Clinico-Radiological Correlation Between Anterior Cruciate Ligament Deficiency and Hyperextension of the Knee Joint: A Prospective Study.

INTRODUCTION: The anterior cruciate ligament (ACL) primarily restricts anterior sliding of the tibia over the fixed femur, thereby also postulating to prevent hyperextension of the knee joint. The main objective of our study was to identify the role of the ACL in the prevention of knee hyperextension and to quantify the amount of hyperextension caused by an ACL tear, apart from its well-established role in the prevention of anterior tibial translation on the fixed femur. METHODS:  This prospective study was conducted in a tertiary care hospital. Eighty patients with unilateral ACL tears were assessed clinico-radiologically in the preoperative period to quantify the knee hyperextension, which was then compared with the uninjured contralateral knee of the same patient. Posterior tibial slope and notch width index were also assessed to rule out bias in our study. RESULTS: The mean age of patients in our study was 27.3 years. Out of 80 patients, 70 were male and 10 were female. The Pearson coefficient for clinically and radiologically assessed hyperextension was 0.919 (p-value 0.001) and 0.910 (p-value 0.001), respectively. Posterior tibial slope and notch width index assessment showed Pearson coefficients of -0.018 (p-value 0.887) and -0.068 (p-value 0.547), respectively. CONCLUSION: Anterior cruciate ligament complete tear or deficiency produces knee hyperextension, which varies from patient to patient. Though the amount of hyperextension produced is mild (less than five degrees in most patients), it can cause a significant amount of knee instability. Hence, correction of knee hyperextension is crucial while performing ACL reconstruction.

Categorizing knee hyperextension patterns in hemiparetic gait and examining associated impairments in patients with chronic stroke.

BACKGROUND: Post-stroke hemiparetic gait exhibits considerable variations in motion patterns and abnormal muscle activities, notably knee hyperextension during the stance phase. Existing studies have primarily concentrated on its joint angle or moment. However, the underlying causes remain unclear. Thus, the causes of knee hyperextension were explored from a new perspective based on temporal-durational factors. RESEARCH QUESTION: Does the temporal-durational difference of knee hyperextension presence result from specific decreased motor functions? METHODS: Barefoot gait at a comfortable speed was captured using a three-dimensional camera system. Scores of knee hyperextension used a metric with the temporal-durational factor of knee hyperextension presence in each of four stance phases (1st double support, DS1; early single-leg stance, ESS; late single-leg stance, LSS; 2nd double support, DS2). These scores were used in cluster analysis. The classification and regression tree analysis characterizing each knee hyperextension cluster used the clinical measures of the lower limb and trunk motor function, muscle strength, and spasticity as explanatory variables. RESULTS: Thirty patients with hemiparetic chronic stroke who exhibited knee hyperextension during gait were included. Four knee hyperextension clusters were shown: Momentary (almost no hyperextension), Continuous (DS1-DS2), ESS-LSS, and ESS-DS2. Knee flexor strength was lower in the groups with long hyperextension durations (Continuous and ESS-DS2) compared with short durations (ESS-LSS and Momentary). ESS-DS2 exhibited higher trunk motor function than Continuous, whereas more severe spasticity was observed in ESS-LSS than in Momentary. SIGNIFICANCE: This study successfully classified four hemiparetic gait patterns with knee hyperextension based on the temporal-durational factor, providing valuable perspectives for understanding and addressing specific functional physical impairments. These findings offer guidance for focusing on related physical functions when striving for gait improvement with knee hyperextension and are expected to serve as a reference for treatment decision-making.

Does the ankle affect knee hyperextension during gait in hemiparetic stroke? A pilot study.

Background: Knee hyperextension is common following stroke because of changes in joint range of motion (ROM), muscle tone and strength on the hemiparetic side. There is no clear consensus in the literature as to the cause of knee hyperextension during the stance phase of gait. Objectives: Our study aimed to determine the feasibility of methods to investigate the association between ankle joint function and knee hyperextension in patients with hemiparetic stroke during the stance phase of gait. Methods: We used a cross-sectional observational study to assess bilateral ankle muscle strength using a handheld dynamometer, ROM using a digital inclinometer and muscle tone using the Modified Tardieu Scale. The knee angles of the hemiparetic leg during the stance phase of gait were assessed using the Kinovea movement analysis software. Data were analysed using the Statistical Package for the Social Sciences with significance level set at 0.05 and 95% confidence intervals. Results: Twelve participants were included, and no alterations were necessary to the planned methodology. We found positive associations in six participants between the tibialis anterior muscle tone and the hemiparetic knee angles during heel strike, terminal stance and pre-swing phases (p < 0.05, p < 0.01 and p < 0.01, respectively). Conclusion: The results of the data analysis suggests that there may be a correlation between tibialis anterior muscle tone and knee hyperextension, a larger study will be imperative to confirm this association. Clinical implications: The methods described in our pilot study are feasible for a larger study to be conducted with the recommendations considered.

