Medial restraints to anterior-posterior motion of the knee

Evaluation under loading detects medial meniscus extrusion in patients with reconstructed anterior cruciate ligament and restricted knee extension

PURPOSE

Some patients who undergo anterior cruciate ligament (ACL) reconstruction experience abnormal mechanical stress in the meniscus. Medial meniscal extrusion (MME) is reflected in the pathological condition of the meniscus, which expands owing to repetitive mechanical stress. Thus, the effect of the reconstructed ACL on increasing MME under weight-bearing conditions remains unclear. This study investigated the effect of ACL reconstruction on meniscal extrusion under non-weight-bearing and weight-bearing conditions.

METHODS

Seventeen patients who underwent unilateral ACL reconstruction (ACL group) and 20 age-matched healthy volunteers (control group) were enrolled. Ultrasonography was performed in the supine, standing, and walking positions in preoperative and postoperative ACL patients. MME during walking was evaluated based on the dynamic behavior of extrusion, and kinetic and kinematic data were synchronously obtained. Moreover, the ACL group underwent magnetic resonance imaging (MRI) evaluation at two points: preoperatively and 12 months postoperatively, and the ultrasound findings were compared.

RESULTS

MME in the supine position measured using both ultrasonography and MRI was not significantly different preoperatively and postoperatively in the ACL group. However, postoperative MME and dynamic behavior of extrusion under standing and walking conditions were significantly higher than those in the preoperative state (dynamic behavior: 0.9 ± 0.4 mm preoperatively, 1.2 ± 0.4 mm postoperatively). Moreover, the deficits in knee extension during walking persisted postoperatively and were significantly higher than those in the control group.

CONCLUSION

MME in patients with ACL reconstruction including meniscus repair was different under mechanical stress compared to the non-weight bearing condition.

Medial Meniscectomy at the Time of ACL Reconstruction Is Associated With Postoperative Anterior Tibial Translation: A Retrospective Analysis

Background

Medial meniscal pathology and management have not been associated with postoperative anterior tibial translation (ATT) after anterior cruciate ligament reconstruction (ACLR).

Purpose

The purpose of this study was to evaluate the role of medial meniscal injury and treatment on pre- and postoperative ATT in the setting of primary ACLR. More specifically, the association between repairable medial meniscal tears, medial meniscectomy, and postoperative ATT, along with rates of revision surgery, was examined.

Study Design

Cohort study; Level of evidence, 3.

Methods

A retrospective review was performed for patients who underwent ACLR between January 1, 2010 and December 31, 2015 at a single center. Descriptive data were obtained from an institutional database for a total of 396 patients included in this study and followed for 1 year postoperatively. Statistical analysis was performed to examine associations of meniscal treatment with postoperative ATT measurements made by KT-1000 arthrometer.

Results

A total of 243 patients underwent isolated ACLR with autograft, 72 patients underwent autograft ACLR and partial medial meniscectomy (MMx) (ACLR + MMx), and 81 patients underwent autograft ACLR and medial meniscal repair (MMR) (ACLR + MMR). Patients with ACLR + MMx had higher mean age and body mass index compared with patients in the other groups. Patients who underwent ACLR + MMx had greater postoperative side-to-side ATT compared with patients undergoing ACLR (1.55 mm vs 1.07 mm; P = .04) or patients undergoing ACLR + MMR (1.55 mm vs 1.01 mm; P = .03). The ACLR + MMx group was less likely to have symmetric (<3-mm side-to-side difference) postoperative ATT compared with the ACLR group (85% vs 93%; P = .03). There was no difference in postoperative ATT between ACLR and ACLR + MMR. Postoperative return to the operating room was greater in the ACLR + MRR group compared with the ACLR + MMx group (21.9% vs 8.2%; P = .05).

Conclusion

MMx at the time of ACLR led to higher postoperative ATT compared with isolated ACLR or ACLR + MMR.

All the menisco-ligamentary structures of the medial plane play a significant role in controlling anterior tibial translation and tibial rotation of the knee. Cadaveric study of 29 knees with the Dyneelax® laximeter

Purpose

This study aimed to determine the respective roles of the anterior cruciate ligament (ACL) and the different components of the medial plane in the control of anterior tibial translation and internal and external tibial rotation.

Methods

Twenty-nine fresh lower limbs, disarticulated at the hip, were tested in the anatomy laboratory. The following structures were isolated: the ACL, the anteromedial retinaculum (AMR), the medial collateral ligament (superficial and deep MCL), the posterior medial capsule (PMC) and the posterior horn of the medial meniscus (PHMM). The lower limb was positioned at 30° of flexion on the Dyneelax® laximeter (0.1 mm and 0.1° accuracies) and underwent anterior loads up to 200 N and internal and external tibial rotations sectioned from front to back. and the knee was then retested. The results were presented as relative gains in translation and rotations for each structure. Student's t test and Wilcoxon tests were used.

Results

The relative gains in translation for the ACL, AMR, superficial MCL, deep MCL, PMC and PHMM, respectively, were 42.9%, 6.7%, 7.4%, 6%, 7.5% and 11.6%. The relative gains in internal rotation for ACL, AMR, superficial MCL, deep MCL, PMC and PHMM, respectively, were 13%, 6.9%, 4.6%, 3.9%, 13% and 8%. The relative gains in external rotation for ACL, AMR, superficial MCL, deep MCL, PMC and medial meniscus, respectively, were 8.9%, 6%, 9.7%, 13.8%,11.2% and 8.5%. All the relative gains in translation, internal and external rotations were significant at each step of transection (p < 0.01).

Conclusions

The ligamentous structures of the medial plane constitute a functional unit in which each component has a specific passive contribution. This study highlights the importance of recognising the extent of the medial ligament tears and performing a medial side anatomic and individual reconstruction and a suture of a ramp lesion, in addition to an ACL surgery.

An MCL internal brace can withstand cyclic fatigue loading and produce a valgus load to failure similar to that of intact knees

PURPOSE

The purpose of this study is to report on the biomechanical durability and strength of an MCL internal brace construct. The null hypothesis is that there will be no difference between this construct and the intact MCL in terms of deflection during fatigue testing and the ultimate failure load.

METHODS

Eight cadaver knees were used. A grade 3 equivalent MCL tear was created with both the superficial and deep femoral MCL severed. An internal brace was created by placing a cortical button and loop through the center of the femoral MCL origin and secured on the lateral cortex of the distal femur. A FiberTape (Arthrex, Naples, FL) was looped through the cortical button loop and was secured in the center of the tibial insertion of the MCL. After pre-cycling, the specimens underwent 1000 cycles of compressive load between 100 and 300 N, using four point bending testing into direct valgus. Pre and post testing deflection was measured using three dimensional motion data from two sets of reflective markers. A load-to-failure test was then conducted with failure defined as the first significant decrease in the load-displacement curve.

RESULTS

The mean increase in deflection between pre- and post-testing was 0.6° (SD ± 0.3°). The mean failure bending moment was 122.4 Nm (SD ± 29 Nm).

CONCLUSION

The internal brace construct employed in this study was able to withstand cyclic fatigue loading and recorded a valgus load to failure similar to that of intact knees. It is important for clinicians who are considering using this commercially available technique to be aware of how the construct performs under cyclic loading compared to the intact MCL.

Guided-Motion Bicruciate-Stabilized Total Knee Arthroplasty Reproduces Native Medial Collateral Ligament Strain

Background and Objectives: Guided-motion bicruciate-stabilized (BCS) total knee arthroplasty (TKA) includes a dual cam-post mechanism with an asymmetric bearing geometry that promotes normal knee kinematics and enhances anterior-posterior stability. However, it is unclear whether the improved biomechanics after guided-motion BCS TKA reproduce soft tissue strain similar to the strain generated by native knees. The purpose of this cadaveric study was to compare medial collateral ligament (MCL) strain between native and guided-motion BCS TKA knees using a video extensometer. Materials and Methods: Eight cadaver knees were mounted onto a customized knee squatting simulator to measure MCL strain during flexion in both native and guided-motion BCS TKA knees (Journey II-BCS; Smith & Nephew, Memphis, TN, USA). MCL strain was measured using a video extensometer (Mercury® RT RealTime tracking system, Sobriety s.r.o, Kuřim, Czech Republic). MCL strain level and strain distribution during knee flexion were compared between the native and guided-motion BCS TKA conditions. Results: The mean and peak MCL strain were similar between native and guided-motion BCS TKA knees at all flexion angles (p > 0.1). MCL strain distribution was similar between native and BCS TKA knees at 8 of 9 regions of interest (ROIs), while higher MCL strain was observed after BCS TKA than in the native knee at 1 ROI in the mid portion of the MCL at early flexion angles (p < 0.05 at ≤30° of flexion). Conclusions: Guided-motion BCS TKA restored the amount and distribution of MCL strain to the values observed on native knees.

Association of Meniscus Injuries in Patients With Anterior Cruciate Ligament Injuries

Introduction: In today's orthopaedic practice, meniscus and anterior cruciate ligament (ACL) injuries are prevalent. It is more common in sports injuries and automobile accidents. In patients with ACL tears, meniscus problems are also common. Several studies have linked meniscus injuries to the development of osteoarthritis in early stages. Early onset of osteoarthritis has been observed in ACL-repaired patients with meniscus tears. As a result, meniscus tears should be detected and corrected as soon as possible to avoid degenerative changes in the knee joint. The goal of the study was to see if there was a link between meniscus injuries and ACL injuries in our rural community.

