Persistent symptoms following non operative management in low grade MCL injury of the knee - The role of the deep MCL

Shedding light on the non-operative treatment of the forgotten side of the knee: rehabilitation of medial collateral ligament injuries-a systematic review

Objective

The purpose of this study was to review the current literature regarding the non-operative treatment of isolated medial collateral ligament (MCL) injuries.

Design

Systematic review, registered in the Open Science Framework (https://doi.org/10.17605/OSF.IO/E9CP4).

Data sources

The Embase, MEDLINE and PEDro databases were searched; last search was performed on December 2023.

Eligibility criteria

Peer-reviewed original reports from studies that included information about individuals who sustained an isolated MCL injury with non-surgical treatment as an intervention, or reports comparing surgical with non-surgical treatment were eligible for inclusion. Included reports were synthesised qualitatively. Risk of bias was assessed with the Risk of Bias Assessment tool for Non-randomized Studies. Certainty of evidence was determined using the Grading of Recommendations Assessment Development and Evaluation.

Results

A total of 26 reports (1912 patients) were included, of which 18 were published before the year 2000 and 8 after. No differences in non-operative treatment were reported between grade I and II injuries, where immediate weight bearing and ambulation were tolerated, and rehabilitation comprised different types of strengthening exercises with poorly reported details. Some reports used immobilisation with a brace as a treatment method, while others did not use any equipment. The use of a brace and duration of use was inconsistently reported.

Conclusion

There is substantial heterogeneity and lack of detail regarding the non-operative treatment of isolated MCL injuries. This should prompt researchers and clinicians to produce high-quality evidence studies on the promising non-operative treatment of isolated MCL injuries to aid in decision-making and guide rehabilitation after MCL injury.

Level of evidence

Level I, systematic review.

Isometry of anteromedial reconstructions mimicking the deep medial collateral ligament depends on the femoral insertion

PURPOSE

This study aimed to investigate the length change patterns of the native deep medial collateral ligament (dMCL) and potential anteromedial reconstructions (AMs) that might be added to a reconstruction of the superficial MCL (sMCL) to better understand the control of anteromedial rotatory instability (AMRI).

METHODS

Insertion points of the dMCL and potential AM reconstructions were marked with pins (tibial) and eyelets (femoral) in 11 cadaveric knee specimens. Length changes between the pins and eyelets were then tested using threads in a validated kinematics rig with muscle loading of the quadriceps and iliotibial tract. Between 0° and 100° knee flexion, length change pattern of the anterior, middle and posterior part of the dMCL and simulated AM reconstructions were analysed using a rotary encoder. Isometry was tested using the total strain range (TSR).

RESULTS

The tibiofemoral distance of the anterior dMCL part lengthened with flexion (+12.7% at 100°), whereas the posterior part slackened with flexion (-12.9% at 100°). The middle part behaved almost isometrically (maximum length: +2.8% at 100°). Depending on the femoral position within the sMCL footprint, AM reconstructions resulted in an increase in length as the knee flexed when a more centred position was used, irrespective of the tibial attachment position. Femoral positioning in the posterior aspect of the sMCL footprint exhibited <4% length change and was slightly less tight in flexion (min TSR = 3.6 ± 1.5%), irrespective of the tibial attachment position.

CONCLUSION

The length change behaviour of potential AM reconstructions in a functionally intact knee is mainly influenced by the position of the femoral attachment, with different tibial attachments having a minimal effect on length change. Surgeons performing AM reconstructions to control AMRI would be advised to choose a femoral graft position in the posterior part of the native sMCL attachment to optimise graft length change behaviour. Given the high frequency of MCL injuries, sufficient restoration of AMRI is essential in isolated and combined ligamentous knee injuries.

LEVEL OF EVIDENCE

There is no level of evidence as this study was an experimental laboratory study.

Lower extremity ultrasound-guided interventions: tendon, ligament, and plantar fascia

Lower extremity tendinopathy and soft tissue injury are common clinical problems that can cause significant disability. Ultrasound-guided minimally invasive treatments using orthobiologics and image-guided percutaneous treatments continue to gain relevance with an ever-growing body of literature. We review the indications, technique, risks, and benefits according to the literature of common ultrasound-guided interventions utilized in the lower extremities.

Heterotopic Mineralization of the Medial Collateral Ligament: Our Experience Treating Two Cases of Calcific Versus Ossific Lesions With Ultrasonic Vacuum Debridement

Chronic injury to the medial collateral ligament (MCL) is common following an acute knee injury. This case report presents two patients that failed to respond to conservative treatment with clinical evidence of an MCL injury and radiographic finding of a benign-appearing soft tissue lesion in the MCL. Calcified or ossified lesions have been described with chronic MCL injuries. Ossification and calcification of the MCL have been observed as potential causes of chronic MCL pain. Here, we detail the distinction between these two distinct intra-ligamentous heterotopic deposits and describe a novel treatment approach using ultrasonic percutaneous debridement, a technique that is typically reserved for tendinopathies. In both cases, pain improved, and they were able to return to their prior level of function.