Functional Interaction of the Cruciate Ligaments, Posteromedial and Posterolateral Capsule, Oblique Popliteal Ligament, and Other Structures in Preventing Abnormal Knee Hyperextension.

BACKGROUND: The ligaments and soft tissue capsular structures of the knee joint that provide a resisting force to prevent abnormal knee hyperextension have not been determined. This knowledge is required for the diagnosis and treatment of knee hyperextension abnormalities. PURPOSE: To determine the resisting moment of knee ligament and capsular structures that resist knee hyperextension. HYPOTHESIS: The combined posteromedial and posterolateral capsular structures function to provide a major restraint to prevent abnormal knee hyperextension. The anterior and posterior cruciate ligaments resist knee hyperextension but function as secondary restraints. STUDY DESIGN: Descriptive laboratory study. METHODS: A 6 degrees of freedom robotic system determined intact laxity limits in 24 cadaveric knees from 0° to 100° of knee flexion for anteroposterior limits at ±135 N, abduction-adduction limits at ±7 N·m, and external-internal limits at ±5 N·m. One loading method (n = 14 knees) used a static loading sequence with knee hyperextension to 27-N·m torque while maintaining all other degrees of freedom at zero load during sequential soft tissue cutting. The second method (n = 10 knees) used a cyclic loading sequence to decrease viscoelastic effects with soft tissue cutting at 0° of extension, followed by knee hyperextension to 27-N·m torque and cycled back to 0°. Selective soft tissue cuttings were performed of the following: oblique popliteal ligament, fabellofibular ligament, posterolateral capsule, posteromedial capsule with posterior oblique ligament, cruciate ligaments, lateral collateral ligament, popliteus, anterolateral ligament and iliotibial band, and superficial plus deep medial collateral ligaments. The sequential loss in the restraining moment with sectioning provides the function of that structure in resisting knee hyperextension. RESULTS: The median resisting force to knee hyperextension, in descending order, was the posteromedial capsule and posterior oblique ligament (21.7%), posterorolateral ligament and fabellofibular ligament (17.1%), anterior and posterior cruciate ligaments (13% and 12.9%, respectively), superior and deep medial collateral ligament (9.6%), oblique popliteal ligament (7.7%), and lateral collateral ligament (5.4%). The combined posterior capsular structures provided 54.7% and the anterior and posterior cruciate ligaments 25.3% of the total resisting moment to prevent knee hyperextension. CONCLUSION: Diagnosis of abnormal knee hyperextension involves a combination of multiple ligament and soft tissue structures without 1 primary restraint. The posteromedial and posterolateral capsular structures provided the major resisting moment to prevent knee hyperextension. The cruciate ligaments produced a lesser resisting moment to knee hyperextension. CLINICAL RELEVANCE: This is the first study to comprehensively measure all of the knee ligaments and capsular structures providing a resisting moment to abnormal knee hyperextension. These data are required for diagnostic and treatment strategies on the pathomechanics of abnormal knee hyperextension in patients after injury or developmental cases.

Robotized Knee-Ankle-Foot Orthosis-Assisted Gait Training on Genu Recurvatum during Gait in Patients with Chronic Stroke: A Feasibility Study and Case Report.

Genu recurvatum (knee hyperextension) is a common problem after stroke. It is important to promote the coordination between knee and ankle movements during gait; however, no study has investigated how multi-joint assistance affects genu recurvatum. We are developing a gait training technique that uses robotized knee-ankle-foot orthosis (KAFO) to assists the knee and ankle joints simultaneously. This report aimed to investigate the safety of robotized KAFO-assisted gait training (Experiment 1) and a clinical trial to treat genu recurvatum in a patient with stroke (Experiment 2). Six healthy participants and eight patients with chronic stroke participated in Experiment 1. They received robotized KAFO-assisted gait training for one or 10 sessions. One patient with chronic stroke participated in Experiment 2 to investigate the effect of robotized KAFO-assisted gait training on genu recurvatum. The patient received the training for 30 min/day for nine days. The robot consisted of KAFO and an attached actuator of four pneumatic artificial muscles. The assistance parameters were adjusted by therapists to prevent genu recurvatum during gait. In Experiment 2, we evaluated the knee joint angle during overground gait, Fugl-Meyer Assessment of lower extremity (FMA-LE), modified Ashworth scale (MAS), Gait Assessment and Intervention Tool (G.A.I.T.), 10-m gait speed test, and 6-min walk test (6MWT) before and after the intervention without the robot. All participants completed the training in both experiments safely. In Experiment 2, genu recurvatum, FMA-LE, MAS, G.A.I.T., and 6MWT improved after robotized KAFO-assisted gait training. The results indicated that the multi-joint assistance robot may be effective for genu recurvatum after stroke.