Methods: This retrospective study was conducted on 48 patients at the R.L. Jalappa Hospital & Research Centre from January 2012 to December 2019. Patients between the ages of 18-65 diagnosed with ACL tear with/without meniscus damage in their knees were included in the study. Patients with posterior cruciate ligament (PCL) tear, medial collateral ligament (MCL) or lateral collateral ligament (LCL) injury, previously operated index knees, and patients with more than grade 3 knee osteoarthritis (Kellgren and Lawrence classification) were excluded. Clinical assessment of patients with knee injuries, MRI and diagnostic arthroscopy of the knee joint details were collected. After obtaining the data, we estimated the incidence of meniscus injuries associated with chronic ACL injuries. We also calculated the percentage of side/laterality injury (medial meniscus or lateral meniscus) and part of meniscus injury (anterior horn, body, and posterior horn) in chronic ACL-deficient knees. Patient characteristics such as age and gender were correlated with functional knee assessment using a modified Lysholm score. P-value and chi-square tests were used to assess the data. P-value of less than 0.5 was considered significant.

Results: Average age of the participants was 32.31 years. There were 42 men and six women in the group. Isolated medial meniscus, lateral meniscus, and combined medial and lateral meniscus had average ages of 31.83, 31.16, and 40.28 years, respectively. ACL injuries on the right side were seen in 23 patients the left side was seen in 25 patients. In comparison to the right side, the isolated medial meniscus injury on the left side was more severe. In case of a combination of medial and lateral meniscus tears, the right side suffered more damage than the left. Eleven patients had an isolated ACL tear without a meniscus injury, while the other 37 had a meniscus injury and an ACL tear. Excellent scores were observed in 11 cases, satisfactory scores in 26, and unsatisfactory in 11 cases. Age group was categorized into three groups, less than 30, 30-45, and more than 45 years. Excellent, satisfactory, and unsatisfactory scores were observed in seven, eleven, and seven patients on the left side and excellent, satisfactory, and unsatisfactory scores in four, fifteen, and four patients on the right side, respectively. P-value was not statistically significant when comparing outcomes by age, gender, or side.

Conclusion: Meniscus injuries occurred 77% of the time when there was a persistent ACL injury. In comparison to a lateral meniscus injury, the incidence of medial meniscus injury associated with chronic ACL tear was higher. In comparison to the anterior horn and body of the medial meniscus, the majority of medial meniscus tears were found in the posterior horn. 

Medial Collateral Ligament Reconstruction for Anteromedial Instability of the Knee: A Biomechanical Study In Vitro

BACKGROUND

Although a medial collateral ligament (MCL) injury is associated with anteromedial rotatory instability (AMRI) and often with an anterior cruciate ligament (ACL) injury, there has been little work to develop anteromedial (AM) reconstruction to address this laxity.

PURPOSE

To measure the ability of a novel "anatomic" AM reconstruction technique to restore native knee laxity for isolated AM insufficiency and combined AM plus posteromedial insufficiency.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 12 cadaveric knees were mounted in a kinematic testing rig that allowed the tibia to be loaded while the knee flexed-extended 0° to 100° with 88-N anteroposterior translation, 5-N·m internal rotation-external rotation (ER), 8-N·m valgus, and combined anterior translation plus ER to simulate AMRI. Joint motion was measured using optical trackers with the knee intact, after superficial MCL (sMCL) and deep MCL (dMCL) transection, and after AM reconstruction of the sMCL and dMCL with semitendinosus autografts. The posteromedial capsule (PMC)/posterior oblique ligament (POL) was then transected to induce a grade 3 medial injury, and kinematic measurements were repeated afterward and again after removing the grafts. Laxity changes were examined using repeated-measures analysis of variance and post-testing.

RESULTS

sMCL and dMCL deficiency increased valgus, ER, and AMRI laxities. These laxities did not differ from native values after AM reconstruction. Additional PMC/POL deficiency did not increase these laxities significantly but did increase internal rotation laxity near knee extension; this was not controlled by AM reconstruction.

CONCLUSION

AM reconstruction eliminated AMRI after transection of the dMCL and sMCL, and also eliminated AMRI after additional PMC/POL transection.

CLINICAL RELEVANCE

Many MCL injuries occur in combination with ACL injuries, causing AMRI. These injuries may rupture the AM capsule and dMCL. Unaddressed MCL deficiency leads to an increased ACL reconstruction failure rate. A dMCL construct oriented anterodistally across the medial joint line, along with an sMCL graft, can restore native knee ER laxity. PMC/POL lesions did not contribute to AMRI.

Meniscal Ramp Lesions: What the Radiologist Needs to Know

Meniscal ramp lesions are a special type of injury that affects the periphery of the posterior horn of the medial meniscus (PHMM) and/or its meniscocapsular attachments. They are strongly associated with acute and chronic anterior cruciate ligament (ACL) tears. These lesions have gained much prominence in recent years, due to a significant increase in their diagnosis and their important biomechanical involvement in the knee. It is known that their presence in ACL-deficient knees is related to instability and if they are not repaired during ACL reconstruction, they can ultimately cause the failure of the graft. Since this type of injury is often underdiagnosed due to its localization at the "blind" point of arthroscopic vision, it is crucial to make an accurate preoperative diagnosis of them with MRI. The objective of this article is to review the recent literature regarding meniscal ramp lesions and to summarize the anatomical, biomechanical and fundamentally diagnostic aspects, emphasizing the radiological findings described until now.

The Medial structures of the knee have a significant contribution to posteromedial rotational laxity control in the PCL-deficient knee

PURPOSE

Various reconstruction techniques have been employed to restore normal kinematics to PCL-deficient knees; however, studies show that failure rates are still high. Damage to secondary ligamentous stabilizers of the joint, which commonly occurs concurrently with PCL injuries, may contribute to these failures. The main objective of this study was to quantify the biomechanical contributions of the deep medial collateral ligament (dMCL) and posterior oblique ligament (POL) in stabilizing the PCL-deficient knee, using a joint motion simulator.

METHODS

Eight cadaveric knees underwent biomechanical analysis of posteromedial stability and rotatory laxity using an AMTI VIVO joint motion simulator. Combined posterior force (100 N) and internal torque (5 Nm) loads, followed by pure internal/external torques (± 5 Nm), were applied at 0, 30, 60 and 90° of flexion. The specimens were tested in the intact state, followed by sequential sectioning of the PCL, dMCL, POL and sMCL. The order of sectioning of the dMCL and POL was randomized, providing n = 4 for each cutting sequence. Changes in posteromedial displacements and rotatory laxities were measured, as were the biomechanical contributions of the dMCL, POL and sMCL in resisting these loads in a PCL-deficient knee.

RESULTS

Overall, it was observed that POL transection caused increased posteromedial displacements and internal rotations in extension, whereas dMCL transection had less of an effect in extension and more of an effect in flexion. Although statistically significant differences were identified during most loading scenarios, the increases in posteromedial displacements and rotatory laxity due to transection of the POL or dMCL were usually small. However, when internal torque was applied to the PCL-deficient knee, the combined torque contributions of the dMCL and POL towards resisting rotation was similar to that of the sMCL.

CONCLUSION

The dMCL and POL are both important secondary stabilizers to posteromedial translation in the PCL-deficient knee, with alternating roles depending on flexion angle. Thus, in a PCL-deficient knee, concomitant injuries to either the POL or dMCL should be addressed with the aim of reducing the risk of PCL reconstruction failure.

Isolated Meniscal Ramp Lesion Without Obvious Anterior Cruicate Ligament Rupture

OBJECTIVES

The purpose of the present paper was to study isolated meniscal ramp lesions without obvious ACL rupture. Their biomechanical mechanisms were analyzed and their clinical characteristics were reviewed. The clinical effects of an all-inside horizontal mattress suture for isolated ramp lesions were evaluated.

MATERIALS AND METHODS

Twenty isolated meniscal ramp lesion patients without obvious ACL rupture from 2015 to 2017 were retrospectively reviewed. Preoperative MRI showed intact ACL and signs of ramp lesions. These isolated ramp lesions were arthroscopically confirmed and repaired through an all-inside horizontal mattress suturing method. MRI was performed 3 months postoperatively to assess isolated ramp lesion healing. The Tegner-Lysholm score and the visual analog scale score were recorded preoperatively and at 2 years postoperatively. The Wilcoxon rank sum test was performed to determine statistical significance.

RESULTS

Arthroscopic exploration confirmed isolated ramp lesions and longitudinal ACL splits or degeneration without obvious ACL rupture. MRI 3 months postoperatively showed healing of the isolated ramp lesions. At 2 years postoperatively, the VAS scores were significantly decreased and the Tegner-Lysholm scores were significantly increased. Knee function, without pain, was restored in all patients, including walking, climing and descending stairs, and squatting.

CONCLUSION

Isolated meniscal ramp lesions without obvious ACL rupture may exist because of ACL longitudinal splits or degeneration and can be repaired through anterolateral and anteromedial portals with an all-inside horizontal-mattress suturing method.

Role of the Meniscofemoral Ligaments in the Stability of the Posterior Lateral Meniscus Root After Injury in the ACL-Deficient Knee

» Injuries to the posterior root of the lateral meniscus occur frequently in acute knee injuries with concomitant tearing of the anterior cruciate ligament (ACL). » The meniscofemoral ligaments (MFLs), consisting of the anterior MFL (ligament of Humphrey) and the posterior MFL (ligament of Wrisberg), as well as the osseous attachment of the meniscal root, stabilize the lateral meniscus, enabling appropriate load transmission and maintenance of contact forces within the lateral compartment of the knee during loading and range of motion. » In the setting of an ACL injury to the knee with osseous root injury of the posterior root of the lateral meniscus, the MFLs (when present) may stabilize the lateral meniscus against meniscal extrusion, thereby maintaining appropriate contact mechanics within the knee, decreasing the risk of subsequent chondral and meniscal injury and the development of premature osteoarthritis. » Additional study on the indications for posterior meniscal root repair during ACL reconstruction is warranted since the ideal management of lateral root injury in the MFL-intact knee remains unknown.

