Effect Of Knee Flexion Angle Research Articles

Chronic ankle instability affects the association between knee joint angle and loading: musculoskeletal simulation study

The purpose of this study was to calculate and compare (1) knee loads, (2) muscle-specific contributions to knee loads, and (3) effects of knee flexion angle on knee loads and muscle-specific load contributions during a forward jump-landing task in people with and without chronic ankle instability (CAI). Eight CAI patients and seven healthy controls performed a forward jump-landing task. We collected 3D kinematics, ground reaction force, and muscle activation and used musculoskeletal modeling. The results showed that only healthy controls exhibited an association between knee flexion angle and knee compressive impulse (r = 0.854, p = .014). The lack of association in CAI group may lead to knee instability and increase knee injury risk in people with CAI.

The deficits of isometric knee flexor strength in lengthened hamstring position after hamstring strain injury

ObjectiveTo investigate the effects of knee flexion angle on peak torque, rate of torque development (RTD) during isometric contraction and hamstring flexibility after hamstring strain injury (HSI). DesignCross-sectional. SettingControlled laboratory research. ParticipantsFourteen male athletes with a history of HSI and 14 athletes without HSI (controls). Main outcome measuresHamstring flexibility was evaluated using active knee extension test. Isometric knee flexion peak torque and RTD were determined at 30°, 60°, and 90° of knee flexion measured by an isokinetic dynamometer. ResultsIndividuals with a history of HSI had statistically significant, moderate deficits in isometric peak torque at 30° of knee flexion (P = 0.037; effect size = 0.55) in the HSI limb than in the uninjured limb, but not at 60° and 90° of knee flexion. In the control group, no significant differences in isometric peak torque at any angle were found between limbs. No differences in peak RTD and flexibility were found between limbs in both groups. ConclusionsIsometric peak torque at 30° of knee flexion was lower in the injured limb than in the uninjured limb. Isometric strength deficits after HSI tended to be affected by lengthened hamstring angles.

The Effect of Knee Flexion Angle on Contact Stress of Total Knee Arthroplasty

The effect of flexion angle on contact stress of the knee joint still open to the debate since lack of proof shown that flexion angles does effect the contact stress of Total Knee Arthroplasty (TKA). Thus the aim of this study is to investigate the effect of different flexion angle on contact stress of TKA via finite element method. The TKA is simulated using ANSYS Workbench and the applied loads are 2200 N, 3200 N and 2800 N. The Finite element Analysis (FEA) results for maximum stress of current and proposed designed were then compared. For the new proposed design, the maximum stress for 15° is 12.2 MPa, 45° is 23.6 MPa and 60° is 22.5 MPa which is lower than current design. Thus, it can be concluded that the new proposed design better than current design in term of contact stress. While, the different flexion angle do gives an impact on the performance of the TKA.

The Effect of Knee Flexion Angle During Graft Fixation on Tibiofemoral Joint Kinematics for Anterolateral Procedures when Combined with Anterior Cruciate Ligament Reconstruction

The Effect of Knee Flexion Angle During Graft Fixation on Tibiofemoral Joint Kinematics for Anterolateral Procedures when Combined with Anterior Cruciate Ligament Reconstruction

Anterolateral Tenodesis or Anterolateral Ligament Complex Reconstruction: Effect of Flexion Angle at Graft Fixation When Combined With ACL Reconstruction