Immediate effects of a buffered knee orthosis on gait in stroke patients with knee hyperextension.

BACKGROUND: Patients exhibit considerable variations in gait patterns especially in knee hyperextension in the stance phase after stroke. If knee hyperextension is untreated it may lead to pain, reduced independence in activities of daily living, deformities and instability. OBJECTIVE: The aim of this study was to investigate the immediate effects of a buffered knee orthosis on gait of stroke patients with knee hyperextension. METHODS: A total of nine patients with knee hyperextension after stroke were selected to wear buffered knee orthosis developed by Zhongshan Traditional Chinese Medicine Hospital and Ruike Medical Technology (Shanghai) Co., Ltd during walking training and daily walking. Then the gait analysis system of Motionanalysis was used to analyze and evaluate kinematic and spatiotemporal parameters of the gait in patients with independent walking or walking with a buffered knee orthosis. RESULTS: After wearing the buffered knee brace, initial contact, maximum and minimum angles of support phase, the toe off the ground, maximum and minimum angles of swing phase on the injured side of knee and ankle increased. Minimum angle of support phase and maximum angle of swing phase on the uninjured side of ankle decreased, while the toe off the ground and minimum angles of swing phase increased significantly (all P< 0.05); There was no significant difference in other kinematics, in parameters between time and space, in walking speed among subjective gait parameters (P> 0.05). Walking distance, confidence, sense of security, and the feeling of walking hyperextension were all improved. In addition, the number of asymmetric kinematic parameters and spatiotemporal parameters decreased. CONCLUSION: The buffered knee orthosis can effectively prevent knee hyperextension after stroke, improve the knee and ankle sagittal motion, gait asymmetry, gait subjective feeling, and does not affect gait space-time parameters.

Correlation between knee hyperextension gait and lower limb muscle activation in stroke patients with hemiplegia / 中国康复理论与实践

ObjectiveTo explore the correlation among knee hyperextension angle, lower limb joints kinematics parameters and the activation of main muscles of lower limb in stroke hemiplegic patients with knee hyperextension during walking. MethodsFrom August, 2020 to September, 2021, 24 stroke hemiplegic patients with knee hyperextension and 24 healthy subjects matched with sex, age, height and body mass with knee hyperextension were analyzed with three-dimensional gait analysis system and the wireless surface electromyography acquisition system, to record the range of motion of pelvis, hip, knee and ankle joints in sagittal plane, and the activation of bilateral gluteus maximus, biceps femoris, vastus medialis and gastrocnemius medialis. ResultsAs the maximum of knee hyperextension, range of motion of the joints in sagittal plane and the activation of the muscles were different between the patients and the healthy subjects during the single-support phase of walking (|t| > 3.080, P < 0.01), and the maximum of knee hyperextension correlated with the activation of gluteus maximus in the patients (r = -0.532, P < 0.01), and the range of motion of ankle plantar flexion in both the patients and the healthy subjects (r > 0.686, P < 0.001). ConclusionThe correction for knee hyperextension gait in stroke hemiplegic patients may not only need to pay attention to knee joint control, but also need further treatment of ankle control and hip muscle function.

Determining the Roles of the Anterior Cruciate Ligament, Posterolateral Corner, and Medial Collateral Ligament in Knee Hyperextension Using the Heel-Height Test.

Background: Anterior cruciate ligament (ACL) tears are often associated with other ligamentous injuries. The side-to-side difference in heel height can represent a valuable diagnostic tool in the setting of multiligamentous injuries. Purpose: To assess in a cadaveric model how sequential sectioning of the static stabilizing structures of the knee (ACL, fibular collateral ligament [FCL], popliteus tendon [PLT], popliteofibular ligament [PFL], and medial collateral ligament [MCL]) influences heel-height measurements when comparing groups undergoing initial transection of the ACL versus FCL and to assess posterior tibial slope after sequential sectioning. Study Design: Controlled laboratory study. Methods: A total of 16 fresh cadaveric knees were carefully dissected to expose the ACL, FCL, PLT, PFL, and MCL. Each knee was randomized to either the ACL-first or FCL-first group based on the initial structure sectioned. The sectioning order was as follows: (1) ACL or FCL, (2) FCL or ACL, (3) PLT, (4) PFL, and (5) MCL. Heel height was measured with a standardized superiorly directed 12-N·m force applied to the knee while stabilizing the femur; heel height was also measured with a clinician-applied force. The measurements were compared between and within groups for each sectioned state. The correlation between tibial slope and heel-height measurements was analyzed. Results: There were no significant differences in heel-height measurements between the ACL-first and FCL-first groups (P = .863). Combined ACL-FCL injuries led to a 2.85 ± 0.83-cm increase in heel height compared to the intact state. Significant increases in heel height occurred after all sectioned states, except the PFL sectioned state. Combined ACL-posterolateral corner (PLC) injuries resulted in a 3.72 ± 1.02-cm increase in heel height, and additional sectioning of the MCL resulted in a 4.73 ± 1.35-cm increase compared to the intact state. Tibial slope was not correlated with increases in heel height after each sectioning (P = .154). Conclusion: Combined ACL-FCL, ACL-PLC, and ACL-PLC-MCL injuries resulted in increasing mean heel-height measurements (2.85, 3.72, and 4.73 cm, respectively) compared to the intact state. Tibial slope was not found to influence increases in heel height. Clinical Relevance: The side-to-side difference in heel height may be a clinically relevant examination tool for diagnosing multiligament knee injuries.