Outcomes of arthroscopic repair using the all-inside inter-leaf vertical suture technique for horizontal meniscal tears sustained in sports

The aim of the study was to evaluate the outcomes of arthroscopic repair using the all-inside inter-leaf vertical suture arthroscopic technique for sports-related horizontal meniscal tears.The inter-leaf vertical suture procedure was performed to repair sports-related horizontal tears in the middle and posterior segments of the medial (11 cases) and lateral (2 cases) menisci in 13 patients (mean age: 30 ± 14 years). Pre- and post-operative Barrett criteria, Lysholm scores, and patient ability to resume sports were assessed. Magnetic resonance imaging (MRI) grades and signal intensity changes near the joint capsule were evaluated in the 9 cases among which pre- and post-operative MRI images were available.All Barrett criteria items were negative following surgery; Lysholm scores increased from 70.2 ± 13.1 before surgery to 98.9 ± 2.64 after surgery (P < .01). All patients were able to resume their sport. Preoperative MRI grade of tears was 3 for all patients; postoperative MRI grades were 1 in 3 cases, 2 in 4 cases, and 3 in 2 cases (P < .05). Importantly, MRI signal intensity at the repaired menisci near the joint capsule was reduced in 8 of these 9 cases postoperatively.The inter-leaf vertical suture procedure is associated with good outcomes for horizontal tears in the middle and posterior segments of the medial and lateral menisci. The procedure is useful and convenient.

Ramp lesions: a systematic review of MRI diagnostic accuracy and treatment efficacy

Purpose

We conducted a systematic review of the published literature to assess the accuracy of Magnetic Resonance Imaging (MRI) in establishing the presence of ramp lesions (RLs) in Anterior Cruciate Ligament (ACL) deficient knees and the clinical efficacy of the surgical repair of RLs.

Methods

A comprehensive search of the MEDLINE, Web of Science and Scopus databases was performed according to PRISMA guidelines. Studies assessing MRI diagnostic accuracy for RLs or the clinical effect of RL repair in participants with ACL injuries were included. Diagnostic accuracy measures were pooled and plotted in forest plots. Preoperative and at last follow-up treatment efficacy outcome measures were extracted and plotted in forest plots, for graphical comprehension.

Results

Sixteen studies met the criteria and were included. The diagnostic analysis showed a pooled sensitivity, specificity, positive and negative likelihood ratios of 65.1% (95% CI, 59.73 to 70.42), 91.6% (95% CI, 89.14 to 94.05), 2.91 (95% CI, 2.38–3.55) and 0.53 (95% CI, 0.44–0.64), respectively, with high heterogeneity (I² above 80%) for all measures. Treatment analysis showed improved Lysholm Knee Score, IKDC score and laxity difference between the knees in all studies after meniscal suture repair. A separate analysis showed no differences between repair of smaller, stable, RLs with meniscal sutures and repair with abrasion and trephination only.

Conclusion

Although the results present considerable heterogeneity, MRI seems to demonstrate moderate accuracy in the diagnosis of RLs in patients with ACL tear and the surgical repair of RLs can be associated with improved overall outcomes.

The measurement of medial knee gap width using ultrasound

INTRODUCTION

Medial knee instability is a key clinical parameter for assessing ligament injury and arthroplasty success, but current methods for measuring stability are typically either qualitative or involve ionizing radiation. The purpose of this study was to perform a preliminary analysis of whether ultrasound (US) could be used as an alternate approach for quantifying medial instability by comparing an US method with an approach mimicking the current gold standard fluoroscopy method.

MATERIALS AND METHODS

US data from the medial knee were collected, while cadaveric lower limbs (n = 8) were loaded in valgus (10 Nm). During post-processing, the US gap width was measured by identifying the medial edges of the femur and tibia and computing the gap width between these points. For comparison, mimicked fluoroscopy (mFluoro) images were created from specimen-specific bone models, developed from segmented CT scans, and from kinematic data collected during testing. Then, gap width was measured in the mFluoro images based on two different published approaches with gap width measured either at the most medial or at the most distal aspect of the femur.

RESULTS

Gap width increased significantly with loading (p < 0.001), and there were no significant differences between the US method (unloaded: 8.7 ± 2.4 mm, loaded: 10.7 ± 2.2 mm) and the mFluoro method that measured gap width at the medial femur. In terms of the change in gap width with load, no correlation with the change in abduction angle was observed, with no correlation between the various methods. Inter-rater reliability for the US method was high (0.899-0.952).

CONCLUSIONS

Ultrasound shows promise as a suitable alternative for quantifying medial instability without radiation exposure. However, the outstanding limitations of existing approaches and lack of true ground-truth data require that further validation work is necessary to better understand the clinical viability of an US approach for measuring medial knee gap width.

Clinical assessment of antero-medial rotational knee laxity: a systematic review

PURPOSE

To inventory the examination methods available to assess antero-medial rotational laxity (AMRL) of the knee following medial collateral ligament injury.

METHODS

Searches were conducted in accordance with the PRISMA guidelines and using four online databases: WEB OF SCIENCE, MEDLINE, EMBASE, and AMED. The Critical Appraisal Skills Programme guidelines for Diagnostic Test Studies were used for the quality assessment of the articles.

RESULTS

A total of 2241 articles were identified from the database searches. From this, four articles were included in the final review. All were case-control studies, considered a combined ACL/MCL injury and had small study populations. Specialised equipment was required in all studies, and one needed additional imaging support before measurements could be taken. Two employed commercially available measuring equipment as part of the assessment process.

CONCLUSION

Clinical assessment of AMRL in relation to a MCL injury remains challenging. Although methods have been developed to support clinical examination, they are limited by a number of factors, including the need for additional time in the clinical environment when setting up equipment, the need for specific equipment to produce and measure rotational movement and imaging support. In addition, there are patient safety concerns from the repeated imaging. A reliable and valid clinical examination remains to be found to truly assess antero-medial rotational laxity of the knee.

LEVEL OF EVIDENCE

IV.

Increased Medial Meniscal Slope Is Associated With Greater Risk of Ramp Lesion in Noncontact Anterior Cruciate Ligament Injury

BACKGROUND

A special type of meniscal lesion involving the peripheral attachment of the posterior horn of the medial meniscus (PHMM), termed ramp lesion, is commonly associated with anterior cruciate ligament (ACL) injury. However, no study has investigated its anatomic risk factors. Recently, increased meniscal slope has been identified as an independent anatomic risk factor for noncontact ACL injury.

HYPOTHESIS

Increased medial meniscal slope (MMS) as measured on magnetic resonance imaging (MRI) will correlate with greater risk of concomitant ramp lesion in noncontact ACL injury.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

From January 2011 to December 2013, a total of 1012 consecutive patients were diagnosed as having noncontact ACL injuries and underwent primary ACL reconstructions. Among them, 160 patients were arthroscopically verified to have concomitant ramp lesions. Study exclusion criteria included partial ACL rupture, multiligamentous injury, associated medial/lateral meniscal lesions other than ramp lesion, skeletal immaturity, general joint laxity, severe malalignment of the lower extremity, history of knee surgery, lack of available preoperative MRI, and history of trauma to the proximal tibia. This left 53 patients in the study group (ACL + ramp group), who were matched in a 1:1 fashion to 53 control participants (isolated ACL group) who were arthroscopically verified to have isolated complete ACL injury during the same study period. Patients were matched by age, sex, and time from injury to surgery (TFI). Patients from the matched control group were selected by applying the same exclusion criteria as mentioned above. The MMS and medial posterior tibial slope (MPTS) were measured on the preoperative MRI in a blinded fashion. Predictors of ramp lesion, including MMS, MPTS, body mass index, pivot-shift test grade, and KT-1000 arthrometer side-to-side difference, were assessed by multivariable conditional logistic regression analysis.

RESULTS

The mean MMS in the study group was 3.5°, which was significantly larger than that in the control group (2.0°; P < .001). In addition, increased MMS was significantly (odds ratio [OR], 5.180; 95% CI, 1.814-32.957; P < .001) associated with concomitant ramp lesion in noncontact ACL injury, especially for those with a TFI of ≥6 months (OR, 13.819; 95% CI, 2.251-49.585; P < .001). However, no significant association was identified between MPTS and concomitant ramp lesion.

CONCLUSION

Increased MMS was identified to be an independent anatomic risk factor of concomitant ramp lesions in noncontact ACL injuries, particularly for those with a TFI ≥6 months. This may provide additional information for counseling patients who have increased MMS on the greater risk of secondary PHMM lesions if their ACL-deficient knee joints are not well stabilized initially.

Vertical Tears of the Lateral Meniscus: Effects on In Vitro Tibiofemoral Joint Mechanics

BACKGROUND

Lateral meniscal tears are often seen with acute anterior cruciate ligament (ACL) injury and may be left in situ, repaired, or treated with meniscectomy. Clinical studies have shown good outcomes with vertical tears left in situ and poor outcomes following meniscectomy. However, clinically relevant studies are needed to establish a biomechanical foundation for treatment of these tears, particularly regarding the effects of meniscectomy.

