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Background: The medial collateral ligament (MCL) is frequently involved in injuries around the knee but is uncommonly treated surgically. There are various techniques to reconstruct the medial side of the knee, which have varying outcomes. Purpose/hypothesis: The purpose of the present systematic review and meta-analysis is to describe the clinical results of surgical management of acute and chronic isolated grade III MCL injury using various functional scores, such as IKDC, Lysholm, and VAS, and to ascertain complication rates associated with these interventions. Methods: A systematic review was performed according to the preferred reporting items for systematic reviews and meta-analysis (PRISMA) guidelines, and two independent authors (L.F and A.M) conducted a comprehensive search across multiple databases (PubMed, Web of Science, and Scopus). They reviewed each article's title and abstract for studies available until April 2024. The search terms used were "((MCL) OR (Medial collateral ligament)) AND (injuries) AND (treatment)". The full texts of the studies were evaluated when eligibility could not be assessed from the title and abstract. Results: The pooled proportion (percentage) of complications from the three studies reporting data on surgery for the MCL acute stage was 15.3% with 95% CI [6.1% to 24.6%]. No complications were reported in studies reporting surgery in the chronic stage. Marked resolution of pain was observed with the mean VAS Score for pain at the final follow-up after surgery for MCL injury in the acute stage was 0.4 with 95% CI [-0.04 to 0.84]. The mean IKDC score at the final follow-up in the three studies reporting data on surgery for the MCL in the acute stage was 79.39 with 95% CI [67.96 to 90.82], and in the chronic stage, was 85 with 95% CI [83.02 to 86.98]. The mean Lysholm Score at the final follow-up after surgery for MCL injury in the chronic stage was 83.04 with 95% CI [75.24 to 94.84], and in the acute stage was 95 with 95% CI [91.76 to 98.24]. Conclusion: This systematic review found that functional outcomes regarding IKDC and LYSHOLM scores were comparable for surgeries performed in acute and chronic MCL tears. There was a marginally increased risk of complication in surgeries performed for acute MCL tears. Compared to the acute phase, a marked resolution of pain was observed at the final follow-up after surgery for MCL injury. Study Design: Systematic review; level of evidence, 4.. [ABSTRACT FROM AUTHOR]

Purpose: The objective of this study was to conduct a comprehensive assessment of MLKI outcome studies in order to ascertain the overall rates of return to sport following MLKI. Methods: A systematic review was conducted based on the PRISMA guidelines. Quality assessment of the systematic review was performed using the MINORS Score. The following search terms were browsed in the title, abstract, and keyword fields: "multiligament knee" or "MLKI" AND "return to sport" or "sports activity" or "athletes" or "sports" or "sportsman". The resulting measures extracted from the studies were the rate of RTS, level of RTS, complications, revision surgery, Tegner, International Knee Documentation Committee (IKDC) Lysholm and anterior cruciate ligament-return to sport after injury (ACL-RSI). Results: A total of 439 patients were included in the study, of whom 383 (87.2%) were male and 56 (22.8%) were female. The mean age at surgery was 28.06 ± 8.93 years. The mean time from injury to surgery was 97.68 ± 127.81 weeks, while the mean follow-up was 42.83 ± 39.22 months. Of 312 patients who completed the follow-up and reported to be sportsmen before surgery, 184 (58.97%) returned to the same or higher pre-injury level, 58 (18.58%) returned to a lower level, while 69 (22.11%) did not return to sports activity. The author analysed the Tegner score in three studies and noted a decrease compared to the pre-injury level (from 7.12 ± 0.8 pre-injury to 4.59 ± 0.57 at the final follow-up; p < 0.001). At the final follow-up, 4 studies analysed IKDC with a mean value of 75.14 ± 9.6, 3 reported a mean Lysholm of 51.81 ± 27.6, and two reported a mean ACL-RSI of 64.82 ± 0.149. Among the 439 patients, a total of 90 (20.5%) complications/re-operations were reported, while a total of 29 (6.6%) failures were recorded. Conclusions: Return to sport after MLKI occurs in approximately 75% of surgically treated patients, though return to high-level sport is about 60% of the patients. Furthermore, one in five patients report complications, while the failure rate is relatively low (< 7%). Level of Evidence: Systematic review of level 4. [ABSTRACT FROM AUTHOR]

Background: Injuries of the superficial medial collateral ligament (sMCL) and anteromedial structures of the knee result in excess valgus rotation and external tibial rotation (ER) as well as tibial translation. Purpose: To evaluate a flat reconstruction of the sMCL and anteromedial structures in restoring knee kinematics in the combined MCL- and anteromedial-deficient knee. Study Design: Controlled laboratory study. Methods: Eight cadaveric knee specimens were tested in a 6 degrees of freedom robotic test setup. Force-controlled clinical laxity tests were performed with 200 N of axial compression in 0°, 30°, 60°, and 90° of flexion: 8 N·m valgus torque, 5 N·m ER torque, 89 N anterior tibial translation (ATT) force, and an anteromedial drawer test consisting of 89 N ATT force under 5 N·m ER torque. After determining the native knee kinematics, we transected the sMCL, followed by the deep medial collateral ligament (dMCL). Subsequently, a flat reconstruction of the sMCL with anteromedial limb, mimicking the function of the anteromedial corner, was performed. Mixed linear models were used for statistical analysis (P <.05). Results: Cutting of the sMCL led to statistically significant increases in laxity regarding valgus rotation, ER, and anteromedial translation in all tested flexion angles (P <.05). ATT was significantly increased in all flexion angles but not at 60° after cutting of the sMCL. A combined instability of the sMCL and dMCL led to further increased knee laxity in all tested kinematics and flexion angles (P <.05). After reconstruction, the knee kinematics were not significantly different from those of the native state. Conclusion: Insufficiency of the sMCL and dMCL led to excess valgus rotation, ER, ATT, and anteromedial tibial translation. A combined flat reconstruction of the sMCL and the anteromedial aspect restored this excess laxity to values not significantly different from those of the native knee. Clinical Relevance: The presented reconstruction might lead to favorable results for patients with MCL and anteromedial injuries with an anteromedial rotatory knee instability. [ABSTRACT FROM AUTHOR]