Treatment of knee hyperextension in post-stroke gait. A systematic review.

BACKGROUND: Post-stroke, patients exhibit considerable variations in gait patterns. One of the variations that can be present in post-stroke gait is knee hyperextension in the stance phase. RESEARCH QUESTION: What is the current evidence for the effectiveness of the treatment of knee hyperextension in post-stroke gait? METHODS: MEDLINE, EMBASE, PEDro, CINAHL, and the Cochrane library were searched for relevant controlled trials. Two researchers independently extracted the data and assessed the methological quality. A best evidence synthesis was conducted to summarize the results. RESULTS: Eight controlled trials (5 RCTs, 3 CCTs) were included. Three types of interventions were identified: proprioceptive training, orthotic treatment, and functional electrostimulation (FES). In the included studies, the time since the stroke occurrence varied from the (sub)acute phase to the chronic phase. Only short-term effects were investigated. The adjustment from a form of proprioceptive training to physiotherapy training programs seems to be effective (moderate evidence) for treating knee hyperextension in gait, as applied in the subacute phase post-stroke. Neither evidence for effects on gait speed nor gait symmetry were found as a result of proprioceptive training. Orthoses that cover the knee have some effects (limited evidence) on knee hyperextension and gait speed. No evidence was found for FES. SIGNIFICANCE: This is the first systematic literature review on the effectiveness of interventions on knee hyperextension in post-stroke gait. We found promising results (moderate evidence) for some "proprioceptive approaches" as an add-on therapy to physiotherapy training programs for treating knee hyperextension during the subacute phase post-stroke, in the short-term. Therefore, initially, clinicians should implement a training program with a proprioceptive approach in order to restore knee control in these patients. Because only studies reporting short-term results were found, more high-quality RCTs and CCTs are needed that also study mid- and long-term effects.

Knee Hyperextension Greater Than 5° Is a Risk Factor for Failure in ACL Reconstruction Using Hamstring Graft.

BACKGROUND: The degree of knee hyperextension in isolation has not been studied in detail as a risk factor that could lead to increased looseness or graft failure after anterior cruciate ligament (ACL) reconstruction. PURPOSE: To analyze whether more than 5° of passive knee hyperextension is associated with worse functional outcomes and greater risk of graft failure after primary ACL reconstruction with hamstring tendon autograft. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: A cohort of patients who had primary ACL reconstruction with hamstring tendon autografts was divided into 2 groups based on passive contralateral knee hyperextension greater than 5° (hyperextension group) and less than 5° (control group) of hyperextension. Groups were matched by age, sex, and associated meniscal tears. The following data were collected and compared between the groups: patient data (age and sex), time from injury to surgery, passive knee hyperextension, KT-1000 arthrometer laxity, pivot shift, associated meniscal injury and treatment (meniscectomy or repair), contralateral knee ligament injury, intra-articular graft size, follow-up time, occurrence of graft failure, and postoperative Lysholm knee scale and International Knee Documentation Committee subjective form scores. RESULTS: Data from 358 patients initially included in the study were analyzed; 22 were excluded because the time from injury to surgery was greater than 24 months, and 22 were lost to follow-up. From the cohort of 314 patients, 102 had more than 5° of knee hyperextension. A control group of the same size (n = 102) was selected by matching among the other 212 patients. Significant differences in the incidence of graft failure (14.7% vs 2.9%; P = .005) and Lysholm knee scale score (86.4 ± 9.8 vs 89.6 ± 6.1; P = .018) were found between the 2 groups. CONCLUSION: Patients with more than 5° of contralateral knee hyperextension submitted to single-bundle ACL reconstruction with hamstring tendons have a higher failure rate than patients with less than 5° of knee hyperextension.

Observation of the Therapeutic Effect of Correcting Foot Varus on Improving Knee Hyperextension and Gait in Patients After Stroke.