PURPOSE

To compare tibiofemoral joint mechanics following vertical lateral meniscal tears and meniscectomies. We hypothesized that a peripheral vertical tear of the lateral meniscus would alter joint mechanics, increasing contact pressure and area, and that more drastic effects would be seen following meniscectomy, at higher knee flexion angles, and with increased loads.

STUDY DESIGN

Controlled laboratory study.

METHODS

Ten fresh-frozen cadaveric knees (average age, 55 ± 12 years) were tested with 5 lateral meniscus states: intact, short vertical tear, extended vertical tear, posterior horn partial meniscectomy (rim intact), and posterior horn subtotal meniscectomy (rim excised). The specimens were loaded axially at knee flexion angles of 0°, 30°, and 60°, and musculotendinous forces were applied, simulating a 2-legged squat. Intra-articular contact pressures were measured using pressure-sensitive Fuji film. Kinematic data were acquired through digitization of fiducial markers.

RESULTS

Vertical tears did not cause a significant change in contact pressure or area. Partial meniscectomy increased maximum contact pressures in the lateral compartment at 30° and 60° from 5.3 MPa to 7.2 MPa and 7.6 MPa, respectively (P = .02, P = .007). Subtotal meniscectomy (8.4 MPa) significantly increased contact pressure compared with partial meniscectomy (7.6 MPa) at 60° (P = .04). Both meniscectomy states significantly increased contact pressures with increasing flexion from 0° to 60° (P < .001, P < .001).

CONCLUSION

Vertical tears of the lateral meniscus during a simulated 2-legged squat did not significantly change contact pressures and areas compared with an intact meniscus. However, treating these tears with partial and complete meniscectomy significantly increased maximum contact pressures.

CLINICAL RELEVANCE

Biomechanical evidence supports treating vertical lateral meniscus tears with meniscal-sparing techniques as opposed to meniscectomy, which may lead to progressive degenerative joint disease from altered joint biomechanics.

Clinical biomechanics of instability related to total knee arthroplasty

BACKGROUND

Tibiofemoral instability is a common reason for total knee arthroplasty failure, and may be attributed to soft tissue deficiency and incorrect ligament balancing. There are many different designs of implant with varying levels of constraint to overcome this instability; however there is little advice for surgeons to assess which is suitable for a specific patient, and soft tissue balance testing during arthroplasty is very subjective.

METHOD

The current theories on primary and secondary soft tissue restraints to anterior/posterior, varus/valgus, and internal/external rotational motion of the knee are discussed. The paper reviews biomechanics literature to evaluate instability in the intact and implanted knee.

FINDINGS

The paper highlights important intra- and extra-capsular structures in the knee and describes the techniques used by clinicians to assess instability perioperatively. In vitro cadaveric studies were found to be a very useful tool in comparing different implants and contributions of different soft tissues.

INTERPRETATION

In vitro cadaveric studies can be utilised in helping less experienced surgeons with soft tissue releases and determining the correct implant. For this to happen, more biomechanical studies must be done to show the impact of release sequences on implanted cadavers, as well as determining if increasingly constrained implants restore the stability of the knee to pre-deficient conditions.

Effect of partial medial meniscectomy on anterior tibial translation in stable knees: a prospective controlled study on 32 patients

BACKGROUND

Quantitative measurement of anterior translation of the tibia (ATT) by KT 1000 is used mainly to provide an objective assessment of knee laxity after anterior cruciate ligament (ACL) tears or ACL reconstructions. Only few papers described its use after menisectomies in knees with intact ACL. The objective of this paper is to determine whether partial medial meniscectomies could induce significant immediate post-operative ATT.

METHODS

Thirty-two patients with a diagnosis of partial medial meniscal tear limited to the posterior horn and documented with magnetic resonance imaging (MRI) were assessed under anesthesia before and immediately after arthroscopic meniscectomy. The assessment was performed by the same examiner by means of the MEDmetric(R) KT-1000 instrument using manual maximum (MM) force. The opposite knees were also assessed.

RESULTS

There is a significant difference between pre and post-operative KT MM mean values for the operated knees (CI: -3.933953 to -2.947297, p < 0.0001). No significance was found between the mean values for the contralateral knees before and after the completion of the menisectomy on the operated knees (p = 0.4). For the operated knees, 14 (43.75%) had a side-to-side difference between pre-and post-operative values of more than 3 mm, whereas for the contralateral knees, only 2 (6%) had the same.

CONCLUSION

Less than half of operated knees showed significant side-to-side difference values of ATT (>3 mm), immediately after meniscectomies in unconscious patients. Our values might reflect a temporarily increase of anterior laxity under specific conditions but whether a significant laxity remains in some knees, such changes may lead to higher cartilage loading and early osteoarthritis.

Effect of timing of ACL reconstruction in surgery and development of meniscal and chondral lesions

PURPOSE

To investigate whether a delay in the timing of surgery of > 6 months compared with performing the surgery ≤ 6 months after the anterior cruciate ligament (ACL) injury leads to an increased risk of injuries or degenerative changes in the ACL-deficient knee.

METHODS

Patients who underwent primary ACL reconstruction at an academic tertiary care center, and had preoperative magnetic resonance imaging (MRI) performed within 2 months of the time of the ACL injury were included. The prevalence of degenerative changes at the time of surgery was assessed and related to the timing of ACL surgery, with "early reconstruction" defined as a surgery performed ≤ 6 months and "delayed reconstruction" defined as surgery performed > 6 months after ACL injury. "New" meniscal tears were defined as lesions detected at the time of surgery that were not detected by MRI.

RESULTS

Of 195 patients who were selected based on inclusion criteria, 171 patients underwent surgery ≤ 6 months after their ACL injury, and 24 patients underwent surgery > 6 months after their ACL injury. The prevalence of new medial meniscal tears in the early reconstruction group was 4.1%, while in the delayed reconstruction group, the prevalence was 16.7% (P = 0.012).

CONCLUSION

A delay in the timing of ACL reconstruction from ≤ 6 months to > 6 months following injury is associated with a significant increase in the prevalence of medial meniscal tears (P = 0.012), with a relative risk of 4.07 (CI, 1.29-12.88).

Medial meniscal tears in anterior cruciate ligament-deficient knees: effects of posterior tibial slope on medial meniscal tear

Purpose

To evaluate the incidence of meniscal tears in patients with chronic anterior cruciate ligament (ACL)-deficient knees, and to determine the influence of posterior tibial slope (PTS) on medial meniscal tears in ACL-deficient knees.

Materials and Methods

We reviewed 174 patients (174 knees) with a mean age of 30.7 years who underwent ACL reconstruction for chronic ACL tears. We divided the patients into two groups: low group (135 knees with a PTS<13°) and high group (39 knees with a PTS≥13°).

Results

The incidence of medial meniscus tears was 44% (77/174), and that of lateral meniscus tears was 35% (61/174). The mean PTS in patients with medial meniscal tears was 11.4°±3.0°, whereas that in patients without medial meniscal tears was 9.8°±2.4°. The incidence of meniscal tears was 57.8% (78/135) in the low group and 89.7% (35/39) in the high group (p<0.001).

Conclusions

Our data demonstrate that PTS≥13° is a risk factor for secondary medial meniscal tears in ACL-deficient knees. So, we suggest that PTS is one of the considerations for determining early ACL reconstruction to prevent secondary meniscal tears.

Longitudinal tear of the medial meniscus posterior horn in the anterior cruciate ligament-deficient knee significantly influences anterior stability

BACKGROUND

Longitudinal tears of the medial meniscus posterior horn (MMPH) are commonly associated with a chronic anterior cruciate ligament (ACL) deficiency. Many studies have demonstrated the importance of the medial meniscus in terms of limiting the amount of anterior-posterior tibial translation in response to anterior tibial loads in ACL-deficient knees.

HYPOTHESIS

An MMPH tear in an ACL-deficient knee increases the anterior-posterior tibial translation and rotatory instability. In addition, MMPH repair will restore the tibial translation to the level before the tear.

STUDY DESIGN

Controlled laboratory study.

METHODS

Ten human cadaveric knees were tested sequentially using a custom testing system under 5 conditions: intact, ACL deficient, ACL deficient with an MMPH peripheral longitudinal tear, ACL deficient with an MMPH repair, and ACL deficient with a total medial meniscectomy. The knee kinematics were measured at 0°, 15°, 30°, 60°, and 90° of flexion in response to a 134-N anterior and 200-N axial compressive tibial load. The rotatory kinematics were also measured at 15° and 30° of flexion in a combined rotatory load of 5 N·m of internal tibial torque and 10 N·m of valgus torque.

RESULTS

Medial meniscus posterior horn longitudinal tears in ACL-deficient knees resulted in a significant increase in anterior-posterior tibial translation at all flexion angles except 90° (P < .05). An MMPH repair in an ACL-deficient knee showed a significant decrease in anterior-posterior tibial translation at all flexion angles except 60° compared with the ACL-deficient/MMPH tear state (P < .05). The total anterior-posterior translation of the ACL-deficient/MMPH repaired knee was not significantly increased compared with the ACL (only)-deficient knee but was increased compared with the ACL-intact knee (P > .05). A total medial meniscectomy in an ACL-deficient knee did not increase the anterior-posterior tibial translation significantly compared with MMPH tears in ACL-deficient knees at all flexion angles (P > .05). In a combined rotatory load, tibial rotation after MMPH tears or a total medial meniscectomy in an ACL-deficient knee were not affected significantly at all flexion angles.