Anterior cruciate ligament and meniscus tears are common among sports injuries. There are different techniques for addressing anterior cruciate ligament and meniscus tears, with distinct indications, advantages, and disadvantages. We present the case of a 23-year-old male who underwent right anterior cruciate ligament reconstruction and posterior horn medial meniscus repair using an all-inside technique via superficial medial collateral ligament (sMCL) pie-crusting. Clinical examination and radiological investigations a few months later identified calcifications on the medial side of the right knee. We diagnosed the patient with heterotopic ossification post-sMCL pie-crusting; no apparent causal factors were present. To our knowledge, there have been no documented instances of heterotopic ossification following sMCL pie-crusting. In conclusion, heterotopic ossification may occur after sMCL pie-crusting; further studies are needed on this subject. [ABSTRACT FROM AUTHOR]

Background: Anteromedial rotatory instability (AMRI) of the knee is a complex and severe condition caused by injury to the anterior cruciate ligament and/or the medial collateral ligament. Clinical studies dealing with AMRI are rare, and objective measurements are nonexistent. Purpose/Hypothesis: The objectives of this study were, first, to quantify anteromedial rotatory knee laxity in healthy individuals using a noninvasive image analysis software and, second, to assess intra- and interrater reliability and equivalence in measuring anteromedial knee translation (AMT). It was hypothesized that AMT could be reliably quantified using a noninvasive image analysis software. Study design: Cohort study; Level of evidence, 3. Methods: This prospective proof-of-concept study included healthy individuals aged 16 to 40 years with no history of knee injury or surgery. Three adhesive surface markers were placed on predefined landmarks on the medial side of the knee. Three independent investigators examined anteromedial rotatory knee laxity with an anterior drawer test in different tibial rotations (neutral tibial rotation, 15° of external tibial rotation, and 15° of internal tibial rotation). The entire examination of each knee was recorded, and AMT including the side-to-side difference (SSD) was assessed using a freely available and validated image analysis software (PIVOT iPad application). Group comparisons were performed using a 1-way analysis of variance with Bonferroni-adjusted post hoc analysis. Intraclass correlation coefficients (ICCs) were calculated to assess inter- and intrarater reliability of AMT measurements. Equivalence of measurements was evaluated using the 2 one-sided t -test procedure. Results: Anteromedial rotatory knee laxity was assessed in 30 knees of 15 participants (53% male) with a mean age of 26.2 ± 3.5 years. In all 3 raters, the highest AMT was observed in neutral tibial rotation (range of means, 2.2-3.0 mm), followed by external tibial rotation (range of means, 2.0-2.4 mm) and internal tibial rotation (range of means, 1.8-2.2 mm; P <.05). Intrarater reliability of AMT (ICC, 0.88-0.96) and SSD (ICC, 0.61-0.96) measurements was good to excellent and moderate to excellent, respectively. However, interrater reliability was poor to moderate for AMT (ICC, 0.44-0.73) and SSD (ICC, 0.12-0.69) measurements. Statistically significant equivalence of AMT and SSD measurements was observed between and within raters for almost all testing conditions. Conclusion: Anteromedial rotatory knee laxity could be quantified using a noninvasive image analysis software, with the highest AMT observed during neutral tibial rotation in uninjured individuals. Reliability and equivalence of measurements were good to excellent within raters and moderate between raters. [ABSTRACT FROM AUTHOR]

Background: Combined injury of the anterior cruciate ligament (ACL) and the medial collateral ligament (MCL) is a common injury pattern and accounts for 20% of all ligamentous knee injuries. Despite advancements in surgical technique, there is no up-to-date consensus regarding the superiority of nonoperative versus operative management in higher-grade MCL tears of combined ACL-MCL injuries. Purpose: To interpret recent literature on treatment options and to provide an updated evidence-based approach for management of combined ACL-MCL knee injuries. Study Design: Systematic review and meta-analysis; Level of evidence, 4. Methods: We performed a systematic review on outcomes following treatment of concomitant ACL and MCL injuries. A computerized search was conducted in PubMed, Embase.com, and Scopus.com. Authors independently assessed eligible studies and screened titles and abstracts. Articles reporting on patients with concomitant ACL and MCL injuries with or without concomitant procedures were included. Data regarding study design, sample size, patient age and sex, length of follow-up, timing of surgery, indications, surgical methods, concomitant procedures, outcomes, and complications were recorded. Patient-reported outcomes (PROs) and functional outcomes, including Knee injury and Osteoarthritis Outcome Score, International Knee Documentation Committee scores, Lysholm and Tegner scores, and range of motion, were estimated via meta-analysis and compared statistically by surgical approach. Results: In total, 18 studies were included in the systematic review with level 1 to level 4 evidence, with a total of 1,534 cases, were included in the systematic review. Of these, 16 studies with sufficient statistical reporting including 997 cases with sufficient follow-up were included in meta-analysis. Three different approaches to combined ACL-MCL injuries were identified: ACL reconstruction with (1) nonoperative MCL, (2) MCL repair, and (3) MCL reconstruction. There was no statistical difference between nonoperative versus surgically managed MCL injuries for PROs, range of motion at final follow up, or quadriceps strength. Conclusion: Reconstruction of combined injury in a delayed fashion facilitates return of range of motion and may allow time for low-grade MCL tears to heal. If residual valgus or anteromedial rotatory laxity remains after a period of rehabilitation, then concomitant surgical management of ACL and MCL injuries is warranted. Avulsion MCL injuries and Stener-type lesions may benefit from early repair techniques. [ABSTRACT FROM AUTHOR]

BACKGROUND: Return to the preinjury level of play after a 2-or-more-ligament knee injury is a challenge, with research suggesting that injury pattern and rehabilitation quality are key variables to consider. CASE PRESENTATION: A 22-year-old male basketball player suffered a 2-ligament knee injury involving the anterior cruciate ligament, medial collateral ligament, and both menisci. He underwent reconstructive surgery and completed his rehabilitation and return-to-sport training within 1 facility. OUTCOME AND FOLLOW-UP: After 12 months of extensive rehabilitation, objective testing confirmed the recovery of the athlete's surgical limb performance. He returned to his preinjury level of play and signed a professional contract to play elite-level basketball in Europe. DISCUSSION: The athlete required more than a year of extensive rehabilitation to return to elite-level basketball. After a 2-or-more-ligament knee injury, comprehensive rehabilitation programs are required to support an athlete's return to their preinjury level of play. [ABSTRACT FROM AUTHOR]