OBJECTIVE: The present study aimed to observe the therapeutic effect of elastic bandages on improving knee hyperextension in patients with stroke after correcting the foot varus. METHODS: A total of 45 patients with stroke admitted to the hospital from January to August 2019 were enrolled in the present prospective study. Elastic bandages were used to fix the affected foot in a mild valgus position. Before and after the intervention, the Noitom walking function evaluation system was adopted, and the Timed Up and Go (TUG) test and the 10-meter walking test were conducted. The gait speed, stride length, knee angle, and the number of knee hyperextensions >5° were selected as the results. The weight-bearing time of the affected leg was evaluated, and the changes in the control ability of the affected limb before and after the intervention were compared. RESULTS: It was found that compared with before treatment, the time of knee hyperextension was significantly reduced after fixation with the elastic bandage, and the knee extension angle was significantly reduced (p < 0.05). After the treatment, the gait speed was significantly higher than before the treatment (p < 0.05), but there was no statistically significant difference in the stride length (p > 0.05). After the treatment, the time in the TUG test was significantly shorter than before the treatment (p < 0.05), together with an obvious increase in the weight-bearing time of the affected leg (p < 0.05). CONCLUSION: Correcting foot varus could improve the biomechanics of the lower limbs and improve the symptoms of knee hyperextension in patients with stroke, thereby improving the control ability of the affected limb and improving the walking function.

Asymptomatic Genu Recurvatum reshapes lower limb sagittal joint and elevation angles during gait at different speeds.

BACKGROUND: Kinematic characteristics of walking with an asymptomatic genu recurvatum are currently unknown. The objective of this study is to characterize the lower limb sagittal joint and elevation angles during walking in participants with asymptomatic genu recurvatum and compare it with control participants without knee deformation at different speeds. METHODS: The spatio-temporal parameters and kinematics of the lower limb were recorded using an optoelectronic motion capture system in 26 participants (n = 13 with genu recurvatum and n = 13 controls). The participants walked on an instrumented treadmill during five minutes at three different speeds: slow, medium and fast. RESULTS: Participants with genu recurvatum showed several significant differences with controls: a narrower step width, a greater maximum hip joint extension angle, a greater knee joint extension angle at mid stance, a lower maximum knee joint flexion angle during the swing phase, and a greater ankle joint extension angle at the end of the gait cycle. Participants with genu recurvatum had a greater minimum thigh elevation angle, a greater maximum foot elevation angle, and a change in the orientation of the covariance plane. Walking speed had a significant effect on nearly all lower limb joint and elevation angles, and covariance plane parameters. CONCLUSION: Our findings show that genu recurvatum reshapes lower limb sagittal joint and elevation angles during walking at different speeds but preserves the covariation of elevation angles along a plane during both stance and swing phases and the rotation of this plane with increasing speed.

Risk factors for postoperative graft laxity without re-injury after double-bundle anterior cruciate ligament reconstruction in recreational athletes.

BACKGROUND: Although high activity is a risk factor for graft failure after anterior cruciate ligament (ACL) reconstruction, the risk factors for postoperative laxity after ACL reconstruction in recreational athletes are unknown. METHODS: We enrolled 91 patients (40 males, 51 females; mean age 29.2 years; mean follow-up 4.3 years) who scored ≤ 6 on the Tegner activity scale, underwent double-bundle ACL reconstruction between 2010 and 2018, and did not experience re-injury. In the stable group (75 patients, <3.0 mm side-to-side difference (SSD) in anterior translation, grade 0 or 1 pivot shift 1 year after surgery) and unstable group (16 patients, ≥3.0 mm SSD, ≥grade 2 pivot shift), multivariate logistic regression analyses adjusted for factors showing P ≤ 0.3 on univariate analysis assessed risk factors for graft laxity. Lysholm score and graft intensity on MRI (Howell grade) were compared at final follow-up. RESULTS: Mean SSD in anterior translation was 0.7 mm (stable group) and 3.3 mm (unstable group). Pivot shift grades were 0 (88%) and 1 (12%) in the stable group, and 0 (12.5%), 1 (50%), and 2 (37.5%) in the unstable group. Multivariate regression analyses showed that younger age and knee hyperextension were significant risk factors for graft laxity (P = 0.018 and 0.0016; cutoffs 18 years old and 8°, respectively). Lysholm scores in both groups were comparable, but graft intensity on MRI demonstrated significantly worse Howell grade in the unstable group (P = 0.002). CONCLUSION: Younger age and knee hyperextension were risk factors for postoperative graft laxity without re-injury in recreational athletes.

Calf lengthening may improve knee recurvatum in specific children with spastic diplegic cerebral palsy.

