Knee hyperextension does not adversely affect dynamic in vivo kinematics after anterior cruciate ligament reconstruction

Knee Surg Sports Traumatol Arthrosc. 2018 Feb;26(2):448-454. doi: 10.1007/s00167-017-4653-0. Epub 2017 Jul 15.


Purpose: To evaluate the effect of knee hyperextension on dynamic in vivo kinematics after anterior cruciate ligament reconstruction (ACL-R).

Methods: Forty-two patients underwent unilateral ACL-R. Twenty-four months after surgery, subjects performed level walking and downhill running on a treadmill while dynamic stereo radiographs were acquired at 100 (walking) and 150 Hz (running). Tibiofemoral motion was determined using a validated model-based tracking process, and tibiofemoral translations/rotations were calculated. The range of tibiofemoral motions from 0 to 10% of the gait cycle (heel strike to early stance phase) and side-to-side difference (SSD) were calculated. Maximum knee extension angle of ACL-reconstructed knees during walking was defined as active knee extension angle in each subject. Correlations between maximum knee extension angle and tibiofemoral kinematics data were evaluated using Spearman's rho (P < 0.05).

Results: No significant correlation was observed between maximum knee extension angle and the range of anterior tibial translation during functional activities in the ACL-R knees. Maximum knee extension angle was weakly correlated with internal tibial rotation range in ACL-R knee during running (ρ = 0.376, P = 0.014); however, maximum extension angle was not correlated with SSD of internal tibial rotation. SSD of internal tibial rotation was -0.4° ± 1.9° (walking), -1.6° ± 3.1° (running), indicating ACL-R restored rotatory knee range of motion during functional movements.

Conclusion: Knee hyperextension was not significantly correlated with greater SSD of anterior translation and internal rotation. The clinical relevance is that knee hyperextension does not adversely affect kinematic outcomes after ACL-R and that physiologic knee hyperextension can be restored after ACL-R when knee hyperextension is present.

Level of evidence: III.

Keywords: ACL; Anterior cruciate ligament reconstruction; Dynamic stereo X-ray system; Hyperextension; Kinematics; Knee.

Publication types

  • Comparative Study
  • Randomized Controlled Trial

MeSH terms

  • Adolescent
  • Adult
  • Anterior Cruciate Ligament Injuries / physiopathology*
  • Anterior Cruciate Ligament Injuries / surgery
  • Anterior Cruciate Ligament Reconstruction* / methods
  • Biomechanical Phenomena
  • Exercise Test
  • Female
  • Femur / physiopathology
  • Femur / surgery
  • Gait / physiology
  • Humans
  • Knee Joint / physiopathology*
  • Knee Joint / surgery
  • Male
  • Range of Motion, Articular / physiology*
  • Rotation
  • Running / physiology
  • Tibia / physiopathology
  • Tibia / surgery
  • Walking / physiology
  • Young Adult