Background: The anterior cruciate ligament (ACL) has been well defined as the main passive restraint to anterior tibial translation (ATT) in the knee and plays an important role in rotational stability. However, it is unknown how closely the ACL and other passive and active structures of the knee constrain translations and rotations across a set of functional activities of increasing demand on the quadriceps.
Hypothesis: Anterior tibial translation and internal rotation of the tibia relative to the femur would increase as the demand on the quadriceps increased.
Study Design: Controlled laboratory study.
Methods: The in vivo 3-dimensional knee kinematics of 10 adult female patients (height, 167.8 ± 7.1 cm; body mass, 57 ± 4 kg; body mass index [BMI], 24.8 ± 1.7 kg/m2; age, 29.7 ± 7.9 years) was measured using biplane fluoroscopy while patients completed 4 functional tasks. The tasks included an unloaded knee extension in which the patient slowly extended the knee from 90° to 0° of flexion in 2 seconds; walking at a constant pace of 90 steps per minute; a maximum effort isometric knee extension with the knee at 70° of flexion; and landing from a height of 40 cm in which the patient stepped off a box, landed, and immediately performed a maximum effort vertical jump.
Results: Landing (5.6 ± 1.9 mm) produced significantly greater peak ATT than walking (3.1 ± 2.2 mm) and unweighted full extension (2.6 ± 2.1 mm) (P < .01), but there was no difference between landing and a maximum isometric contraction (5.0 ± 1.9 mm). While there was no significant difference in peak internal rotation between landing (19.4° ± 5.7°), maximum isometric contraction (15.9° ± 6.7°), and unweighted full knee extension (14.5° ± 7.7°), each produced significantly greater internal rotation than walking (3.9° ± 4.2°) (P < .001). Knee extension torque significantly increased for each task (P < .01): unweighted knee extension (4.7 ± 1.2 N·m), walking (36.5 ± 7.9 N·m), maximum isometric knee extension (105.1 ± 8.2 N·m), and landing (140.2 ± 26.2 N·m).
Conclusion: Anterior tibial translations significantly increased as demand on the quadriceps and external loading increased. Internal rotation was not significantly different between landing, isometric contraction, and unweighted knee extension. Additionally, ATT and internal rotation from each motion were within the normal range, and no excessive amounts of translation or rotation were observed.
Clinical Relevance: This study demonstrated that while ATT will increase as demand on the quadriceps and external loading increases, the knee is able to effectively constrain ATT and internal rotation. This suggests that the healthy knee has a safe envelope of function that is tightly controlled even though task demand is elevated.
Background: Bone bruises located on the lateral femoral condyle and posterolateral tibia are commonly associated with anterior cruciate ligament (ACL) injuries and may contribute to the high risk for knee osteoarthritis after ACL injury. The resultant footprint (location) of a bone bruise after ACL injury provides evidence of the inciting injury mechanism.
Purpose/Hypothesis: (1) To analyze tibial and femoral articular cartilage pressure distributions during normal landing and injury simulations, and (2) to evaluate ACL strains for conditions that lead to articular cartilage pressure distributions similar to bone bruise patterns associated with ACL injury. The hypothesis was that combined knee abduction and anterior tibial translation injury simulations would demonstrate peak articular cartilage pressure distributions in the lateral femoral condyle and posterolateral tibia. The corollary hypothesis was that combined knee abduction and anterior tibial translation injury conditions would result in the highest ACL strains.
Study Design: Descriptive laboratory study.
Methods: Prospective biomechanical data from athletes who subsequently suffered ACL injuries after testing (n = 9) and uninjured teammates (n = 390) were used as baseline input data for finite element model comparisons.
Results: Peak articular pressures that occurred on the posterolateral tibia and lateral femoral condyle were demonstrated for injury conditions that had a baseline knee abduction angle of 5°. Combined planar injury conditions of abduction/anterior tibial translation, anterior tibial translation/internal tibial rotation, or anterior tibial translation/external tibial rotation or isolated anterior tibial translation, external tibial rotation, or internal tibial rotation resulted in peak pressures in the posterolateral tibia and lateral femur. The highest ACL strains occurred during the combined abduction/anterior tibial translation condition in the group that had a baseline knee abduction angle of 5°.
Conclusion: The results of this study support a valgus collapse as the major ACL injury mechanism that results from tibial abduction rotations combined with anterior tibial translation or external or internal tibial rotations.