PURPOSE: Knee hyperextension in stance is a difficult condition to treat in children with spastic diplegic cerebral palsy (CP). In children with passive knee hyperextension, the presence of contracture or spasticity of the calf leads to knee hyperextension in stance phase. We hypothesize surgical treatment of the contracture of the calf will lead to less knee hyperextension. METHODS: We performed a retrospective review of children who were evaluated in our movement laboratory over 23 years with a diagnosis of CP Gross Motor Function Classification System I, II or III. We selected children who had passive knee hyperextension on exam and who underwent calf lengthening surgery. Children were divided into two groups: early recurvatum (ER) (n = 20) and late recurvatum (LR) (n = 14). RESULTS: There was no difference in the preoperative passive knee extension among the groups or the surgeries performed. For children who had passive knee hyperextension, calf lengthening improved static dorsiflexion with knee flexion on clinical exam by 9.3° in the ER group, 9.6° in the LR group as well as dorsiflexion with knee extension on clinical exam by 9.5° in the ER group and 6.4° in the LR group. The kinematic data showed that the ER group improved their knee hyperextension by 11° (p < 0.001), whereas the LR group did not significantly change their stance phase knee position. CONCLUSION: Children with passive knee hyperextension who have a calf contracture and walk in knee hyperextension in the first half of stance phase may improve after calf lengthening.Level of Evidence: III.

Surgical outcomes after single event multilevel surgery in cerebral palsy patients with mid-stance knee hyperextension.

BACKGROUND: Some patients with cerebral palsy (CP) exhibit excessive knee flexion at initial contact followed by knee hyperextension (KE) in mid-stance. RESEARCH QUESTION: This study investigated the change in sagittal kinematics after distal hamstring lengthening (DHL) and triceps surae lengthening procedures in CP patients with KE, and compared it to those without KE. In addition, the risk factors for the worsening of postoperative KE were analyzed. METHODS: Consecutive 312 patients (596 limbs) with CP who underwent DHL and triceps surae lengthening were included. All patients underwent preoperative and 1-year postoperative three-dimensional gait analysis. Patients' limbs were divided into the KE and knee flexion (KF) groups, according to preoperative minimum knee flexion in stance. KE was defined as minimum knee flexion in stance less than 0°. RESULTS: The KE and KF groups included 130 and 466 limbs, respectively. Knee and ankle sagittal kinematics significantly improved after surgery in both groups. Minimum knee flexion in stance significantly increased from -6.6˚ to 0.5˚ in the KE group, but decreased from 14.6˚ to 7.8˚ in the KF group. Among the KE group, minimum knee flexion in stance improved in 103 limbs (79.2 %), but worsened in 27 limbs (20.8 %). Degree of preoperative KE was the only factor significantly associated with postoperative worsening of KE (p=0.002). The cutoff value for the worsening of KE was -5.8˚ of preoperative minimum knee flexion in stance. SIGNIFICANCE: This study demonstrated that the sagittal kinematics of the knee and ankle joints improved after DHL and triceps surae lengthening procedures in CP patients with and without KE. Preoperative degree of KE was a risk factor for the worsening of KE after surgery. Therefore, careful selection for indication of DHL is required to prevent postoperative KE due to overlengthening of the hamstrings, particularly in patients with severe preoperative KE.

Knee hyperextension and a small lateral condyle are associated with greater quantified antero-lateral rotatory instability in the patients with a complete anterior cruciate ligament (ACL) rupture.

PURPOSE: To identify factors associated with quantified rotatory stability (pivot-shift phenomenon) in the anterior cruciate ligament (ACL)-injured knee joint. METHODS: A consecutive sample of 54 patients who were diagnosed with an ACL injury and admitted to our hospital to undergo ACL reconstruction were enrolled in this study. Antero-lateral rotatory laxity of the knee joint was quantified using a Kinematic Rapid Assessment device (KiRA; Orthokey LTD) under spinal block before initiating reconstruction of the ACL. Univariate and multivariate regressions were performed assuming relationships between patient characteristics (independent variables) and quantified antero-lateral rotatory stability (a dependent variable). RESULTS: It was observed that a low BMI (t = - 1.659, n.s.), greater passive knee extension angle (t = 2.374, P = 0.023), and a narrower lateral femoral condyle width index (t = - 1.712, n.s.) could be candidates associated with the antero-lateral rotatory instability, using univariate analysis. Employing multivariate analysis controlling for these three variables, that the range of passive knee extension was found to be significantly associated with antero-lateral rotatory instability in the ACL-injured knee joint (t = 2.21, P = 0.035). Patients were then divided into two groups (pivot-shift negative versus positive groups) based on the KiRA-documented quantified pivot-shift test. Interestingly, 23.3% of patients were pivot-shift negative, even though their ACL was confirmed as a complete rupture by arthroscopic observations. The degree of passive knee extension was 2.3 ± 4.5 (mean ± SD) in the pivot-shift negative group, while it was 6.8 ± 6.6 in the pivot-shift positive group (n.s.). The lateral femoral condyle width index was 36.6 ± 2.0% in the pivot-shift negative group, and it was significantly wider than in the pivot-shift positive group (33.8 ± 2.6%, P = 0.0046). Finally, we estimated that the risk of positive pivot-shift depends on the degree of knee extension. The logistic regression analysis revealed that genu recurvatum significantly increased the odds ratio for positive pivot-shift (OR = 3.08, P = 0.047, 95% CI = 1.017-9.350). CONCLUSIONS: This study revealed that greater antero-lateral rotatory instability in patients with a complete ACL rupture was associated with genu recurvatum and small lateral femoral condyle. These factors should be considered as predictors of a poor outcome from an ACL reconstruction due to a higher load on the ACL graft, and therefore, the attending physicians should modify the treatment strategies accordingly. This study indicates that joint hyperlaxity and bone morphology contribute to the rotational stability of the knee joint, in addition to the ACL and antero-lateral complex (ALC). LEVEL OF EVIDENCE: IV.