CONCLUSION

This study shows that an MMPH longitudinal tear in an ACL-deficient knee alters the knee kinematics, particularly the anterior-posterior tibial translation. MMPH repair significantly improved anterior-posterior tibial translation in ACL-deficient knees.

CLINICAL RELEVANCE

These findings may help improve the treatment of patients with ACL and MMPH longitudinal tear by suggesting that the medial meniscal repairs should be performed for greater longevity when combined with an ACL reconstruction.

Management of medial-sided knee injuries, part 1: medial collateral ligament

The medial collateral ligament complex is a primary stabilizer that combines static and dynamic resistance to direct valgus stress while contributing significant restraints to rotatory motion and anterior-posterior translation. Varying opinions exist among investigators regarding injury classification and treatment algorithms. Whereas most agree that the majority of isolated medial collateral ligament complex injuries can be treated nonoperatively, isolated injuries with chronic instability and multiligament injuries may require operative intervention. Substantial confounding factors are present within published reports, making comparative analyses and systematic review challenging. This review focuses on the anatomy and biomechanics of the medial structures of the knee; it discusses the clinical evaluation of complex injuries; and it reviews nonoperative and operative treatment methods.

Arthroscopic prevalence of ramp lesion in 868 patients with anterior cruciate ligament injury

BACKGROUND

A special type of repairable meniscal lesion involving the peripheral attachment of the posterior horn of the medial meniscus is commonly associated with anterior cruciate ligament deficiency and is termed a "ramp lesion." However, there are no previously published articles reporting the epidemiologic characteristics of ramp lesions.

HYPOTHESIS

The ramp lesion is a special type of medial meniscal tear with high prevalence associated with anterior cruciate ligament rupture; the prevalence increases with time from anterior cruciate ligament injury. Age and gender are risk factors affecting the prevalence of the ramp lesion.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

From April 2002 to October 2007, 868 consecutive knees were diagnosed as having an anterior cruciate ligament injury and received arthroscopic surgery for anterior cruciate ligament reconstruction. All the patients had verified tears of the ramp area under arthroscopy. The prevalence of the ramp lesion was evaluated retrospectively. Then, all cases were divided into different groups depending on the time interval from anterior cruciate ligament injury to anterior cruciate ligament reconstruction and other relevant risk factors such as age and gender. The effects of age, gender, and time from injury on the prevalence of ramp lesions were analyzed.

RESULTS

Among 868 knees that underwent surgery for anterior cruciate ligament reconstruction, 144 knees were diagnosed as having a ramp lesion. The mean age was 24.7 years; there were 113 male and 31 female patients. The mean time from injury to anterior cruciate ligament reconstruction was 27.2 months. The prevalence of ramp lesions was 16.6%, which was analyzed as a logarithmic correlation with time from injury. Patients younger than 30 years of age and male patients had a significantly higher prevalence of ramp lesions.

CONCLUSION

The ramp lesion is a common meniscal injury that can occur at the time of anterior cruciate ligament rupture or as a result of knee laxity associated with anterior cruciate ligament insufficiency. The prevalence of ramp lesion in this patient group was 16.6%, which increased with time until 24 months after initial injury. Patients younger than 30 years of age and male patients had a higher prevalence of ramp lesions.

Estimation of ligament loading and anterior tibial translation in healthy and ACL-deficient knees during gait and the influence of increasing tibial slope using EMG-driven approach

The purpose of this study was to develop a biomechanical model to estimate anterior tibial translation (ATT), anterior shear forces, and ligament loading in the healthy and anterior cruciate ligament (ACL)-deficient knee joint during gait. This model used electromyography (EMG), joint position, and force plate data as inputs to calculate ligament loading during stance phase. First, an EMG-driven model was used to calculate forces for the major muscles crossing the knee joint. The calculated muscle forces were used as inputs to a knee model that incorporated a knee–ligament model in order to solve for ATT and ligament forces. The model took advantage of using EMGs as inputs, and could account for the abnormal muscle activation patterns of ACL-deficient gait. We validated our model by comparing the calculated results with previous in vitro, in vivo, and numerical studies of healthy and ACL-deficient knees, and this gave us confidence on the accuracy of our model calculations. Our model predicted that ATT increased throughout stance phase for the ACL-deficient knee compared with the healthy knee. The medial collateral ligament functioned as the main passive restraint to anterior shear force in the ACL-deficient knee. Although strong co-contraction of knee flexors was found to help restrain ATT in the ACL-deficient knee, it did not counteract the effect of ACL rupture. Posterior inclination angle of the tibial plateau was found to be a crucial parameter in determining knee mechanics, and increasing the tibial slope inclination in our model would increase the resulting ATT and ligament forces in both healthy and ACL-deficient knees.

Tibiofemoral joint positioning for the valgus stress test

CONTEXT

Recommendations on the positioning of the tibiofemoral joint during a valgus stress test to optimize isolation of the medial collateral ligament (MCL) from other medial joint structures vary in the literature. If a specific amount of flexion could be identified as optimally isolating the MCL, teaching and using the technique would be more consistent in clinical application.

OBJECTIVE

To determine the angle of tibiofemoral joint flexion between 0 degrees and 20 degrees that causes a difference in the slope of the force-strain line when measuring the resistance to a valgus force applied to the joint.

DESIGN

Cross-sectional study.

SETTING

University research laboratory.

PATIENTS OR OTHER PARTICIPANTS

Twelve healthy volunteers (6 men, 6 women: age = 26.4 +/- 5.6 years, height = 170.9 +/- 8.4 cm, mass = 75.01 +/- 14.6 kg).

INTERVENTION(S)

Using an arthrometer, we applied a valgus force, over a range of 60 N, to the tibiofemoral joint in 0 degrees , 5 degrees , 10 degrees , 15 degrees , and 20 degrees of flexion.

MAIN OUTCOME MEASURE(S)

Force-strain measurements were obtained for 5 positions of tibiofemoral joint flexion.

RESULTS

As knee flexion angle increased, slope values decreased (F(4,44) = 17.6, P < .001). The slope at full extension was not different from that at 5 degrees of flexion, but it was different from the slopes at angles greater than 10 degrees of flexion. Similarly, the slope at 5 degrees of flexion was not different from that at 10 degrees of flexion, but it was different from the slopes at 15 degrees and 20 degrees of flexion. Further, the slope at 10 degrees of flexion was not different from that at 15 degrees or 20 degrees of flexion. Finally, the slope at 15 degrees of flexion was not different from that at 20 degrees of flexion.

CONCLUSIONS

When performing the manual valgus stress test, the clinician should fully extend the tibiofemoral joint or flex it to 5 degrees to assess all resisting medial tibiofemoral joint structures and again at 15 degrees to 20 degrees of joint flexion to further assess the MCL.

Biomechanical evaluation of using one hamstrings tendon for ACL reconstruction: a human cadaveric study

Harvesting both the semitendinosus and gracilis tendons for anterior cruciate ligament (ACL) reconstruction has a negative impact on muscle strength as well as knee function and stability. With a new "All-inside" technique, using only one hamstrings tendon (semitendinosus or gracilis) is possible because of a reduction in length requirements. The research question of this in vitro study was whether the use of only one hamstrings tendon (semitendinosus or gracilis) could restore knee kinematics and in situ force in the ACL to the level of an intact knee.Ten human cadaveric knees were tested in the following conditions: (1) intact, (2) ACL-deficient, and (3) ACL reconstruction with the "All-inside" technique using the (a) single semitendinosus tendon graft, or (b) single gracilis tendon graft. Using a robotic testing system, external loads, i.e. (1) an anterior tibial load of 134-N and (2) combined rotatory loads of 10-Nm valgus and 5-Nm internal tibial torques, were applied. The multiple degrees of freedom knee kinematics and the in situ forces in the ACL and ACL grafts were determined. In response to a 134-N anterior tibial load, the use of either graft could restore anterior tibial translation to within 1.3 mm of the intact knee. The in situ forces in the two grafts were not significantly different from those of the intact ACL. Under the combined rotatory loads, both grafts could restore knee kinematics as well as the in situ force in the grafts to the level of the intact ACL. The "All-inside" technique using either the semitendinosus or gracilis tendon for ACL reconstruction could satisfactorily restore time-zero knee kinematics and the in situ forces in either graft to those for the intact ACL, supporting clinical findings.

Tibiofemoral contact mechanics with a femoral resurfacing prosthesis and a non-functional meniscus

BACKGROUND

Increased contact stress with a femoral resurfacing prosthesis implanted in the medial femoral condyle and a non-functional meniscus is of concern for potential deleterious effects on tibiofemoral contact mechanics.

METHODS

Peak contact pressures were determined in seven fresh frozen human cadaveric specimens using a pressure sensitive sensor placed in the medial compartment above the menisci. A knee simulator was used to test each knee in static stance positions (5 degrees/15 degrees/30 degrees/45 degrees) and through 10 dynamic knee flexion cycles (5-45 degrees) with single body weight ground reaction force which was adjusted to the living body weight of the cadaver donor. All specimens were tested in three different conditions: untreated knee (A); flush implantation of a 20mm resurfacing prosthesis (HemiCAP) in the weight bearing area of the medial femoral condyle (B); complete radial tear at the posterior horn of the medial meniscus with the femoral resurfacing device in place (C).

FINDINGS

On average, flush device implantation resulted in no statistically significant differences when compared to the untreated normal knee. The meniscal tear resulted in a significant increase of the mean maximum peak contact pressures by 63%, 57%, and 57% (all P< or =0.05) at 15 degrees , 30 degrees and 45 degrees static stance positions and 78% (P< or =0.05) through the dynamic knee flexion cycle. No significant different maximum peak contact pressures were observed at 5 degrees stance position.