Clinical Relevance: Reduction of large multiplanar knee motions that include abduction, anterior translation, and internal/external tibial motions may reduce the risk for ACL injuries and associated bone bruises. In particular, prevention of an abduction knee posture during initial contact of the foot with the ground may help prevent ACL injury.
Background: Female athletes are at a greater risk for noncontact anterior cruciate ligament injuries than male athletes. Gender differences in frontal plane kinematics (hip adduction, knee valgus, and ankle eversion) and temporal relationships that make up the components of dynamic knee valgus may explain this discrepancy.
Hypothesis: The authors hypothesized that women would reach peak frontal plane kinematic values earlier during landing compared with their male counterparts.
Study Design: Controlled laboratory study.
Methods: Hip, knee, and ankle 3-dimensional kinematics were measured using high-speed motion capture in 10 National Collegiate Athletic Association Division I female athletes and 10 male practice squad athletes during a drop-jump landing. Independent t tests were used to analyze each dependent variable to identify differences between genders.
Results: Maximum hip adduction, knee valgus, and ankle eversion occurred earlier in women than in men (mean differences 33.7% of stance [95% CI, 20.2%-47.2%], 41.7% [95% CI, 31.5%-51.6%], 16.5% of stance [95% CI, 7.3%-25.6%], respectively). Maximum hip adduction and knee valgus occurred before maximum knee flexion in women and after in men (mean differences 0.11 seconds [95% CI, 0.05-0.18 seconds], 0.19 seconds [95% CI, 0.13-0.25 seconds], respectively). Maximum ankle eversion occurred earlier in women than in men (mean difference 0.06 seconds [95% CI, 0.01-0.11 seconds]). There was a significant difference between genders for angular velocity of knee valgus (mean difference = 25.53 deg/sec [95% CI, 8.30-42.77 deg/sec]).
Conclusion: Frontal plane kinematic temporal relationships at the hip, knee, and ankle differ between genders. The components of dynamic knee valgus peak during the deceleration phase in women and during the acceleration phase in men during a drop-jump landing. These data suggest that men and women employ a completely different kinematic landing/jumping strategy and that women land and collapse very rapidly into valgus compared with their male counterparts.
Clinical Relevance: The differences in timing of the components of dynamic knee valgus between women and men may contribute to the increased risk of noncontact anterior cruciate ligament injuries in female athletes. There may be implications for neuromuscular reeducation training in those at risk for anterior cruciate ligament injury so the components of dynamic valgus occur later in the landing phase of jumping.
Background: The mechanism for noncontact anterior cruciate ligament injury is still a matter of controversy. Video analysis of injury tapes is the only method available to extract biomechanical information from actual anterior cruciate ligament injury cases.
Purpose: This article describes 3-dimensional knee joint kinematics in anterior cruciate ligament injury situations using a model-based image-matching technique.
Study Design: Case series; Level of evidence, 4.
Methods: Ten anterior cruciate ligament injury video sequences from women’s handball and basketball were analyzed using the model-based image-matching method.
Results: The mean knee flexion angle among the 10 cases was 23° (range, 11°-30°) at initial contact (IC) and had increased by 24° (95% confidence interval [CI], 19°-29°) within the following 40 milliseconds. The mean valgus angle was neutral (range, –2° to 3°) at IC, but had increased by 12° (95% CI, 10°-13°) 40 milliseconds later. The knee was externally rotated 5° (range, –5° to 12°) at IC, but rotated internally by 8° (95% CI, 2°-14°) during the first 40 milliseconds, followed by external rotation of 17° (95% CI, 13°-22°). The mean peak vertical ground-reaction force was 3.2 times body weight (95% CI, 2.7-3.7), and occurred at 40 milliseconds after IC (range, 0-83).
Conclusion: Based on when the sudden changes in joint angular motion and the peak vertical ground-reaction force occurred, it is likely that the anterior cruciate ligament injury occurred approximately 40 milliseconds after IC. The kinematic patterns were surprisingly consistent among the 10 cases. All players had immediate valgus motion within 40 milliseconds after IC. Moreover, the tibia rotated internally during the first 40 milliseconds and then external rotation was observed, possibly after the anterior cruciate ligament had torn. These results suggest that valgus loading is a contributing factor in the anterior cruciate ligament injury mechanism and that internal tibial rotation is coupled with valgus motion. Prevention programs should focus on acquiring a good cutting and landing technique with knee flexion and without valgus loading of the knee.
