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Purpose Methods Results Conclusion Level of Evidence Similar to the anterior cruciate ligament, the femoral footprint of the posterior cruciate ligament (PCL) is composed of different fibre areas, possibly having distinct biomechanical functions. The aim of this study was to determine the role of different fibre areas of the femoral footprint of the PCL in restraining posterior tibial translation (PTT).A sequential cutting study was performed on eight fresh‐frozen human knee specimens, utilizing a six‐degrees‐of‐freedom robotic test setup. The femoral attachment of the PCL was divided into 15 areas, which were sequentially cut from the bone in a randomized sequence. After determining the native knee kinematics, a displacement‐controlled protocol was performed replaying the native motion, while constantly measuring the force. The reduction of the restraining force presented the percentage contribution of each cut, according to the principle of superposition.The PCL was found to contribute 29 ± 16% in 0°, 51 ± 24% in 30°, 60 ± 22% in 60° and 55 ± 18% in 90°, to restricting a PTT. The fibre areas contributing the most were located at the proximal border of the PCL footprint, away from the cartilage, and directly adjacent to the medial intercondylar ridge (p < 0.05). Of these, one fibre area showed the highest contribution at all flexion angles. This area was located at the posterior half of the medial intercondylar ridge. No clear assignment of the areas to either the anterolateral or posteromedial bundle was possible.An area towards the proximal and posterior part of the femoral PCL footprint was found to significantly restrain a posterior tibial force. Based on the data of this testing setup, a PCL graft positioned at the identified area may best mimic the part of the native PCL, which bears the most load in resisting a PTT force.No evidence level (laboratory study). [ABSTRACT FROM AUTHOR]

Purpose: To investigate the forces on a medial collateral ligament (MCL) reconstruction (MCLR) relative to the valgus alignment of the knee. Methods: Eight fresh‐frozen human cadaveric knees were subjected to dynamic valgus loading at 400 N using a custom‐made kinematics rig. After resection of the superficial medial collateral ligament, a single‐bundle MCLR with a hamstring tendon autograft was performed. A medial opening wedge distal femoral osteotomy was performed and fixed with an external fixator to gradually adjust the alignment in 5° increments from 0° to 10° valgus. For each degree of valgus deformity, the resulting forces acting on the MCLR were measured through a force sensor and captured in 15° increments from 0° to 60° of knee flexion. Results: Irrespective of the degree of knee flexion, increasing valgus malalignment resulted in significantly increased forces acting on the MCLR compared to neutral alignment (p < 0.05). Dynamic loading at 5° valgus resulted in increased forces on the MCLR at all flexion angles ranging between 16.2 N and 18.5 N (p < 0.05 from 0° to 30°; p < 0.01 from 45° to 60°). A 10° valgus malalignment further increased the forces on the MCLR at all flexion angles ranging between 29.4 N and 40.0 N (p < 0.01 from 0° to 45°, p < 0.05 at 60°). Conclusion: Valgus malalignment of the knee caused increased forces acting on the reconstructed MCL. In cases of chronic medial instabilities accompanied by a valgus deformity ≥ 5°, a realigning osteotomy should be considered concomitantly to the MCLR to protect the graft and potentially reduce graft failures. Level of Evidence: Level III. [ABSTRACT FROM AUTHOR]

Background: Conflicting evidence has been reported regarding the biomechanical relevance of ramp lesions (RLs) on knee kinematics. Furthermore, the influence of the defect size of the RLs on anterior tibial translation (ATT) and external rotation (ER) is currently unknown. Purpose: To evaluate the influence of RL defect size on knee kinematics in anterior cruciate ligament (ACL) deficiency and after simulated ACL reconstruction (sACLR). Study Design: Controlled laboratory study. Methods: Eight cadaveric knee specimens were tested in a 6 degrees of freedom robotic test setup. Force-controlled clinical laxity tests were performed with 200 N of axial compression in 0°, 30°, 60°, and 90° of flexion: 5 N·m internal rotation (IR)/ER torque, 134 N ATT force, and an anteromedial drawer test consisting of 134 N ATT force under 5 N·m ER torque. After determining the native knee kinematics, the ACL was cut at the tibial insertion, followed by a transosseous refixation to simulate a surgical repair or reconstruction (simulated ACL reconstruction; sACLR). An RL was sequentially created with a length of 1, 2, and 3 cm. Each state of the RL was evaluated in the ACL-deficient state and after sACLR. Results: In the ACL-deficient state, only an RL of 3 cm length resulted in a significant increase of ATT in 30° of flexion (mean difference 0.73 mm; 95% CI, 0.36-1.1 mm). After sACLR, an RL had no significant effect. When looking at ER, an RL significantly increased ER in full extension in the ACL-deficient state in 2 cm (mean difference 0.9°; 95% CI, 0.08°-1.74°) and 3 cm length (mean difference 1.9°; 95% CI, 0.57-3.25). Furthermore, a 3-cm RL significantly increased IR in 0° of flexion in the ACL-deficient state (mean difference 1.9°; 95% CI, 0.2°-3.6°). No effect of ramp lesions on rotation was found after sACLR. Conclusion: RLs result in a small increase in ATT, ER, and IR in ACL-deficient knees at early flexion angles, but not after sACLR. Clinical Relevance: Small RLs did not change time-zero knee kinematics and may, therefore, be left untreated, especially when the ACL is reconstructed. [ABSTRACT FROM AUTHOR]