Background: Both the superficial medial collateral ligament (sMCL) and the deep MCL (dMCL) contribute to the restraint of anteromedial (AM) rotatory instability (AMRI). Previous studies have not investigated how MCL reconstructions control AMRI. Purpose/Hypothesis: The purpose was to establish the optimal medial reconstruction for restoring normal knee kinematics in an sMCL- and dMCL-deficient knee. It was hypothesized that AMRI would be better controlled with the addition of an anatomically shaped (flat) sMCL reconstruction and with the addition of an AM reconstruction replicating the function of the dMCL. Study Design: Controlled laboratory study. Methods: A 6 degrees of freedom robotic system equipped with a force-torque sensor was used to test 8 unpaired knees in the intact, sMCL/dMCL sectioned, and reconstructed states. Four different reconstructions were assessed. The sMCL was reconstructed with either a single-bundle (SB) or a flattened hamstring graft aimed at better replicating the appearance of the native ligament. These reconstructions were tested with and without an additional AM reconstruction. Simulated laxity tests were performed at 0°, 30°, 60°, and 90° of flexion: 10 N·m valgus rotation, 5 N·m internal and external rotation (ER), and an AM drawer test (combined 134-N anterior tibial drawer in 5 N·m ER). The primary outcome measures of this force-controlled setup were anterior tibial translation (ATT; in mm) and axial tibial rotation (in degrees). Results: Sectioning the sMCL/dMCL increased valgus rotation, ER, and ATT with the simulated AM draw test at all flexion angles. SB sMCL reconstruction was unable to restore ATT, valgus rotation, and ER at 30°, 60°, and 90° of flexion to the intact state (P <.05). Flat MCL reconstruction restored valgus rotation at all flexion angles to the intact state (P >.05). ER was restored at all angles except at 90°, but ATT laxity in response to the AM drawer persisted. Addition of an AM reconstruction improved control of ATT relative to the intact state at all flexion angles (P >.05). Combined flat MCL and AM reconstruction restored knee kinematics closest to the intact state. Conclusion: In a cadaveric model, AMRI resulting from an injured sMCL and dMCL complex could not be restored by an isolated SB sMCL reconstruction. A flat MCL reconstruction or an additional AM procedure, however, better restored medial knee stability. Clinical Relevance: In patients evaluated with a combined valgus and AM rotatory instability, a flat sMCL and an additional AM reconstruction may be superior to an isolated SB sMCL reconstruction. [ABSTRACT FROM AUTHOR]

Injuries to the intra-articular anterior cruciate ligament (ACL) and the extraarticular medial collateral ligament (MCL) result in significant knee joint instability, pain, and immobility. Moderate endurance-type exercise can increase ligament strength but little is known on the effect of short-term regular bouts of high-intensity exercise on the extracellular matrix (ECM) structure of knee ligaments. Therefore, this study aimed to identify the effect of short-term regular bouts high exercise on the proteome of the rat ACL and MCL using mass spectrometry. Sprague-Dawley male rats (n = 6) were split into control and exercise groups, and subjected to high-intensity training for four 4 weeks followed by proteomic analyses of the ACL and MCL. Knee joint health status was assessed using OARSI and a validated histological scoring system. Histopathological analyses demonstrated no significant changes in either in cruciate, collateral ligaments, or cartilage between the control and exercised knee joints. However, significant proteins were found to be more abundant in the exercised ACL compared to ACL control group but not between the exercised MCL and control MCL groups. The significant abundant proteins in ACL exercise groups were mostly cytoskeletal, ribosomal and enzymes with several abundant matrisomal proteins such as collagen proteins and proteoglycans being found in this group. In conclusion, our results indicate that short-term regular bouts of high-intensity exercise have an impact on the intra-articular ACL but not extra-articular MCL ECM protein expression. [ABSTRACT FROM AUTHOR]

Purpose: Medial collateral ligament (MCL) injury is very common and surgical repair is sometimes necessary. Especially in the setting of simultaneous anterior cruciate ligament reconstruction (ACLR) as the ACL is the secondary restraint against valgus stress. The goal of this study was to evaluate knee biomechanics after suture repair of the MCL augmented with suture tape, as compared to MCL repair alone, in the setting of concomitant ACL reconstruction (ACLR). Methods: Fifteen fresh-frozen human cadaveric knees were tested using a six-degrees-of-freedom robotic system under four loadings: (a) an 89.0 N anterior tibial load, (b) a 5.0 Nm internal and external rotation torque, (c) a 10.0 Nm valgus load, (d) a 7.0 Nm valgus load combined with 5.0 Nm internal rotation torque as a static simulated pivot-shift. The tested conditions were ACLR with the following states: (1) MCL intact, (2) MCL deficient, (3) MCL Repair, and (4) MCL repair augmented with suture tape (MCL Repair + ST). Under the different knee loadings, the tibial displacement, and the force in either the intact MCL, suture repaired MCL or repaired MCL-suture tape complex was measured. Results: While neither the MCL Repair nor the MCL Repair + ST restored valgus rotation to the MCL intact state, displacement was significantly smaller after MCL Repair + ST (p < 0.05). The knee rotation under external rotation torque in MCL Repair + ST did not differ MCL intact (n.s.), while with MCL Repair the rotation was significantly greater (p < 0.05). MCL Repair + ST did not cause an over-constraint of the knee in any of the tested loading conditions. Conclusion: In a combined ACL-reconstruction-MCL-repair model, MCL Repair augmented with suture tape improved valgus and external rotation laxity when compared to MCL suture repair alone. Suture tape augmentation may provide this additional means of stabilization and can be added at the time of surgical repair of the MCL. Clinically this may result in lower failure rates and less residual laxity after MCL repair, as well as shorter immobilization times and faster return to play. [ABSTRACT FROM AUTHOR]