INTERPRETATION

Although the condition of a meniscal tear without the resurfacing device could not be compared, possible effects of reduced meniscal tissue and biomechanical integrity of the meniscus must be considered in an in vivo application.

Novel measurement technique of the tibial slope on conventional MRI

The posterior inclination of the tibial plateau, which is referred to as posterior tibial slope, is determined routinely on lateral radiographs. However, radiographically, it is not always possible to reliably recognize the lateral plateau, making a separate assessment of the medial and lateral plateaus difficult. We propose a technique to measure the plateaus separately by defining a tibial longitudinal axis on a conventional MRI. The medial plateau posterior tibial slope obtained from radiographs was compared with MR images in 100 consecutive patients with knee pain when ligament or meniscal injury was assumed. The posterior tibial slope on MRI correlated with those on radiographs. The mean posterior tibial slope was 3.4 degrees smaller on MRI compared with radiographs (4.8 degrees +/- 2.4 degrees versus 8.2 degrees +/- 2.8 degrees , respectively). The reproducibility was slightly better on radiographs than MRI (+/- 0.9 degrees versus +/- 1.4 degrees ). Twenty-one of the 100 cases had more than a 5 degrees difference (range, -8.7 degrees to 8.9 degrees ) between the medial and lateral plateaus. The proposed technique allows measurement of the posterior tibial slope of the medial and lateral plateaus on a standard knee MRI. By using this novel measurement technique, a reliable assessment of the medial and lateral tibial plateaus is possible.

LEVEL OF EVIDENCE

Level III, diagnostic study. See the Guidelines for Authors for a complete description of levels of evidence.

Biomechanical comparison of medial collateral ligament reconstructions using computer-assisted navigation

BACKGROUND

The medial collateral ligament is a broad ligament that functions as the primary stabilizer against valgus knee stress, particularly at 30 degrees of flexion.

HYPOTHESIS

A double-bundle reconstruction technique that better restores the native medial collateral ligament anatomy will restore valgus and external rotation stability to a medial collateral ligament-deficient knee.

STUDY DESIGN

Controlled laboratory study.

METHODS

Seven fresh-frozen cadaveric knees were studied. A surgical navigation system was used to determine valgus opening and external rotation at 0 degrees and 30 degrees with a 9.8-N.m valgus stress applied to the tibia graft isometry at multiple points on the tibia and femur. Intact and disrupted medial collateral ligament knees were used as controls. Four repair techniques were tested: Bosworth, modified Bosworth, anatomical single bundle, and anatomical double bundle.

RESULTS

Complete sectioning of the medial collateral ligament resulted in an increase in valgus opening of 5 degrees at 0 degrees and 7.7 degrees at 30 degrees . External rotation increased 4.6 degrees at 0 degrees and 9.7 degrees at 30 degrees . Single-bundle techniques (Bosworth, anatomical single bundle) did not restore valgus laxity at 0 degrees or 30 degrees ; the anatomical single bundle did not restore external rotation at 0 degrees . Double-bundle techniques (modified Bosworth, anatomical double bundle) restored valgus laxity and external rotation to the native knee conditions at 0 degrees and 30 degrees . At 30 degrees , the modified Bosworth was 0.3 degrees tighter and the anatomical double bundle 0.2 degrees tighter than was the intact knee. The center of the medial collateral ligament origin on the femur to the proximal insertion of the superficial medial collateral ligament resulted in the most isometric graft position.

CONCLUSION

Medial collateral ligament reconstruction configurations that use a double-bundle reconstruction better resist valgus and external rotations in response to valgus stress than do single-bundle techniques.

CLINICAL RELEVANCE

Although the medial collateral ligament often heals without surgical intervention, surgical reconstruction is occasionally necessary in grade III medial collateral ligament and combined ligamentous injuries to the knee. Double-bundle reconstruction of the medial collateral ligament better resists valgus forces across the knee and may allow for better surgical outcome after medial collateral ligament reconstruction.

Role of biomechanics in the understanding of normal, injured, and healing ligaments and tendons

Ligaments and tendons are soft connective tissues which serve essential roles for biomechanical function of the musculoskeletal system by stabilizing and guiding the motion of diarthrodial joints. Nevertheless, these tissues are frequently injured due to repetition and overuse as well as quick cutting motions that involve acceleration and deceleration. These injuries often upset this balance between mobility and stability of the joint which causes damage to other soft tissues manifested as pain and other morbidity, such as osteoarthritis.

The healing of ligament and tendon injuries varies from tissue to tissue. Tendinopathies are ubiquitous and can take up to 12 months for the pain to subside before one could return to normal activity. A ruptured medial collateral ligament (MCL) can generally heal spontaneously; however, its remodeling process takes years and its biomechanical properties remain inferior when compared to the normal MCL. It is also known that a midsubstance anterior cruciate ligament (ACL) tear has limited healing capability, and reconstruction by soft tissue grafts has been regularly performed to regain knee function. However, long term follow-up studies have revealed that 20–25% of patients experience unsatisfactory results. Thus, a better understanding of the function of ligaments and tendons, together with knowledge on their healing potential, may help investigators to develop novel strategies to accelerate and improve the healing process of ligaments and tendons.

With thousands of new papers published in the last ten years that involve biomechanics of ligaments and tendons, there is an increasing appreciation of this subject area. Such attention has positively impacted clinical practice. On the other hand, biomechanical data are complex in nature, and there is a danger of misinterpreting them. Thus, in these review, we will provide the readers with a brief overview of ligaments and tendons and refer them to appropriate methodologies used to obtain their biomechanical properties. Specifically, we hope the reader will pay attention to how the properties of these tissues can be altered due to various experimental and biologic factors. Following this background material, we will present how biomechanics can be applied to gain an understanding of the mechanisms as well as clinical management of various ligament and tendon ailments. To conclude, new technology, including imaging and robotics as well as functional tissue engineering, that could form novel treatment strategies to enhance healing of ligament and tendon are presented.

Medial collateral ligament injuries and subsequent load on the anterior cruciate ligament: a biomechanical evaluation in a cadaveric model

BACKGROUND

Numerous studies have documented the effect of complete medial collateral ligament injury on anterior cruciate ligament loads; few have addressed how partial medial collateral ligament disruption affects knee kinematics.

PURPOSE

To determine knee kinematics and subsequent change in anterior cruciate ligament load in a partial and complete medial collateral ligament injury model.

STUDY DESIGN

Controlled laboratory study.

METHODS

Ten human cadaveric knees were sequentially tested by a robot with the medial collateral ligament intact, in a partial injury model, and in a complete injury model with a universal force-moment sensor measuring system. Tibial translation, rotation, and anterior cruciate ligament load were measured under 3 conditions: anterior load (125 N), valgus load (10 N x m), and internal-external rotation torque (4 N x m; all at 0 degrees and 30 degrees of flexion).

RESULTS

Anterior and posterior translation did not statistically increase with a partial or complete medial collateral ligament injury at 0 degrees and 30 degrees of flexion. In response to a 125 N anterior load, at 0 degrees , the anterior cruciate ligament load increased 8.7% (from 99.5 to 108.2 N; P = .006) in the partial injury and 18.3% (117.7 N; P < .001) in the complete injury; at 30 degrees , anterior cruciate ligament load was increased 12.3% (from 101.7 to 114.2 N; P = .001) in the partial injury and 20.6% (122.7 N; P < .001) in the complete injury. In response to valgus torque (10 N x m) at 30 degrees , anterior cruciate ligament load was increased 55.3% (30.4 to 47.2 N; P = .044) in the partial injury model and 185% (86.8 N; P = .001) in the complete injury model. In response to internal rotation torque (4 N.m) at 30 degrees , anterior cruciate ligament load was increased 29.3% (27.6 to 35.7 N; P = .001) in the partial injury model and 65.2% (45.6 N; P < .001) in the complete injury model. The amount of internal rotation at 30 degrees of flexion was significantly increased in the complete injury model (22.8 degrees ) versus the intact state (19.5 degrees ; P < .001).

CONCLUSION

Partial and complete medial collateral ligament tears significantly increased the load on the anterior cruciate ligament. In a partial tear, the resultant load on the anterior cruciate ligament was increased at 30 degrees of flexion and with valgus load and internal rotation torque.

CLINICAL RELEVANCE

Patients may need to be protected from valgus and internal rotation forces after anterior cruciate ligament reconstruction in the setting of a concomitant partial medial collateral ligament tear. This information may help clinicians understand the importance of partial injuries of the medial collateral ligament with a combined anterior cruciate ligament injury complex.

Force measurements on the posterior oblique ligament and superficial medial collateral ligament proximal and distal divisions to applied loads

BACKGROUND

There is limited information regarding load responses of the posterior oblique and superficial medial collateral ligaments to applied loads.

HYPOTHESES

The degree of knee flexion affects loads experienced by the posterior oblique ligament and both divisions of the superficial medial collateral ligament. The posterior oblique ligament provides significant resistance to valgus and internal rotation forces near knee extension. Different load responses are experienced by proximal and distal divisions of the superficial medial collateral ligament.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Twenty-four nonpaired, fresh-frozen cadaveric knees were tested. Buckle transducers were applied to the proximal and distal divisions of the superficial medial collateral and posterior oblique ligaments. Applied loads at 0 degrees, 20 degrees, 30 degrees, 60 degrees, and 90 degrees of knee flexion consisted of 10 N m valgus loads, 5 N.m internal and external rotation torques, and 88 N anterior and posterior drawer loads.