Background: Despite numerous technical descriptions of anterolateral procedures, knowledge is limited regarding the effect of knee flexion angle during graft fixation. Purpose: To determine the effect of knee flexion angle during graft fixation on tibiofemoral joint kinematics for a modified Lemaire tenodesis or an anterolateral ligament (ALL) complex reconstruction combined with anterior cruciate ligament (ACL) reconstruction. Study Design: Controlled laboratory study. Methods: Twelve cadaveric knees were mounted in a test rig with kinematics recorded from 0° to 90° flexion. Loads applied to the tibia were 90-N anterior translation, 5-N·m internal tibial rotation, and combined 90-N anterior force and 5-N·m internal rotation. Intact, ACL-deficient, and combined ACL plus anterolateral-deficient states were tested, and then ACL reconstruction was performed and testing was repeated. Thereafter, modified Lemaire tenodeses and ALL procedures with graft fixation at 0°, 30°, and 60° of knee flexion and 20-N graft tension were performed combined with the ACL reconstruction, and repeat testing was performed throughout. Repeated-measures analysis of variance and Bonferroni-adjusted t tests were used for statistical analysis. Results: In combined ACL and anterolateral deficiency, isolated ACL reconstruction left residual laxity for both anterior translation and internal rotation. Anterior translation was restored for all combinations of ACL and anterolateral procedures. The combined ACL reconstruction and ALL procedure restored intact knee kinematics when the graft was fixed in full extension, but when the graft was fixed in 30° and 60°, the combined procedure left residual laxity in internal rotation (P = .043). The combined ACL reconstruction and modified Lemaire procedure restored internal rotation regardless of knee flexion angle at graft fixation. When the combined ACL reconstruction and lateral procedure states were compared with the ACL-only reconstructed state, a significant reduction in internal rotation laxity was seen with the modified Lemaire tenodesis but not with the ALL procedure. Conclusion: In a knee with combined ACL and anterolateral ligament injuries, the modified Lemaire tenodesis combined with ACL reconstruction restored normal laxities at all angles of flexion for graft fixation (0°, 30°, or 60°), with 20 N of tension. The combined ACL and ALL procedure restored intact knee kinematics when tensioned in full extension. Clinical Relevance: In combined anterolateral procedure plus intra-articular ACL reconstruction, the knee flexion angle is important when fixing the graft. A modified Lemaire procedure restored intact knee laxities when fixation was performed at 0°, 30°, or 60° of flexion. The ALL procedure restored normal laxities only when fixation occurred in full extension.

The Influence of Knee Flexion Angle for Graft Fixation on Rotational Knee Stability During Anterior Cruciate Ligament Reconstruction: A Biomechanical Study

To evaluate the effect of knee flexion angle for hamstring graft fixation, full extension (FE), or 30°, on acceleration of the knee motion during pivot-shift testing after either anatomic or nonanatomic anterior cruciate ligament (ACL) reconstruction using triaxial accelerometry. Two types of ACL reconstructions (anatomic and nonanatomic) using 2 different angles of knee flexion during graft fixation (FE and 30°) were performed on 12 fresh-frozen human knees making 4 groups: anatomic-FE, anatomic-30°, nonanatomic-FE, and nonanatomic-30°. Manual pivot-shift testing was performed at ACL-intact, ACL-deficient, and ACL-reconstructed conditions. Three-dimensional acceleration of knee motion was recorded using a triaxial accelerometer. The anatomic-30° group showed the smallest overall magnitude of acceleration among the ACL-reconstructed groups (P= .0039). There were no significant differences among the anatomic-FE group, the nonanatomic-FE group, and the nonantomic-30° group (anatomic-FE vs nonanatomic-FE, P= .1093; anatomic-FE vs nonanatomic-30°, P= .8728; and nonanatomic-FE vs nonanatomic-30°, P= .1093). After ACL transection, acceleration was reduced by ACL reconstruction with the exception of the nonanatomic-FE group that did not show a significant difference when compared with the ACL-deficient (P=.4537). The anatomic ACL reconstruction with the graft fixed at 30° of knee flexion better restored rotational knee stability compared with FE. An ACL graft fixed with the knee at FE in anatomic position did not show a significant difference compared with the nonanatomic ACL reconstructions. Knee flexion angle at the time of graft fixation for ACL reconstruction can be considered to maximize the rotational knee stability.

Upright Magnetic Resonance Imaging Tasks in the Knee Osteoarthritis Population: Relationships Between Knee Flexion Angle, Self-Reported Pain, and Performance

ObjectiveTo characterize the ability of patients with symptomatic knee osteoarthritis (OA) to perform a weight-bearing activity compatible with upright magnetic resonance imaging (MRI) scanning and how this ability is affected by knee pain symptoms and flexion angles. DesignCross-sectional observational study assessing effects of knee flexion angle, pain level, and study sequence on accuracy and duration of performing a task used in weight-bearing MRI evaluation. Visual feedback of knee position from an MRI compatible sensor was provided. Pain levels were self-reported on a standardized scale. SettingSimulated MRI setup in a research laboratory. ParticipantsConvenience sample of individuals (N=14; 9 women, 5 men; mean, 69±14y) with symptomatic knee OA. InterventionsNot applicable. Main Outcome MeasuresAveraged absolute and signed angle error from target knee flexion for each minute of trial and duration tolerance (the duration that subjects maintained position within a prescribed error threshold). ResultsAbsolute targeting error increased at longer trial durations (P<.001). Duration tolerance decreased with increasing pain (mean ± SE, no pain: 3min 19s±11s; severe pain: 1min 49s±23s; P=.008). Study sequence affected duration tolerance (first knee: 3min 5s±9.1s; second knee: 2min 19s±9.7s; P=.015). ConclusionsThe study provided evidence that weight-bearing MRI evaluations based on imaging protocols in the range of 2 to 3 minutes are compatible with patients reporting mild to moderate knee OA-related pain.