Contralateral knee hyperextension is associated with increased anterior tibial translation and fewer meniscal injuries in the anterior cruciate ligament-injured knee.

PURPOSE: To investigate the influence of hyperextension of the contralateral healthy knee on anterior tibial translation (ATT) and the presence of associated injuries in the anterior cruciate ligament (ACL)-injured knee. METHODS: A local patient data register containing the surgical and clinical data of patients undergoing ACL reconstruction was analyzed. Patients were divided into groups according to the degree of hyperextension of the contralateral knee: normal (Group A ≤ 0°), mild (Group B 1°-5°), moderate (Group C 6°-10°), and severe (Group D > 10°). The ATT was measured in both knees preoperatively and 6 months postoperatively using the KT-1000 arthrometer. The presence of associated meniscal and cartilage injuries was noted. Using multivariate analysis, Groups B, C, and D were compared with Group A, using this group as a reference. RESULTS: A total of 10,957 patients were available in the register and 8502 (Group A n = 4335, Group B n = 3331, Group C n = 771, Group D n = 65) were included in the final analysis. Groups B (10.3 mm; 95% CI 0.06-0.042, p < 0.0001) and C (10.6 mm; 95% CI 0.23-0.89, p = 0.006) showed significantly greater preoperative ATT in the injured knee compared with the control group (10.1 mm). Moreover, at the 6-month follow-up, greater ATT was observed for Groups B (8.5 mm; 95% CI 0.13-0.45, p < 0.0001), C (8.5 mm; 95% CI 0.02-0.60, p = 0.035), and D (9.1 mm; 95% CI - 0.08-1.77, p = 0.082) compared with Group A (8.2 mm). Meniscal injuries were less frequent in patients with contralateral hyperextension [Group B 903 (27.1%) p < 0.0001, Group C 208 (27.0%) p = 0.0003, and Group D 12 (18.5%), 0.012] compared with the control group [Group A 1479 (34.1%)]. CONCLUSION: Contralateral knee hyperextension is associated with greater pre- and postoperative ATT in the ACL-injured knee. In patients with contralateral knee hyperextension, concomitant injuries to the menisci are less frequent. Surgeons should consider grafts with superior properties regarding postoperative anteroposterior laxity to patients with contralateral knee hyperextension. LEVEL OF EVIDENCE: Retrospective cohort study, Level IV.

Isolated Tearing and Avulsion of the Distal Biceps Femoris Tendon During Sporting Activities: A Systematic Review.

BACKGROUND: Isolated tearing and avulsions of the distal biceps femoris sustained during sporting activities are uncommon. PURPOSE: To systematically review the literature to identify distal biceps femoris tears and avulsions experienced during sporting activities to determine injury prevalence, sporting activities/mechanisms, management, and time to return to sport. STUDY DESIGN: Systematic review; Level of evidence, 4. METHODS: A systematic review was conducted investigating studies published between January 1970 and December 2017 that reported on athletes sustaining tears and avulsions of the distal biceps femoris during sporting activity. The review followed the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines and used the PubMed, Biosis Previews, SPORTDiscus, PEDro, and EMBASE databases. Inclusion criteria were studies reporting on (1) partial or complete tears and avulsions of the distal biceps femoris with documented sporting activity causing injury, (2) injury management (operative vs nonoperative), and (3) patient outcome. Exclusion criteria consisted of studies reporting on (1) distal biceps femoris injuries without tearing, (2) injuries secondary to nonsporting activities (mechanical falls, trauma), (3) concomitant injuries to adjacent structures about the knee, and (4) studies not reporting injury management or patient outcomes. Sporting activities, injury characteristics, management, and time to return to sport were analyzed. RESULTS: A total of 22 athletes with isolated distal biceps femoris tears or avulsions were identified. Injuries were predominantly associated with noncontact knee hyperextension with concurrent hip flexion during soccer or track and field, most commonly isolated to the musculotendinous junction. Injuries were treated surgically in 91% (20/22) of athletes. Mean (±SD) overall time to return to sport was 4.9 ± 3.3 months, and for athletes who underwent operative repair, there were no significant postoperative differences based on injury location (musculotendinous junction vs avulsion, P = .25) or injury severity (partial vs complete injury, P = .13). CONCLUSION: Isolated distal biceps femoris injuries occurred primarily via noncontact mechanisms. The majority of cases were treated surgically, with successful return to sport at preinjury levels. No significant difference in return to sport was appreciated based on injury location or severity. Further studies are necessary to determine the impact of treatment method.