RESULTS

External rotation torques produced a significantly higher load response on the distal superficial medial collateral ligament than did internal rotation torques at all flexion angles with the largest difference at 90 degrees (96.6 vs 22.5 N). For an applied valgus load at 60 degrees of knee flexion, loads on the superficial medial collateral ligament were significantly higher in the distal division (103.5 N) than the proximal division (71.9 N). The valgus load response of the posterior oblique ligament at 0 degrees of flexion (19.1 N) was significantly higher than at 30 degrees (10.6 N), 60 degrees (7.8 N), and 90 degrees (6.8 N) of flexion. At 0 degrees of knee flexion, the load response to internal rotation on the posterior oblique ligament (45.8 N) was significantly larger than was the response on both divisions of the superficial medial collateral ligament (20 N for both divisions). At 90 degrees of flexion, the load response to internal rotation torques reciprocated between these structures with a significantly higher response in the distal superficial medial collateral ligament division (22.5 N) than the posterior oblique ligament (9.1 N).

CONCLUSION

The superficial medial collateral ligament experienced the largest load response to applied valgus and external rotation torques; the posterior oblique ligament observed the highest load response to internal rotation near extension.

CLINICAL RELEVANCE

This study provides new knowledge of the individual biomechanical function of the main medial knee structures in an intact knee and will assist in the interpretation of clinical knee motion testing and provide evidence for techniques involving repair or reconstruction of the posterior oblique ligament and both divisions of the superficial medial collateral ligament.

A clinically relevant assessment of posterior cruciate ligament and posterolateral corner injuries. Evaluation of isolated and combined deficiency

BACKGROUND

The treatment of symptomatic posterior cruciate ligament injuries of the knee is controversial. Identification of concomitant injuries of the posterolateral corner is important to optimize surgical and clinical outcomes, although this diagnosis is sometimes difficult. The purpose of this study was to determine the physical examination and stress radiography parameters of isolated injuries of the posterior cruciate ligament and combined injuries of the posterior cruciate ligament and posterolateral corner. Our hypothesis was that Grade-3 posterior drawer laxity is an indicator of a concomitant injury of the posterolateral corner.

METHODS

Ten pairs of cadaver knees (a total of twenty knees) were evaluated with posterior drawer testing, dial testing, and stress radiography. Stress radiography was performed by applying a 200-N posterior drawer at 90 degrees of knee flexion. The knees were tested while intact and then retested following the sequential resection of the posterior cruciate ligament followed by the posterolateral corner structures.

RESULTS

All intact specimens were rated as Grade 0 on posterior drawer testing. Sectioning of the posterior cruciate ligament resulted in Grade-2 posterior drawer in all specimens. The additional resection of the posterolateral corner resulted in Grade-3 posterior drawer in all specimens. Dial testing of the intact knees resulted in a mean (and standard error) of 10.5 degrees +/- 1.0 degrees and 10.5 degrees +/- 0.80 degrees of external rotation at 30 degrees and 90 degrees, respectively. This increased significantly to 15.1 degrees +/- 1.1 degrees and 16.2 degrees +/- 0.89 degrees, respectively, following sectioning of the posterior cruciate ligament (p < 0.05). After resection of the posterolateral corner, rotation was further increased to a mean of 21.6 degrees +/- 1.5 degrees at 30 degrees and 27.5 degrees +/- 1.6 degrees at 90 degrees (p < 0.05). On stress radiography, the average posterior displacements measured 2.9 +/- 0.5 mm in the intact specimens, 12.7 +/- 1.0 mm after resection of the posterior cruciate ligament, and 22.3 +/- 1.6 mm after the additional resection of the posterolateral corner (p < 0.05). The corrected posterior displacement, calculated by subtracting the displacement in the intact knees, was 9.8 mm after resection of the posterior cruciate ligament and 19.4 mm after the additional resection of the posterolateral corner.

CONCLUSIONS

A grade of 3 on posterior drawer testing and >10 mm of posterior tibial translation on stress radiography correlate with the presence of a posterolateral corner injury in addition to a complete disruption of the posterior cruciate ligament.

Bilateral medial tibiofemoral joint stiffness in full extension and 20 degrees of knee flexion

CONTEXT

The valgus stress test is used clinically to assess injury to the medial knee structures in 2 positions: full extension and some degree of flexion. The amount of flexion used to "isolate" the medial collateral ligament is not consistent in the literature, but most studies have shown that stiffness of the ligaments was consistent between the limbs.

OBJECTIVE

To determine (1) if the stiffness of the medial knee structures was the same bilaterally, and (2) if the stiffness was different in full extension compared with 20 degrees of knee flexion.

DESIGN

Criterion standard, before-after design.

SETTING

University research laboratory.

PATIENTS OR OTHER PARTICIPANTS

Both knees of 45 healthy and active volunteers (26 females, 19 males; age = 23.2 +/- 3.96 years, height = 170.6 +/- 7.75 cm, mass = 74.2 +/- 15.14 kg) were studied.

INTERVENTION(S)

A valgus force of 60 N was applied to the lateral aspect of both knees in full extension and in 20 degrees of flexion.

MAIN OUTCOME MEASURE(S)

The slope of the force-strain line of the medial knee during a valgus force was calculated using the LigMaster arthrometer.

RESULTS

Slope means in full extension were 16.1 +/- 3.3 (right knee) and 15.8 +/- 3.1(left knee). Means for 20 degrees of flexion were 12.2 +/- 3.1 (right) and 11.7 +/- 2.8 (left). Stiffness was greater when the knee was in full extension versus 20 degrees of flexion (t(44) = 12.04, P < .001). No difference was noted between the slopes of the 2 knees in extension (t(44) = 0.74, P = .46) or in flexion (t(44) = 1.2, P = .27).

CONCLUSIONS

These findings support the use of the contralateral knee as a control. Further, the valgus stress test should be performed in full extension and in some degree of flexion to assess the different restraining structures of the medial tibiofemoral joint.

Influence of anterior cruciate ligament bundles on knee kinematics: clinical assessment using computer-assisted navigation

BACKGROUND

The synergistic functions of the anteromedial and posterolateral bundles of the anterior cruciate ligament in restraining anterior laxity are known. Cadaveric experiments have also suggested different functions of the 2 bundles in controlling a combined rotatory load simulating the pivot shift.

HYPOTHESIS

The posterolateral bundle is important in controlling the coupled tibial axial rotation laxity occurring during clinical laxity tests performed in vivo, particularly the pivot-shift maneuver.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

Twenty-one patients underwent navigated 2-bundle anterior cruciate ligament reconstruction. The navigation was additionally used to measure the knee kinematics in response to the anterior drawer test (performed at 90 degrees ), Lachman test (performed at 20 degrees of flexion), and pivot-shift test. Two sequential reconstruction protocols were used to assess the contribution of the anteromedial and posterolateral bundles to restraining tibial translations and coupled axial rotation occurring with the manually performed clinical laxity tests.

RESULTS

Anterior tibial translation during the anterior drawer test was better restrained by anteromedial bundle reconstruction than by posterolateral bundle reconstruction. Conversely, posterolateral bundle reconstruction better restrained anterior tibial translation during the Lachman test. Both bundles contributed to the control of anterior laxity during the pivot shift. However, the posterolateral bundle was more important than was the anteromedial bundle in controlling the tibial rotational component (posterolateral bundle reconstruction caused a 53% reduction in tibial rotation laxity compared with a 42% reduction with anteromedial bundle reconstruction, P< .0001).

CONCLUSION

This study provides objective, in vivo data about how the anteromedial and posterolateral bundles act differentially to stabilize the knee, particularly during the pivot shift. The posterolateral bundle was important in controlling not only anterior laxity toward knee extension but the rotational component of the pivot shift.

Computer evaluation of kinematics of anterior cruciate ligament reconstructions

Current clinical and instrumented outcome measurements of knee instability lack accuracy, especially when multiplanar instability is considered. The aim of our cadaveric study was to describe the kinematics in the intact, double bundle, and anteromedial bundle reconstructed anterior cruciate ligament knee by applying a protocol for computer-assisted evaluation of knee kinematics. An optical navigation system was used to acquire knee motion (n = 5) during clinical evaluations by tracking markers rigidly attached to the bones. The protocol included acquisition of anteroposterior translations and internal-external rotations and evaluation of three clinical knee laxity tests (anterior drawer, manual, and instrumented Lachman). Our anteroposterior translation data showed the double-bundle technique and anteromedial bundle technique could restore anteroposterior stability comparable to the intact state. For internal-external laxity, the double-bundle technique demonstrated overcorrection at 15 degrees, 60 degrees, 75 degrees, and 90 degrees. The anterior drawer and manual Lachman knee laxity tests showed improved stability for the double-bundle compared to the anteromedial bundle technique. This pilot study suggests the computation of knee laxity with a high precision method might be a step toward a more precise kinematic test of knee stability for evaluating different reconstruction methods.

Determination of a safe range of knee flexion angles for fixation of the grafts in double-bundle anterior cruciate ligament reconstruction: a human cadaveric study

BACKGROUND

For anterior cruciate ligament reconstruction with a double-bundle procedure, one of the major concerns is to not predispose either one of the grafts to risk of failure by overloading.

HYPOTHESIS

Knee flexion angles between 15 degrees and 45 degrees for anteromedial graft fixation and 15 degrees for posterolateral graft fixation are safe for both grafts in double-bundle anterior cruciate ligament reconstruction.