Purpose: Ultrasound (US) examination of the medial joint space of the knee has played a subordinate diagnostic role up till now. The purpose of the present study was to describe mean values of medial joint width and to investigate the impact of gender, age, and body mass index (BMI) on medial joint laxity in healthy knees using modern, dynamic US in a standardized fashion in unloaded and standardized loaded conditions. Methods: A total of 65 subjects with 79 healthy knees were enrolled in this study. All volunteers underwent clinical examination of the knee. The medial knee joint width was determined using US in a supine position at 0° and 30° of knee flexion in unloaded and standardized loaded (= 15 Dekanewton, daN) conditions using a specific device. Mean values were described and correlations between medial knee joint width and gender, age, and BMI were assessed. Results: Thirty-two females and 33 males were enrolled in this study. The mean medial joint width in 0° unloaded was 5.7 ± 1.2 mm and 7.4 ± 1.4 mm loaded. In 30° of knee flexion, the mean medial joint width was 6.1 ± 1.1 mm unloaded and 7.8 ± 1.2 mm loaded. The average change between unloaded and loaded conditions in 0° was 1.7 ± 1.0 mm and in 30° 1.7 ± 0.9 mm. A significant difference between genders was evident for medial joint width in 0° and 30° of flexion in unloaded and loaded conditions (p < 0.05). With rising age, a significant increased change of medial joint space width between unloaded and loaded conditions could be demonstrated in 0° (p = 0.032). No significant correlation between BMI and medial joint width in US could be found. Conclusion: Mean values of medial joint width in unloaded and standardized loaded conditions using a fixation device could be demonstrated. Based on the results of this study, medial knee joint width in US is gender- and age-related in healthy knees. These present data may be useful for evaluating patients with acute or chronic pathologies to the medial side of the knee. Level of evidence: III. [ABSTRACT FROM AUTHOR]

Background: To investigate the effect of complete rupture of the posterior cruciate ligament (PCL) on the biomechanics and histology of the medial collateral ligament (MCL). Materials and methods: Seventy-two male rabbits were randomly divided into two groups: the ruptured group was treated with complete PCL amputation, while the intact group was only subjected to PCL exposure without amputation. Eighteen rabbits were randomly sacrificed at 8, 16, 24, and 40 weeks after the operation, and their specimens were processed for mechanical tensile testing, nano-indentation experiments, hematoxylin-eosin (HE) staining, and picrosirius-polarization staining. Results: There was no significant difference in the length and maximum displacement of the MCL between the ruptured group and the intact group at each time point. The maximum load of the ruptured group was significantly smaller than that of the intact group at 40 W. The elastic modulus and micro-hardness of the ruptured group increased significantly at 24 W and decreased significantly at 40 W. At 16 W and 24 W after PCL rupture, the number of type I collagen fibers and type III collagen fibers in the MCL of the ruptured group was significantly increased compared with that of the intact group. While the type I collagen fibers of the ruptured group were significantly decreased compared with the intact group at 40 W, there was no significant difference in type III collagen fibers between the ruptured group and the intact group. Conclusion: PCL rupture has no significant effect on the mechanical and histological properties of MCL in a short period of time under physiological loading, but the histological and mechanical properties of MCL decrease with time. [ABSTRACT FROM AUTHOR]

Background: Lesions of the medial collateral ligament (MCL) are the most common knee ligament injuries and, when they occur in isolation, they often progress with satisfactory outcomes using conservative treatment. However, MCL lesions associated with anterior cruciate ligament or posterior cruciate ligament (PCL) injuries in knee dislocations should be reconstructed to prevent failure of the central pivot. In knees with combined injuries involving the PCL and the MCL, the confluence of tunnels in the medial femoral condyle can be a potential problem during reconstruction surgery. Indications: The indication of this technique is the combined injury of the PCL and the MCL. Technique Description: The technique consists in the reconstruction of the PCL and the MCL with an Achilles tendon allograft. The bone plug of the graft is fixed on the tibial bed with the inlay technique. The graft passes through a single femoral tunnel drilled in the medial femoral condyle, with entrance point on the footprint of the PCL on the inner wall of the condyle and exit on the origin of the native MCL, near to the medial epicondyle. The graft is fixed in the femoral tunnel with an interference screw and continues to the isometric point of the anatomic insertion of the MCL in the tibia, where an interference screw is used to fix it. Results: Results from our group using this technique have shown good clinical outcomes, with complications and failure rates similar to other series in the literature. Discussion/Conclusion: This technique is an excellent option for surgeons, when an Achilles tendon allograft is available, to avoid confluence of tunnels in the medial femoral condyle. It presents good results and acceptable complication rates, compatible with the severity of this lesion. Patient Consent Disclosure Statement: The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication. Graphical Abstract This is a visual representation of the abstract. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of the present study was to determine how the medial structures and ACL contribute to restraining anteromedial instability of the knee.Methods: Twenty-eight paired, fresh-frozen human cadaveric knees were tested in a six-degree of freedom robotic setup. After sequentially cutting the dMCL, sMCL, POL and ACL in four different cutting orders, the following simulated clinical laxity tests were applied at 0°, 30°, 60° and 90° of knee flexion: 4 Nm external tibial rotation (ER), 4 Nm internal tibial rotation (IR), 8 Nm valgus rotation (VR) and anteromedial rotation (AMR)-combined 89 N anterior tibial translation and 4 Nm ER. Knee kinematics were recorded in the intact state and after each cut using an optical tracking system. Differences in medial compartment translation (AMT) and tibial rotation (AMR, ER, IR, VR) from the intact state were then analyzed.Results: The sMCL was the most important restraint to AMR, ER and VR at all flexion angles. Release of the proximal tibial attachment of the sMCL caused no significant increase in laxity if the distal sMCL attachment remained intact. The dMCL was a minor restraint to AMT and ER. The POL controlled IR and was a minor restraint to AMT and ER near extension. The ACL contributed with the sMCL in restraining AMT and was a secondary restraint to ER and VR in the MCL deficient knee.Conclusion: The sMCL appears to be the most important restraint to anteromedial instability; the dMCL and POL play more minor roles. Based on the present data a new classification of anteromedial instability is proposed, which may support clinical examination and treatment decision. In higher grades of anteromedial instability an injury to the sMCL should be suspected and addressed if treated surgically. [ABSTRACT FROM AUTHOR]