Effects of Knee Flexion Angle and Loading Conditions on the End-to-End Distance of the Posterior Cruciate Ligament

Background: It is commonly accepted that the anterolateral (AL) bundle of the posterior cruciate ligament (PCL) is tight in flexion and that the posteromedial (PM) bundle is tight in extension. However, a recent in vivo study showed that both bundles were tight in extension. Purpose: To investigate the effects of knee flexion angle, rotational torque, and anterior/posterior translational force on the end-to-end distance between the femoral and tibial insertion sites of each bundle of the PCL. Study Design: Descriptive laboratory study. Methods: Cadaveric knees (10 specimens) were mounted on a robotic system, and the relative positional data between the femur and tibia were acquired during passive flexion/extension, with an applied 5-N·m rotational torque and an applied 89-N translational force. The bony surface and PCL insertion data were acquired with a 3-dimensional scanner after gross dissection and were superimposed onto the positional data. The end-to-end distance between the 2 PCL insertion sites of the femur and tibia was measured. Results: The end-to-end distance increased from full extension to 90° for both the AL (9.2 ± 1.8 mm; from 30.0 to 39.2 mm) and PM bundles (5.8 ± 2.2 mm; from 32.0 to 37.7 mm). With an internal rotational torque, the end-to-end distance of the PM bundle increased significantly (P < .05) at 0°, 30°, and 60° of knee flexion. Under a posterior translational force at 90° of knee flexion, the length of both bundles increased to their longest measurements (AM bundle: 40.6 ± 4.2 mm; PM bundle: 38.4 ± 3.8 mm). Conclusion: The end-to-end distance of the AL and PM bundles of the PCL increased in flexion, and this pattern was maintained during tests with posterior translational force. The PM bundle was more affected by the rotational torque than was the AL bundle. Clinical Relevance: Both bundles of the PCL may serve a greater functional role in flexion than in extension. The PM bundle might be more important for the control of rotation than the AL bundle. Posterior translation at 90° of knee flexion could be the most stressful condition for both bundles of the PCL, which may have implications for an injury mechanism.

Effect of Knee Joint Angle on Side-to-Side Strength Ratios

Isometric knee extensor and flexor strength are typically tested at different joint angles due to the differences in length-tension relationships of the quadriceps and hamstring muscles. The efficiency of strength testing can be improved if the same angle can be used to test both the knee extensor and flexor muscle groups. The aim of this study was to determine an optimal angle for isometric knee strength testing by examining the effect of knee angle on side-to-side peak torque ratios. Eighteen active young people (9 males and 9 females) participated in this study. Knee extensor and knee flexor strength were tested on both sides at 30°, 60°, and 90° of knee flexion. The effect of knee flexion angle on side-to-side peak torque ratios, raw torque values, and side-to-side flexor-to-extensor torque ratios were assessed. Side-to-side knee extensor peak torque ratios and knee flexor-to-extensor torque ratios differed significantly by knee flexion angle (p = 0.024 and p = 0.011, respectively), but side-to-side knee flexor peak torque ratios did not differ significantly (p = 0.311). When considering both side-to-side peak torque ratios and flexor-to-extensor torque ratios, the values were more symmetrical (i.e., closer to 100%) only at 60° of knee flexion. Our results indicate that both the knee flexors and the knee extensors can be tested clinically at 60° of knee flexion. Our results also indicate that the hamstrings can be tested at any of the 3 angles if the examiner is interested in side-to-side ratios rather than raw torque values. These results may facilitate more efficient and flexible clinical knee strength testing.