STUDY DESIGN

Controlled laboratory study.

METHODS

Nine human cadaveric knees were tested. The double-bundle anterior cruciate ligament reconstruction was conducted with both grafts fixed at 15 degrees of knee flexion (fixation protocol 15/15) and again with the anteromedial and posterolateral grafts fixed at 45 degrees and 15 degrees of knee flexion (fixation protocol 45/15). For both fixation protocols, the knee kinematics and the in situ forces of the reconstructed anterior cruciate ligament and its individual grafts were measured and collected under an anterior tibial load of 134 N and combined rotatory loads of 10 N.m of valgus and 5 N.m of internal tibial torque. The data from both fixation protocols were compared with those of an intact knee.

RESULTS

In response to the 2 external loading conditions, both fixation protocols (15/15 and 45/15) could restore the knee kinematics to within 2 mm of the intact knee (although statistically significant differences were found between fixation protocol 15/15 and the intact knee) and the overall in situ forces in the grafts similar to the intact anterior cruciate ligament. In response to the 134-N anterior tibial load, the in situ forces in the anteromedial graft for both fixation protocols did not exceed those of the intact anteromedial bundle. But at 30 degrees and 45 degrees of knee flexion, the in situ forces for fixation protocol 15/15 were 20.7% and 22.1% lower, respectively, when compared with the intact anteromedial bundle. Under combined rotatory loads, the anteromedial graft for fixation protocol 15/15 had in situ forces that were 45% lower than the intact anteromedial bundle at 30 degrees of knee flexion. The in situ force in the posterolateral graft for both fixation protocols did not exceed those of the intact posterolateral bundle, nor were they significantly different from the intact posterolateral bundle at any of the flexion angles tested.

CONCLUSION

Both fixation protocols restored knee kinematics without predisposing either graft to failure. Therefore, knee flexion angles between 15 degrees and 45 degrees for graft fixation were found to be safe for the anteromedial graft, while 15 degrees of knee flexion was safe for the posterolateral graft.

CLINICAL RELEVANCE

A range of knee flexion angles that is safe for the fixation of both grafts in double-bundle anterior cruciate ligament reconstruction was determined.

Effect of ACL deficiency on MCL strains and joint kinematics

The knee joint is partially stabilized by the interaction of multiple ligament structures. This study tested the interdependent functions of the anterior cruciate ligament (ACL) and the medial collateral ligament (MCL) by evaluating the effects of ACL deficiency on local MCL strain while simultaneously measuring joint kinematics under specific loading scenarios. A structural testing machine applied anterior translation and valgus rotation (limits 100 N and 10 N m, respectively) to the tibia of ten human cadaveric knees with the ACL intact or severed. A three-dimensional motion analysis system measured joint kinematics and MCL tissue strain in 18 regions of the superficial MCL. ACL deficiency significantly increased MCL strains by 1.8% (p<0.05) during anterior translation, bringing ligament fibers to strain levels characteristic of microtrauma. In contrast, ACL transection had no effect on MCL strains during valgus rotation (increase of only 0.1%). Therefore, isolated valgus rotation in the ACL-deficient knee was nondetrimental to the MCL. The ACL was also found to promote internal tibial rotation during anterior translation, which in turn decreased strains near the femoral insertion of the MCL. These data advance the basic structure-function understanding of the MCL, and may benefit the treatment of ACL injuries by improving the knowledge of ACL function and clarifying motions that are potentially harmful to secondary stabilizers.

The effect of anterior cruciate ligament deficiency on the in vivo elongation of the medial and lateral collateral ligaments

BACKGROUND

Although anterior cruciate ligament deficiency has been shown to lead to joint degeneration, few quantitative data have been reported on its effect on soft tissue structures surrounding the knee joint.

HYPOTHESIS

Anterior cruciate ligament deficiency will alter the deformation of both collateral ligaments during in vivo weight-bearing knee function from 0 degrees to 90 degrees.

STUDY DESIGN

Controlled laboratory study.

METHODS

Six patients who had acute anterior cruciate ligament injury in 1 knee with the contralateral side intact participated in this study. Using magnetic resonance and dual orthogonal fluoroscopic imaging techniques, we measured the length of the fiber bundles of the superficial medial collateral ligament, deep medial collateral ligament, and lateral collateral ligament of the 6 patients; the healthy contralateral knee of each patient served as a control.

RESULTS

Anterior cruciate ligament injury caused a significant elongation of the fiber bundles of the superficial and deep medial collateral ligament at every flexion angle. In contrast, the lateral collateral ligament fiber bundles shortened after anterior cruciate ligament injury.

CONCLUSION

The altered deformations of the collateral ligaments associated with the changes in tibiofemoral joint kinematics after anterior cruciate ligament injury demonstrate that deficiency of 1 of the knee joint structures upsets the in vivo knee homeostasis.

CLINICAL RELEVANCE

Restoring normal knee kinematics after anterior cruciate ligament reconstruction is critical to restore the normal function of the collateral ligaments.

Using navigation to measure rotation kinematics during ACL reconstruction

Rotational kinematics of the knee is not fully restored after single-bundle anterior cruciate ligament (ACL) reconstruction. Cadaveric experiments using knee testing machines have suggested anatomical reconstruction replacing the anteromedial and posterolateral bundles could restore knee kinematics more effectively than single-bundle reconstruction. However, practical tools to objectively assess knee rotational laxities clinically have not been available. We used an optically based computer-assisted navigation system to measure the tibiofemoral motion kinematics in four fresh whole cadavers. Standard clinical knee laxity tests (anterior drawer, Lachman, and pivot shift) were performed and the kinematics described in terms of tibial axial rotation and anteroposterior translation. Data were obtained for intact knees after excision of the ACL and sequential reconstruction of the anteromedial and posterolateral bundles. In the ACL-deficient knee, the mean maximum tibial rotation during the pivot shift test was 27 degrees and mean maximum translation 11 mm. Reconstruction of the anteromedial bundle reduced the rotational component to 18 degrees and translation to 7 mm. Reconstruction of the posterolateral bundle reduced rotation to 14 degrees . This pilot study suggests computer assisted navigation could provide a practical method to objectively measure the pivot shift and may be used clinically to demonstrate differences in the control of tibiofemoral rotation kinematics afforded by single and two-bundle ACL reconstructions.

Effects of local administration of vascular endothelial growth factor on mechanical characteristics of the semitendinosus tendon graft after anterior cruciate ligament reconstruction in sheep

BACKGROUND

Vascular endothelial growth factor (VEGF) is a potent mediator of angiogenesis.

HYPOTHESIS

An application of VEGF may enhance angiogenesis in the grafted tendon in anterior cruciate ligament (ACL) reconstruction, and the application may affect mechanical characteristics of the ACL graft.

STUDY DESIGN

Controlled laboratory study.

METHODS

Eighteen sheep were divided into groups I and II. In group I, the harvested semitendinosus tendon was soaked in VEGF solution, and the right knee then underwent ACL reconstruction using this tendon. In group II, the right knee underwent identical procedures to those of group I except that the harvested tendon was soaked in phosphate-buffered saline. All animals were sacrificed 12 weeks after ACL reconstruction.

RESULTS

Histologic findings showed that newly formed vessels and infiltrative fibroblasts were more abundant in group I than in group II. The anterior-posterior translation of the knee during an anterior-posterior force of +/- 100 N was significantly larger in group I than in group II by 2.58 mm (95% confidence interval, -1.76 mm to 1.76 mm) (P = .002). The linear stiffness of the femur-graft-tibia complex in group I was significantly lower than that in group II by 41.5 N/mm (95% confidence interval, -32.2 N/mm to 32.2 N/mm) (P = .017).

CONCLUSION

This study has revealed that VEGF as administered in this study promotes angiogenesis in the ACL graft and significantly reduces the stiffness of the ACL graft with increased knee laxity at 12 weeks after ACL reconstruction.

CLINICAL RELEVANCE

Exogenous VEGF application for ACL reconstruction can induce an increase in knee laxity and a decrease in the stiffness of the grafted tendon at least temporarily after ACL reconstruction. These potentially negative mechanical effects need to be taken into account when considering clinical use of VEGF.

The role of the medial collateral ligament and posteromedial capsule in controlling knee laxity

BACKGROUND

The medial aspect of the knee has a complex capsular structure; the biomechanical roles of specific structures are not well understood.

HYPOTHESIS

The 3 strong stabilizing structures, the superficial and deep medial collateral ligaments and the posteromedial capsule, make distinct contributions to controlling tibiofemoral laxity.

STUDY DESIGN

Controlled laboratory study.

METHODS

Changes in knee laxity under anterior-posterior drawer, valgus, and internal-external rotation loads were found by sequential cutting in 18 cadaveric knees. Three cutting sequences allowed the roles of the 3 structures to be seen in isolation and in combination. Some force contributions were also calculated.

RESULTS

The posteromedial capsule controlled valgus, internal rotation, and posterior drawer in extension, resisting 42% of a 150-N drawer force when the tibia was in internal rotation. The superficial collateral ligament controlled valgus at all angles and was dominant from 30 degrees to 90 degrees of flexion, plus internal rotation in flexion. The deep collateral ligament controlled tibial anterior drawer of the flexed and externally rotated knee and was a secondary restraint to valgus.

CONCLUSION

Distinct roles in controlling tibiofemoral laxity have been found for these structures that vary according to knee flexion and tibial rotation.

CLINICAL RELEVANCE

The restraining functions demonstrated provide new information about knee stabilization, which may allow better evaluation of structural damage at the medial aspect of the knee.