Physiologic Preoperative Knee Hyperextension Is a Predictor of Failure in an Anterior Cruciate Ligament Revision Cohort: A Report From the MARS Group.

BACKGROUND: The occurrence of physiologic knee hyperextension (HE) in the revision anterior cruciate ligament reconstruction (ACLR) population and its effect on outcomes have yet to be reported. Hypothesis/Purpose: The prevalence of knee HE in revision ACLR and its effect on 2-year outcome were studied with the hypothesis that preoperative physiologic knee HE ≥5° is a risk factor for anterior cruciate ligament (ACL) graft rupture. STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: Patients undergoing revision ACLR were identified and prospectively enrolled between 2006 and 2011. Study inclusion criteria were patients undergoing single-bundle graft reconstructions. Patients were followed up at 2 years and asked to complete an identical set of outcome instruments (International Knee Documentation Committee, Knee injury and Osteoarthritis Outcome Score, WOMAC, and Marx Activity Rating Scale) as well as provide information regarding revision ACL graft failure. A regression model with graft failure as the dependent variable included age, sex, graft type at the time of the revision ACL surgery, and physiologic preoperative passive HE ≥5° (yes/no) to assess these as potential risk factors for clinical outcomes 2 years after revision ACLR. RESULTS: Analyses included 1145 patients, for whom 2-year follow-up was attained for 91%. The median age was 26 years, with age being a continuous variable. Those below the median were grouped as "younger" and those above as "older" (age: interquartile range = 20, 35 years), and 42% of patients were female. There were 50% autografts, 48% allografts, and 2% that had a combination of autograft plus allograft. Passive knee HE ≥5° was present in 374 (33%) patients in the revision cohort, with 52% being female. Graft rupture at 2-year follow-up occurred in 34 cases in the entire cohort, of which 12 were in the HE ≥5° group (3.2% failure rate) and 22 in the non-HE group (2.9% failure rate). The median age of patients who failed was 19 years, as opposed to 26 years for those with intact grafts. Three variables in the regression model were significant predictors of graft failure: younger age (odds ratio [OR] = 3.6; 95% CI, 1.6-7.9; P = .002), use of allograft (OR = 3.3; 95% CI, 1.5-7.4; P = .003), and HE ≥5° (OR = 2.12; 95% CI, 1.1-4.7; P = .03). CONCLUSION: This study revealed that preoperative physiologic passive knee HE ≥5° is present in one-third of patients who undergo revision ACLR. HE ≥5° was an independent significant predictor of graft failure after revision ACLR with a >2-fold OR of subsequent graft rupture in revision ACL surgery. Registration: NCT00625885 ( ClinicalTrials.gov identifier).

[Research progress on hyperextension tibial plateau fractures].

Objective: To summarize the progress in the treatment of hyperextension tibial plateau fractures. Methods: Related literature concerning hyperextension tibial plateau fractures was reviewed and analyzed in terms of injury mechanisms, clinical patterns, and treatment outcomes. Results: Hyperextension tibial plateau fractures is a specific type of hyperextension knee injuries, which is happened with the knee in over-extended position (<0°) and characterized by fracture and concomitant ligament injury. It can be classified into 4 patterns: marginal avulsion fractures, unicondylar anteromedial fractures, anterolateral fractures, and bicondylar fractures. The failure of structures occurs according to the diagonal injury mechanism characterized by anterior compression fractures and posterior tension ruptures. It is noted as a rule that a smaller anterior fragment is more likely to accompany by a posterior ligament rupture. Unicondylar anteromedial fracture pattern is caused by hyperextension varus mechanism and usually accompanied by posterolateral corner rupture. Bicondylar hyperextension injury is characterized by posterior metaphyseal cortical tension rupture, anterior articular depression, and reversed posterior slope. Conclusion: Currently there is no consensus on the treatment of hyperextension tibial plateau fractures. Further basic and clinical studies are needed.