How Different Knee Flexion Angles Influence the Hip Extensor in the Prone Position

[Purpose] The present study examined the effects of knee flexion angle on hip extensor muscle activity. [Subjects and Methods] Twenty healthy subjects maintained knee flexion angles of 0°, 30°, 60°, 90° and 110° in the prone position and performed maximal voluntary contraction in hip extension. Maximum torque in hip extension at the different angles was measured, and surface electromyogram activities of the gluteus maximus (GM), biceps femoris (BF) and semitendinosus (ST) were recorded and normalized by the maximum voluntary isometric contraction (MVIC). [Results] The maximum torque of the hip extensor showed significant decreases between 0°and 60°, 90° and 110° of knee flexion. The muscle activity of BF was significantly high at 0°, and GM showed a significantly higher activity than both BF and ST at 60°, 90°and 110° of knee flexion. [Conclusion] The maximum torque in hip extension and muscle activities of BF and ST were significantly high at 0° but they decreased at knee flexion angles of more than 60°. Therefore, we consider that more than 60° of knee joint flexion is required to increase GM activity, and to reduce the muscle activities of BF and ST.

Flexible Reamers in Anatomic ACL Reconstruction: Effect of Knee Flexion on Femoral Tunnel Length and Latrogenic Peroneal Nerve Injury (SS-67)

The purpose of this study was to determine the effect of knee flexion angle on femoral tunnel length and distance of guide pin to critical lateral knee structures with the use of a flexible guide pin and reamer system from a standard anteromedial arthroscopic portal. We obtained 10 cadaveric knees, all of which had no evidence of prior knee surgery. The intact anterior cruciate ligament was debrided and the anatomic femoral footprint was identified. Flexible guide pins were inserted from a standard anteromedial portal in knee flexion angles of 70, 90 and 120 degrees using the same starting point. Tunnel lengths were determined for each of these guide pins at each angle. Distances from the common peroneal nerve and the origin of the fibular collateral ligament were measured for each guide pin as they exited out the lateral femoral cortex. We calculated the average tunnel lengths at various flexion angles and distances to the lateral structures for each guide pin in all of the specimens. The average femoral tunnel length was found to be statistically longer with 120 degrees of knee flexion than at 70 degrees, 38.4 mm vs. 26 mm (p=0.0001). The average tunnel length was not statistically different between the 70 and 90 degree angles (26 +/− 4.18 mm and 32.4 +/− 9.24 mm respectively, p=0.08). No guide pin injured the common peroneal nerve. The mean distance to the common peroneal nerve was 50.2 mm +/− 15.53 at 70 degree knee flexion angle. This distance was significantly lower than the 120 degree flexion angle mean of 70 mm +/− 19.20 (p=0.01). Regardless of the type of guide pin and reamer system used in anatomic ACL reconstruction, knee flexion angle determines femoral tunnel length. Longer femoral tunnels were obtained with higher knee flexion angles, similar to previous studies using rigid guide pins. With flexible guide pins lower knee flexion angles provide tunnel lengths that may be sufficient for interference screw fixation but may not allow for sufficient length for suspensory or cortical fixation devices. Flexible guide pins do not put the common peroneal nerve at risk in any flexion angle.

Paper # 246: The Effect of Knee Flexion Angle and Loading Conditions on the End to End Distance of Posterior Cruciate Ligament

Paper # 246: The Effect of Knee Flexion Angle and Loading Conditions on the End to End Distance of Posterior Cruciate Ligament

Effect of knee flexion angle on ground reaction forces, knee moments and muscle co-contraction during an impact-like deceleration landing: Implications for the non-contact mechanism of ACL injury

Investigating landing kinetics and neuromuscular control strategies during rapid deceleration movements is a prerequisite to understanding the non-contact mechanism of ACL injury. The purpose of this study was to quantify the effect of knee flexion angle on ground reaction forces, net knee joint moments, muscle co-contraction and lower extremity muscles during an impact-like, deceleration task. Ground reaction forces and knee joint moments were determined from video and force plate records of 10 healthy male subjects performing rapid deceleration single leg landings from a 10.5 cm height with different degrees of knee flexion at landing. Muscle co-contraction was based on muscle moments calculated from an EMG-to-moment processing model. Ground reaction forces and co-contraction indices decreased while knee extensor moments increased significantly with increased degrees of knee flexion at landing (all p < 0.005). Higher ground reaction forces when landing in an extended knee position suggests they are a contributing factor in non-contact ACL injuries. Increased knee extensor moments and less co-contraction with flexed knee landings suggest that quadriceps overload may not be the primary cause of non-contact ACL injuries. The results bring into question the counterbalancing role of the hamstrings during dynamic movements. The soleus may be a valuable synergist stabilizing the tibia against anterior translation at landing. Movement strategies that lessen the propagation of reaction forces up the kinetic chain may help prevent non-contact ACL injuries. The relative interaction of all involved thigh and lower leg muscles, not just the quadriceps and hamstrings should be considered when interpreting non-contact ACL injury mechanisms.