The multiple ligament knee injury involving the medial collateral ligament, anterior cruciate ligament, and posterior cruciate ligament is typically the result of a high-energy trauma or knee dislocation event. Optimal treatment strategies are debated, specifically in regard to timing of surgery, reconstruction/repair techniques, and postoperative protocols. This review details the stepwise treatment of these complex patients from diagnosis to postoperative rehabilitation and summarizes the current literature. [ABSTRACT FROM AUTHOR]

Knee pain is among the most common problems in active patients, with common causes of medial knee pain including meniscal injury, osteoarthritis, medial collateral ligament (MCL) injury, and pes anserine bursopathy/distal hamstring tendinopathy. Some cases of medial knee pain are refractory to standard treatment options and may be caused by rare pathology. We present a case of medial knee pain secondary to medial tibial crest friction syndrome (MTCFS) in a 22-year-old male training for a sprint triathlon after rapidly increasing his training program. Magnetic resonance imaging revealed bone marrow and soft-tissue edema about the MTC deep to the MCL consistent with MTCFS. The patient failed a period of relative rest and activity modification, but improved with corticosteroid injection deep to the MCL in the location of his symptoms. This case highlights a potential management option for MTCFS, a disorder previously described only in radiologic literature. [ABSTRACT FROM AUTHOR]

Purpose: Medial collateral ligament (MCL) injury is the single most common traumatic knee injury in football. The purpose of this study was to study the epidemiology and mechanisms of MCL injury in men's professional football and to evaluate the diagnostic and treatment methods used.Methods: Fifty-one teams were followed prospectively between one and three full seasons (2013/2014-2015/2016). Individual player exposure and time-loss injuries were recorded by the teams' medical staffs. Moreover, details on clinical grading, imaging findings and specific treatments were recorded for all injuries with MCL injury of the knee as the main diagnosis. Agreement between magnetic resonance imaging (MRI) and clinical grading (grades I-III) was described by weighted kappa.Results: One hundred and thirty of 4364 registered injuries (3%) were MCL injuries. Most MCL injuries (98 injuries, 75%) occurred with a contact mechanism, where the two most common playing situations were being tackled (38 injuries, 29%) and tackling (15 injuries, 12%). MRI was used in 88 (68%) of the injuries, while 33 (25%) were diagnosed by clinical examination alone. In the 88 cases in which both MRI and clinical examination were used to evaluate the grading of MCL injury, 80 (92% agreement) were equally evaluated with a weighted kappa of 0.87 (95% CI 0.77-0.96). Using a stabilising knee brace in players who sustained a grade II MCL injury was associated with a longer lay-off period compared with players who did not use a brace (41.5 (SD 13.2) vs. 31.5 (SD 20.3) days, p = 0.010).Conclusion: Three-quarter of the MCL injuries occurred with a contact mechanism. The clinical grading of MCL injuries showed almost perfect agreement with MRI grading, in cases where the MCL injury is the primary diagnosis. Not all grade II MCL injuries were treated with a brace and may thus indicate that routine bracing should not be necessary in milder cases.Level Of Evidence: Prospective cohort study, II. [ABSTRACT FROM AUTHOR]

Background: In cases of acute combined posteromedial and anterior cruciate ligament (ACL) injuries, primary repair of the superficial medial collateral ligament (sMCL) and posterior oblique ligament (POL) with suture tape augmentation may be a reasonable alternative to standard tendon reconstruction techniques. Purpose/Hypothesis: The purpose was to examine the rotational and valgus laxity with ACL strain following sMCL and POL repair with suture tape augmentation at various degrees of knee flexion. It was hypothesized that this technique would restore knee laxity and kinematics comparable with those of the intact state. Study Design: Controlled laboratory study. Methods: Ten cadaveric knee specimens (mean ± SD, 57.9 ± 5.9 years) were obtained. Specimens were tested with the tibia fixed and the femur mobile on an X-Y table. Each specimen was tested in 4 conditions according to the state of the sMCL and POL: native, deficient, repaired with suture tape augmentation, and reconstructed with tendon allografts. Valgus laxity was tested with 40-N force applied in the lateral direction of the femur, and rotational motion was tested with 5-N torque applied to the tibia. ACL strain during valgus stress was also measured. Each condition was tested in 0°, 15°, 30°, 45°, and 60° of knee flexion. Results: Dissection of the sMCL and POL led to significantly increased valgus laxity in all flexion angles, with a significant increase in ACL strain at 30° (P <.001) and 45° (P <.001). Ligament repair with suture tape augmentation demonstrated similar valgus and rotational laxity as compared with intact specimens, with the exception of increased internal rotation at 30° (P =.005). Ligament reconstruction resulted in significantly increased valgus opening at 45° (P =.048) and significantly increased internal rotation at 30° (P <.001) as compared with the native state. Direct comparison between surgical techniques showed no significant differences. Conclusion: At time zero, ligament repair of the posteromedial knee with suture tape augmentation restored close-to-native valgus and rotatory laxity, as well as native ACL strain for cases of complete sMCL and POL avulsion. Clinical Relevance: Ligament repair of the sMCL and POL with suture tape augmentation may be a reasonable alternative to tendon reconstruction techniques in cases of acute combined posteromedial and ACL injuries with valgus and rotatory instability. [ABSTRACT FROM AUTHOR]

Purpose: Medial soft tissue release in a varus deformity knee during total knee arthroplasty is essential for accurate balancing of the reconstruction. This study attempts to quantify the effect of sequential needle puncturing of the medial collateral ligament (MCL) using a pressure sensor insert (Verasense by OrthoSensor) and gap measurement under tension.Methods: Cruciate-retaining arthroplasties were placed in 14 cadaveric knees. The MCL was elongated by step-wise perforation, in five sets of five perforations, with the use of an 18-gauge needle, followed by valgus stress. Following the fifth set of needle perforations, blade perforation was performed on the remaining tense fibers of the MCL. Following each step-wise perforation, corresponding medial compartment pressures and gap measurements under tension were recorded.Results: Sensor measurements correlated closely with step-wise tissue release (R = 0.73, p < 0.0001), and a significant decrease in pressure was found in early needle puncturing (mean 49 N after 5, 83 N after 15, p values < 0.05), although changes diminished at later stages of needle perforation (90 N after 20). Gap measurement demonstrated small gradual changes with early puncturing, but showed significant opening in the later stages of release. There was minimal variation in pressure or gap measurements in flexion versus extension. This finding suggests that MCL needle puncture will not lead to unequal gaps between flexion and extension. There were no cases of MCL over-release after 15 punctures, one case after 20 punctures, and three after blade perforation.Conclusion: Needle puncturing of the MCL in extension for up to 15 punctures can be a safe and predictable way to achieve medial opening when balancing a varus knee during TKA as demonstrated in this cadaveric model. Blade perforation should be used with caution to avoid over-release. The needle puncture method can be used by surgeons to achieve reliable reductions in medial compartment pressures, to help achieve a balanced TKA, with minimal risk of over-release. [ABSTRACT FROM AUTHOR]

