Quadriceps strength at three months tracked two-year scores after quadriceps tendon ACL reconstruction

Design

Single-centre retrospective case series

Population

100 patients after primary quadriceps tendon autograft ACL reconstruction

Primary outcome

IKDC and Lysholm scores at about 2 years

Effect

3-month isometric quadriceps symmetry: beta 3.9, adjusted R-squared 0.36 for IKDC

This single-centre case series followed 100 patients after primary ACL reconstruction with quadriceps tendon autograft, measuring limb symmetry indices for strength and function at three, six and nine months and patient-reported outcomes at about two years.

Quadriceps strength symmetry reached only 77-81% by nine months, while hamstring symmetry reached 98-100%. After adjustment for age, sex and BMI, isometric quadriceps symmetry at three months and fast isokinetic quadriceps symmetry at nine months were associated with higher IKDC and Lysholm scores. Patients who reached an acceptable symptom state generally had 60-70% quadriceps symmetry by three months.

This is a case series without a comparison group, so it shows association, not that pushing quadriceps work changes outcomes. But it fits the clinical experience that quadriceps tendon harvest leaves a lasting quadriceps deficit, and that early strength is a useful marker of who is on track.

• Measure quadriceps strength symmetry at about three months after quadriceps tendon ACL reconstruction.
• Consider intensifying quadriceps rehabilitation when symmetry is well below 60-70% at that point.
• Expect quadriceps symmetry to lag hamstring symmetry after this graft.
• Use objective strength testing, not time alone, when judging readiness to return to sport.

Why it matters

It gives rehabilitation teams an early checkpoint rather than waiting until return-to-sport testing.

Don't overread it

This is a 100-patient case series; it cannot show that improving early strength improves later outcomes.

The statistics, in plain English

An adjusted R-squared of 0.36 means early quadriceps symmetry explained about a third of the variation in two-year knee scores, which is substantial for a single measure but leaves most of the variation unexplained.

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