Impact of hamstring versus quadriceps tendon graft on thigh muscle strength and surface electromyography activity after anterior cruciate ligament reconstruction

Abstract Purpose To compare quadriceps tendon (QT) and hamstring tendon (HT) autografts regarding isometric thigh muscle strength, surface electromyography (sEMG) activity and clinical outcomes following anterior cruciate ligament reconstruction (ACLR). Methods Sixty patients (HT: n = 36; QT: n = 24) were evaluated at a mean follow‐up of 24 months. Maximum isometric strength of knee flexors and extensors was measured and normalised to body weight. Muscle activity of the quadriceps and hamstrings was evaluated using sEMG and normalised to maximum voluntary contraction (MVC). Clinical assessments included the Lachman, Pivot‐Shift and Rolimeter tests, as well as patient‐reported outcome measures (International Knee Documentation Committee, Lysholm, Tegner activity scale). Results Limb symmetry index (LSI) values did not differ significantly between the HT and QT group. Within‐group analysis showed reduced flexion strength in the HT group ( p < 0.001) and reduced extension strength in the QT group ( p = 0.045). The HT group demonstrated significantly lower bodyweight‐normalised flexion strength compared to the QT group ( p = 0.034), with no difference in extension strength ( p = 0.184). No significant differences were observed in sEMG activity between graft types or limb sides. Clinical stability and patient‐reported outcomes did not differ between groups. Conclusion Both grafts provide excellent clinical outcomes. No statistically significant differences in muscle activation were detected at midterm follow‐up, yet equivalence should not be inferred from this finding. This is one of the first studies to include sEMG analysis during maximum isometric contractions when comparing QT and HT grafts. Persistent graft‐specific weaknesses, quadriceps after QT and hamstrings after HT, highlight the need for targeted rehabilitation focusing on the affected muscle group to address these imbalances. Level of Evidence Level III.