Background: A hamstring autograft is commonly used in anterior cruciate ligament (ACL) reconstruction (ACLR); however, there is evidence to suggest that the tendons harvested may contribute to medial knee instability. Hypothesis: We tested the hypothesis that the gracilis (G) and semitendinosus (ST) tendons significantly contribute to sagittal, coronal, and/or rotational knee stability in the setting of ACLR with a concurrent partial medial collateral ligament (MCL) injury. Study Design: Controlled laboratory study. Methods: Twelve human cadaveric knees were subject to static forces applied to the tibia including an anterior-directed force as well as varus, valgus, and internal and external rotation moments to quantify laxity at 0°, 30°, 60°, and 90° of flexion. The following ligament conditions were tested on each specimen: (1) ACL intact/MCL intact, (2) ACL deficient/MCL intact, (3) ACL deficient/partial MCL injury, and (4) ACLR/partial MCL injury. To quantify the effect of muscle loads, the quadriceps, semimembranosus, biceps femoris, sartorius (SR), ST, and G muscles were subjected to static loads. The loads on the G, ST, and SR could be added or removed during various test conditions. For each ligament condition, the responses to loading and unloading the G/ST and SR were determined. Three-dimensional positional data of the tibia relative to the femur were recorded to determine tibiofemoral rotations and translations. Results: ACLR restored anterior stability regardless of whether static muscle loads were applied. There was no significant increase in valgus motion after ACL transection. However, when a partial MCL tear was added to the ACL injury, there was a 30% increase in valgus rotation (P < .05). ACLR restored valgus stability toward that of the intact state when the G/ST muscles were loaded. A load on the SR muscle without a load on the G/ST muscles restored 19% of valgus rotation; however, it was still significantly less stable than the intact state. Conclusion: After ACLR in knees with a concurrent partial MCL injury, the absence of loading on the G/ST did not significantly alter anterior stability. Simulated G/ST harvest did lead to increased valgus motion. These results may have important clinical implications and warrant further investigation to better outline the role of the medial hamstrings, particularly among patients with a concomitant ACL and MCL injury. Clinical Relevance: A concurrent ACL and MCL injury is a commonly encountered clinical problem. Knowledge regarding the implications of hamstring autograft harvest techniques on joint kinematics may help guide management decisions. [ABSTRACT FROM AUTHOR]

The medial collateral ligament (MCL) is a major stabilizer of the knee joint. It is the most common ligament injured in the knee, particularly in athletes, and has been reported to be torn in 7.9% of all knee injuries.2 The MCL has a complex, layered anatomy with multiple insertions and functions. Minor trauma can cause tearing of the superficial portion whereas higher energy mechanisms can disrupt both the deep and superficial layers. History and physical are often adequate, but the gold standard for diagnosis is MRI. Lesser injuries to the MCL can often be treated conservatively with early rehabilitation, but more significant tears often necessitate surgery. A thorough understanding of the MCL and associated injuries is essential for proper diagnosis and treatment. [ABSTRACT FROM AUTHOR]

Intra-articular entrapment of the medial collateral ligament (MCL) is a rare but recognised complication of traumatic injury to the posteromedial corner (PMC) of the knee. Considering the MCL is the most commonly injured ligament of the knee this complication is extremely rare with only a handful of cases describing MCL entrapment following distal avulsion of the MCL. We present the first known case of MCL entrapment following proximal avulsion of the MCL and posterior oblique ligament (POL) with the mid-substance of the MCL becoming entrapped in the joint, lying on the superior surface of the medial meniscus and extending up into the intercondylar notch. In addition, the medial patellar retinaculum was also entrapped in the medial aspect of the medial patellofemoral joint. MCL entrapment is best treated with expeditious surgical intervention and it is therefore crucial that the MRI findings are not overlooked. Details of the clinical assessment, MRI and operative findings are presented with a literature review of MCL entrapment. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Background: There is an on-going discussion whether to operatively treat combined grade II and III lesions of the medial collateral ligament (MCL) with anterior cruciate ligament (ACL) in the acute phase rather than conservative treatment of the MCL lesion with a delayed unitary ACL replacement. Another issue is the question how to technically address these MCL lesions. The aim of this study was, therefore, to analyze the results of simultaneous ACL replacement (hamstrings) in a single-bundle technique with a simultaneous MCL ligament bracing procedure.Methods: In this prospective non-randomized trial,, 16 patients were included with grade II and III lesions of the MCL. Surgical treatment was performed within 14 days (mean 10.4 days, SD ±2.3 days) by one single expert orthopedic surgeon using the semitendinosus tendon and Rigidfix® system for femoral and tibial fixation and 3.5 mm screws with one 1.3 mm PDS Cord for minimal-invasive MCL ligament bracing with screw fixation. Knee stability was measured with the Rolimeter® and KT-1000®. MCL stability was assessed in clinically and radiographically with valgus stress projections.Results: The mean patient age was 36.4 with six female and ten male patients. There were no surgical complications such as infections or healing disturbances. Mean operation time was 64 ± 6 min. The arthrofibrosis rate was 0 %. Medial knee stability was normal in full extension for all cases with no intra-individual side-to-side difference. Radiological assessed MCL stability revealed Δ values with a mean of 1.1 ± 1.3 mm compared to the contra-lateral side. The Lachman Test revealed a side-to-side difference of 1.6 mm with the KT-1000® and 2.6 ± 0.9 mm when measured with the Rolimeter®. Subjective clinical assessment revealed good results with a mean Lysholm Score of 89.1 points.Conclusion: Acute ACL replacement and MCL ligament bracing with this novel technique revealed in this study good clinical results and objective restored knee stability without cases of knee stiffness or arthrofibrosis. The remarkable shortcoming is the small cohort number making further studies necessary. [ABSTRACT FROM AUTHOR]

The article investigates the relative anterior cruciate ligament (ACL) and medial collateral ligament (MCL) strain patterns during physiological simulation of high-risk dynamic landing conditions. A novel in sim approach is used to examine ACL and MCL strain following knee abduction and internal tibial rotation moments. It looks at the determinants of resultant ACL:MCL strain ratio levels. The importance of understanding injury mechanisms for injury prevention strategies is also emphasized.