Effect of Knee Flexion Angle on Length and Orientation of Posterolateral Femoral Tunnel Drilled Through Anteromedial Portal During Anatomic Double-Bundle Anterior Cruciate Ligament Reconstruction

Our purpose was to evaluate the radiologic orientation and length of the posterolateral (PL) femoral tunnel when drilled through the anteromedial (AM) portal at 90 degrees, 110 degrees, and 130 degrees of flexion. In 9 fresh cadaveric knees the anterior cruciate ligament was excised and 2.4-mm guidewires were drilled through the center of the PL bundle footprint through an accessory AM portal. Pins were advanced, in a retrograde manner, until flush with the notch wall and left in place. Outcomes were measured by use of plain anteroposterior, lateral, and tunnel radiographs to determine tunnel orientation and clock position, and direct measurement was performed to determine the intraosseous length, the shortest distance to the posterior bone cortex, and the distance to the lateral collateral ligament attachment on the lateral aspect of the femoral condyle. With regard to tunnel orientation, each increase in knee flexion angle resulted in a more horizontal tunnel on both the lateral and anteroposterior views. On the tunnel view, the PL guidewire became more vertical with knee flexion. The mean clock position was 9 o'clock (standard deviation [SD], 00:12). No significant difference in the intraosseous length of the guidewires was observed. According to our hypothesis, knee flexion influenced the PL tunnel characteristics. At 90 degrees of flexion, the guidewire may blow out the posterior cortex of the lateral femoral condyle. A PL femoral tunnel drilled through the AM portal becomes more horizontal with bending of the knee during drilling. At 90 degrees, the tunnel is at risk of back wall blowout.

The effect of intra-operative knee flexion angle on determination of graft location in the anatomic double-bundle anterior cruciate ligament reconstruction

Graft tunnel placement is the factor with most influence on the outcome of double-bundle anterior cruciate ligament (ACL) reconstruction. However the final decision for the graft location has to be decided subjectively under arthroscopy, and can be misplaced due to the effect of the knee flexion angle. The displacement of the estimated placement by surgeons from the ACL anatomical attachment is due to the knee's differing knee flexion angle. Eight cadaveric knees and an electromagnetic position recording system were employed. After digitizing the anatomical location of AM and PL bundle center, four experienced surgeons estimated the graft placement repeatedly at 70 degrees , 90 degrees and 110 degrees of knee flexion. The displacements between these two positions were calculated and analyzed separately in antero-posterior and disto-proximal directions. The displacements of the estimated AM bundle placements were 4.7 +/- 3.4 mm at 70 degrees , 4.3 +/- 2.2 mm at 90 degrees , and 6.0 +/- 2.6 mm at 110 degrees , while those of the PL bundle were 4.0 +/- 2.2 mm at 70 degrees , 3.4 +/- 1.9 mm at 90 degrees , and 4.2 +/- 2.5 mm at 110 degrees . The best results were obtained at 90 degrees of knee flexion. Additionally, the estimated placements for both AM and PL bundle were located more distally as the flexion angle increased. Our results imply that the knee should be set at 90 degrees when determining the graft placement in double-bundle reconstruction to prevent misplacement of the graft usually in a disto-proximal direction.

