lunge hip flexor stretch

Weeks 4-6 · Bodyweight progressive ATG:
· ATG bodyweight squat 8 reps × 3 sets
· ATG split squat (back leg elevated) 8 reps × 3
· If pain-free → continue, any pain → return to previous week

Weeks 7-9 · Add light load:
· Goblet squat to ATG, weight 10-20% body weight
· Focus is ROM, not load

Weeks 10-12 · Barbell ATG:
· Barbell front squat / back squat to ATG, 60-70%
· + 2.5-5 kg per week, don't rush

Red lines: any sharp / tearing / asymmetric pain → stop immediately + see a doctor. / dull pain: see recovery-science for management.

Full mechanism, in text

1 · Klein 1961 — 60 years misread

2 · Force distribution — partial vs parallel vs ATG

3 · Hartmann 2013 — vindication

4 · Practical — progressive ATG

Squat knee mechanics — 4 steps

Full mechanism, in text

1 · Klein 1961 — 60 years misread

2 · Force distribution — partial vs parallel vs ATG

3 · Hartmann 2013 — vindication

4 · Practical — progressive ATG

Squat knee mechanics — 4 steps