The article presents a study that compares the kinematics of an anatomic superficial medial collateral ligament (sMCL) augmented repair and anatomic sMCL reconstruction to the native intact and sectioned sMCL states by use of a robotic system. The study reveals lack of significant differences between the anatomic augmented repair and anatomic reconstruction. Similarity in behavior between the 2 reconstruction groups failed to produce the intact state.

Background:Little has been written about the use of radiographic landmarks for locating the origin of the superficial medial collateral ligament (sMCL). A standardized radiographic landmark for the sMCL origin using intraoperative fluoroscopic imaging may be of value in aiding the surgeon in accurate femoral tunnel placement in the setting of extensive soft tissue disruption and bony attrition.Purpose:To determine a reproducible radiographic landmark that will assist in correct femoral tunnel placement in sMCL repair and reconstruction.Study Design:Descriptive laboratory study.Methods:Ten fresh-frozen unmatched human cadaveric knees were dissected, and the origin of the sMCL was exposed. A 2-mm metallic marker was then placed at the center of the femoral origin of the sMCL. True lateral fluoroscopically assisted digital radiographs were obtained of the knee with the posterior and distal femoral condyles overlapping in a standardized fashion. With the use of computer software, reference lines were drawn on the images, creating 4 quadrants. Two independent examiners performed quantitative measurements of the sMCL origin in relation to this axis and to the Blumensaat line.Results:Mean measurements showed the sMCL origin to be closely related to the intersection point of the Blumensaat line and a line drawn distally from the posterior femoral cortex on a true lateral radiograph. The sMCL origin was found at a mean point 1.6 ± 4.3 mm posterior and 4.9 ± 2.1 mm proximal to the intersection of a line paralleling the posterior femoral cortex and a line drawn perpendicular to the posterior femoral cortical line, where it intersects the Blumensaat line. In 5 of 10 specimens, the center of the sMCL origin fell precisely on the Blumensaat line. The remaining specimens had sMCL origins anterior to the Blumensaat line. The femoral origin of the sMCL was found in the proximal and posterior quadrants in 8 of 10 specimens.Conclusion:With a relatively small amount of deviation, the sMCL origin can be consistently identified on a true lateral radiograph of the knee using reproducible reference lines on fluoroscopic imaging.Clinical Relevance:Accurate identification of the femoral origin of the sMCL can be accomplished by intraoperative fluoroscopic imaging. This information may be of significant benefit in repairing acute injuries and in reconstructive procedures complicated by bony attrition and soft tissue loss. [ABSTRACT FROM AUTHOR]

Abstract: Lysyl oxidase (LOX) family has the capacity to catalyse the cross-linking of collagen and elastin, implicating its important fundamental roles in tissue development and injury healing. However, the variations in expression of the LOX family in the normal and injured anterior cruciate ligament (ACL) are not fully known. To better understand the role of LOX family in the self-healing inability mechanism of injured ACL, this study is to measure the LOX family's differential expressions in ACL and medial collateral ligament (MCL) fibroblasts after mechanical injury induced by using an equi-biaxial stretching chamber. The cells received various degrees of mechanical stretch 0% (resting state), 6% (physiological state) and 12% (injurious state), respectively. The gene profile and protein expressions were analysed by semi-quantitative PCR, quantitative real-time PCR and Western blotting. At physiological state, gene expression showed LOX in ACL was 2.6–5.2 folds higher than that in MCL in all culture time periods, LOXL-4 1.2–3.6 folds, but LOXL-3 in MCL showed 1.1–4.8 folds higher than that in ACL. In injurious state, MCL gene expressions were 2.8–29.6 folds higher than ACL in LOX, LOXL-2, LOXL-3 and LOXL-4 at 2, 6 and 12h periods. These differential expression profiles of the LOX family in the two ligament tissues were further used to explain the intrinsic differences between ACL and MCL, and why injured ACL could not be amenable to repair itself, whereas MCL could. [Copyright &y& Elsevier]

Context: Knee injuries, particularly of the medial collateral ligament (MCL), are the most common injury sustained in American football. In 1979, Anderson et al described a knee brace that could protect uninjured knees from MCL injuries resulting from lateral impact. Since then, a number of light and free-moving bracing devices have been developed. However, the efficacy of prophylactic knee bracing remains in question.Objective: A systematic review of the efficacy of prophylactic knee bracing in preventing MCL injuries in football players.Data Sources: Based on MedSearch and PubMed, articles from 1985 to November 2009 were identified with the following keywords and their combinations: prophylactic, prevent injury, knee brace, prevention, medial collateral ligament, MCL, football, and bracing.Study Selection: One randomized controlled trial (level 1 study) and 5 prospective cohort studies (level 2 studies) were selected.Results: The results of the studies were inconsistent; only 1 study showed that prophylactic knee bracing significantly reduced MCL injuries (P < .05). In contrast, 2 studies found that knee bracing was associated with an increase in knee injuries.Conclusions: Prophylactic bracing in American football has not consistently reduced MCL injuries. There remains a lack of evidence to support the routine use of prophylactic knee bracing in uninjured knees. There is limited high-level evidence, bias in the available literature, and confounding variables that limit the current literature. [ABSTRACT FROM AUTHOR]