Effect of Knee Flexion Angle on Tunnel Length and Articular Cartilage Damage During Anatomic Double-Bundle Anterior Cruciate Ligament Reconstruction (SS-54)

Effect of Knee Flexion Angle on Tunnel Length and Articular Cartilage Damage During Anatomic Double-Bundle Anterior Cruciate Ligament Reconstruction (SS-54)

Vibration Exposure and Biodynamic Responses during Whole-Body Vibration Training

Excessive, chronic whole-body vibration (WBV) has a number of negative side effects on the human body, including disorders of the skeletal, digestive, reproductive, visual, and vestibular systems. Whole-body vibration training (WBVT) is intentional exposure to WBV to increase leg muscle strength, bone mineral density, health-related quality of life, and decrease back pain. The purpose of this study was to quantitatively evaluate vibration exposure and biodynamic responses during typical WBVT regimens. Healthy men and women (N = 16) were recruited to perform slow, unloaded squats during WBVT (30 Hz; 4 mm(p-p)), during which knee flexion angle (KA), mechanical impedance, head acceleration (Ha(rms)), and estimated vibration dose value (eVDV) were measured. WBVT was repeated using two forms of vibration: 1) vertical forces to both feet simultaneously (VV), and 2) upward forces to only one foot at a time (RV). Mechanical impedance varied inversely with KA during RV (effect size, eta(p)(2): 0.668, P < 0.01) and VV (eta(p)(2): 0.533, P < 0.05). Ha(rms) varied with KA (eta(p)(2): 0.686, P < 0.01) and is greater during VV than during RV at all KA (P < 0.01). The effect of KA on Ha(rms) is different for RV and VV (eta(p)(2): 0.567, P < 0.05). The eVDV associated with typical RV and VV training regimens (30 Hz, 4 mm(p-p), 10 min.d(-1)) exceeds the recommended daily vibration exposure as defined by ISO 2631-1 (P < 0.01). ISO standards indicate that 10 min.d(-1) WBVT is potentially harmful to the human body; the risk of adverse health effects may be lower during RV than VV and at half-squats rather than full-squats or upright stance. More research is needed to explore the long-term health hazards of WBVT.

Effect of Knee Flexion Angle and Tensile Direction on the Strength of Ligament Insertion to Bone

This study investigated how knee flexion angle and tensile direction affect the strength of anterior cruciate ligament (ACL) insertion to tibia using swine femur-ACL-tibia complexs. Four tensile tests at displacement rate of 10 mm/min were performed at flexion angles of 0°, 45°, and 90°on the condition that the tensile direction was along the tibial axias, and at flexion angle of 90° on the condition that the tensile direction was along the femoral axis. The modes of failure and load-displacement curves were measured and compared among all tensile tests. As for the mode of failure, there was a difference between the tensile direction along the tibial axis and along the femoral axis. At flexion angles of 0°, 45°, and 90°on tensile direction along the tibial axis, the ACL failure occurred initially by failure of posterior lateral bundle followed by failure of anterior medial bundle until the complete separation of ACL to tibia, whereas at flexion angle of 90 on tensile direction along the femoral axis, the avulsion fractures suddenly occurred. As for the load-displacement curve, the maximum load at flexion angle of 0° on tensile direction along the tibial axis was significantly larger than that at flexion angle of 90°. The maximum load at flexion angle of 90°on tensile direction along the femoral axis was larger than those at flexion angles of 45° and 90° on tensile direction along the tibial axis. Therefore, the strength of ACL insertion to tibia was affected by both knee flexion angle and tensile direction.

Effect of knee flexion angle on active joint stiffness.

The purpose of this study was to determine if active joint stiffness measured during maximum voluntary knee extension contractions was affected by knee flexion angle. Eighteen subjects volunteered (11 male, seven female). A stretch was imposed on isometric knee contractions performed at 30 degrees, 50 degrees, 70 degrees, 90 degrees, and 110 degrees of knee flexion. Active joint stiffness was computed from the increase in torque relative to the change in knee flexion angle for the first 50 ms of the stretch (approximately 1.5 degrees ) and corrected for effects of gravitational component due to leg mass and passive tension. There was a plateau in knee extension torque between 70 degrees and 90 degrees with lower values at all other angles (P < 0.05). Peak active joint stiffness occurred at 70 degrees with lower values (P < 0.05) at all other angles except 50 degrees. Stiffness at 70 degrees (441.1 +/- 189.9 Nm rad-1) was 49% higher than at 30 degrees and 45% higher than at 110 degrees. Active joint stiffness was dependent on knee flexion angle. Peak joint stiffness during maximal contractions occurred at, or prior to, the optimal angle for torque production for all subjects.

Paper #70 The effect of knee flexion angle at the time of graft fixation in ACL reconstruction with a patellar tendon graft

Paper #70 The effect of knee flexion angle at the time of graft fixation in ACL reconstruction with a patellar tendon graft