The human ACL (anterior cruciate ligament) is susceptible to injury but has poor healing response, whereas an injured MCL (medial collateral ligament) can be repaired relatively well. Since MMPs (matrix metalloproteases) and TIMPs (tissue inhibitor of metalloproteases) are involved in this tissue remodeling process, investigation of different response of MMPs and TIMPs family in ACL and MCL fibroblasts might lead to understanding the differential matrix remodeling process as well as their different healing ability. The first step would be determination of whether these tissue remodeling effectors are present in ligaments. In this study, we designed primers for real-time RT-PCR and determined the expression of MMPs and TIMPs family in ACL and MCL fibroblasts with synovium as a positive control. Semiquantitative RT-PCR revealed that multiple MMPs and TIMPs expressed in human ACL and MCL fibroblasts except MMP-8, 10, 12, 13, 15, 16, 20, and 26. MMP-7 was present in MCL but not in ACL fibroblast. Quantitative real-time RT-PCR showed that mRNA levels of MMP-1, 2, 14, 17, 23A, and 23B and TIMP-4 are significantly higher in MCL than in ACL fibroblasts. However, MMP-3 is higher in ACL than in MCL fibroblasts. We conclude that numerous MMPs and TIMPs family members that are differentially expressed in ACL and MCL might be involved in the differential matrix remodeling process as well as the differential healing ability of ACL and MCL. [ABSTRACT FROM AUTHOR]

This article examines the use of an Achilles tendon allograft to reconstruct a chronically deficient medial collateral ligament (MCL). MCL reconstruction is for patients with symptomatic valgus instability and excessive medial compartment opening. Treatment of MCL tears is nonoperative. Contraindications to this technique include ongoing active infection and degenerative changes of the medial or the lateral compartment.

Although an injured medial collateral ligament (MCL) will naturally heal, the quality of healing tissue is inferior to the uninjured MCL tissue. Previous studies have shown promising results of sodium orthovanadate (vanadate) in enhancing the quality of rat skin wounds. This study therefore investigated whether vanadate enhances the quality of the rat healing MCL in terms of the collagen fibril organization and diameter. Six mature male Sprague-Dawley rats, with weight ranges of 475-505 g and ages of 25 weeks, were used in this study. Three rats in the experimental group received vanadate (0.2 mg/ml) in their saline drinking water (150 mM NaCl), whereas three rats in the control group were only given saline water. Three weeks after transection, the rat MCLs were harvested for hematoxylin and eosin (H&E) staining and transmission electron microscopy. It was found that vanadate promoted organization of collagen fibrils and significantly increased the diameters of collagen fibrils by 14% in healing MCL (P<0.001). These results indicate that application of vanadate may be a promising tissue engineering approach to enhance the quality of healing tissues such as injured MCLs. [ABSTRACT FROM AUTHOR]

To perform an open-wedge high-tibial osteotomy (HTO), the medial proximal tibia is frequently exposed by partial distal release of the overlying insertion of the medial collateral ligament (MCL). Biomechanically, any release of the MCL can increase knee laxity when valgus stress is applied. Clinically however, post-surgical valgus instability following HTO with partial MCL release is an uncommon complication. It is known that the open-wedge procedure can re-tention an intact MCL by the width of the base of the wedge. However, this re-tentioning effect is uncertain in small wedge sizes, preexisting medial compartment laxity and in the presence of a partially detached MCL. Considering the good clinical results after HTO, we hypothesized that a partial release of the superficial MCL for HTO does not play a crucial role in stabilizing valgus forces in the human knee. We therefore measured the effect of partial versus complete release of the superficial MCL to determine medial knee laxity represented by the amount of medial joint opening (MJO) under valgus stress in this human cadaver study. In ten knee pairs, the superficial and deep MCL were sectioned in sequence with a standardized abduction force of 15 kp with a Scheuba apparatus applied. In group 1 (5 knee pairs), the superficial MCL was completely sectioned whereas in group 2 (5 knee pairs), sectioning of the superficial MCL was restricted to the anterior border to mimic the surgical exposure for an HTO. To account for the interindividual variability of ligamentous laxity, only increments of MJO within knee pairs were statistically evaluated. Stress radiography did not reveal any significant differences in increments of MJO between knee pair specimens with complete versus partial release of the superficial MCL. We disproved our hypothesis and concluded that the anterior fibers of the superficial MCL do play a crucial role in maintaining valgus stability in this biomechanical setting. Therefore, the release of the superficial MCL for open-wedge HTO should be kept to a minimum to decrease the potential of late valgus instability. This is especially important in patients with small wedge sizes and medial compartment laxity since the anterior MCL fibers are the main contributor to medial joint stability and the re-tentioning effect of the remaining MCL fibers is presumably decreased. [ABSTRACT FROM AUTHOR]

Abstract: The collateral ligaments of the knee are important in maintaining knee stability. However, little data has been reported on the in vivo function of the collateral ligaments. The objective of this study was to investigate the change in length of different fiber bundles of the medial collateral ligament (MCL), deep fibers of the MCL (DMCL) and the lateral collateral ligament (LCL) during in vivo knee flexion. The knees of five healthy subjects were scanned using magnetic resonance imaging. These images were used to create three-dimensional models of the tibia and femur, including the insertions of the collateral ligaments. The MCL, DMCL, and LCL were each divided into three equal portions: an anterior bundle, a middle bundle and a posterior bundle. Next, the subjects were imaged from two orthogonal directions using fluoroscopy while performing a quasi-static lunge from 0° to 90° of flexion. The models and fluoroscopic images were then used to reproduce the in vivo motion of the knee. From these models, the length of each bundle of each ligament was measured as a function of flexion. The length of the anterior bundle of the MCL did not change significantly with flexion. The length of the posterior bundle of the MCL consistently decreased with flexion (p <0.05). The change in length of the DMCL with flexion was similar to the trend observed for the MCL. The length of the anterior bundle of the LCL increased with flexion and the length of the posterior bundle decreased with flexion. These data indicate that the collateral ligaments do not elongate uniformly as the knee is flexed, with different bundles becoming taut and slack. These data may help to provide a better understanding of the in vivo function of the collateral ligaments and be used to improve surgical reconstructions of the collateral ligaments. Furthermore, the data suggest that the different roles of various portions of the collateral ligaments along the flexion path should be considered before releasing the collateral ligaments during knee arthroplasty. [Copyright &y& Elsevier]