Clinical Outcomes of Repair of Complete Detachment of Medial Collateral Ligament at the Tibial Insertion in Bilateral Total Knee Arthroplasty

Purpose

Complete detachment of the medial collateral ligament (MCL) may occur during medial release of total knee arthroplasty (TKA) in patients with severe varus knee osteoarthritis. This study was to determine functional and stability outcomes of repaired knee with complete detachment of MCL compared to those of contralateral nondetached MCL in patients with bilateral TKA.

Methods

Records of 1052 consecutive knees undergoing bilateral TKA from 2003 to 2015 were retrospectively reviewed. Of which, 45 patients were repaired for complete MCL detachment injury (2.1%) at tibial insertion in one side (repaired group). MCL was not detached in the contralateral side (control group). Clinical evaluation was performed preoperatively and at the final follow-up using KS and WOMAC scores between two groups. Similarly, stability was compared on a valgus stress radiograph between two groups.

Results

Two patients had insufficient data. Hence, 43 patients were included after a minimum of 5 years follow-up. There were no significant differences in terms of alignment and clinical outcomes between the two groups either preoperatively or at the final follow-up (p > 0.05). Radiographic stability also showed no differences between repaired and control groups in extension and 30° of flexion (p=0.208 and p=0.125).

Conclusions

For tibial detachment of the MCL during TKA, repair with suture anchor provided good clinical and stability results, similar to TKA without MCL injury. Therefore, repair with a suture anchor is a reliable method that provides good clinical and stability outcomes in patients with MCL injury during TKA.

Chronic Medial Collateral Ligament Sprain Treated With Percutaneous Ultrasonic Debridement: A Case Report

The medial collateral ligament (MCL) is the most commonly injured ligament of the knee. Most grade I and II injuries respond to conservative management, but symptoms persist in some patients. In these cases, treatment options are limited. Percutaneous ultrasonic debridement is increasingly being used for tendinopathy and fasciopathy refractory to conservative management, but this has not been reported as a treatment for ligament injury. Here, we present a case of a chronic grade II MCL sprain successfully treated with percutaneous ultrasonic debridement.

Musculoskeletal Injuries in Cross-Country Skiing

Cross-country skiing, one of the oldest forms of skiing, is enjoyed widely as a recreational activity and as a competitive sport. It is practiced in regions with snow-covered landscapes, particularly in the Nordic countries and with increasing popularity in non-Nordic countries of Europe as well as in the United States, Canada, Australia, and New Zealand, among others. Cross-country skiing is a fairly safe activity, and historically the risk of injury has been relatively low. However, advances in equipment development, together with increasing speeds, more demanding trails, and growing numbers of participants, have all contributed to a larger report of injuries, although still comparatively low versus other skiing modalities. Injuries in cross-country skiing can occur either after a single traumatic event or in the setting of chronic repetitive microtrauma (i.e., overuse injuries).

Return-to-Play Times and Player Performance After Medial Collateral Ligament Injury in Elite-Level European Soccer Players

Background:

Participation in elite-level soccer predisposes athletes to injuries of the medial collateral ligament (MCL), resulting in variable durations of time lost from sport.

Purpose:

To (1) determine the rate of return to play (RTP) and timing after MCL injuries, (2) investigate MCL reinjury incidence after RTP, and (3) evaluate the long-term effects of MCL injury on future performance.

Study Design:

Descriptive epidemiology study.

Methods:

Using publicly available records, we identified athletes who had sustained MCL injury between 2000 and 2016 across the 5 major European soccer leagues (English Premier League, Bundesliga, La Liga, Ligue 1, and Serie A). Injured athletes were matched to controls using demographic characteristics and performance metrics from the season before injury. We recorded injury severity, RTP rate, reinjury incidence, player characteristics associated with RTP within 2 seasons of injury, player availability, field time, and performance metrics during the 4 seasons after injury.

Results:

A total of 59 athletes sustained 61 MCL injuries, with 86% (51/59) of injuries classified as moderate to severe and surgical intervention performed in 14% (8/59) of athletes. After injury, athletes missed a median of 33 days (range, 3-259 days) and 4 games (range, 1-30 games). Overall, 71% (42/59) of athletes returned successfully at the same level, with multivariable regression demonstrating no athlete characteristic predictive of RTP. MCL reinjury was reported in 3% (2/59) of athletes. Midfielders demonstrated decreased field time after RTP when compared with controls (P < .05). No significant differences in player performance for any position were identified out to 4 seasons after injury. Injured athletes had a significantly higher rate of long-term retention (P < .001).

Conclusion:

MCL injuries resulted in a median loss of 33 days in elite European soccer athletes, with the majority of injuries treated nonoperatively. RTP remained high, and few athletes experienced reinjury. While midfielders demonstrated a significant decrease in field time after RTP, player performance and long-term retention were not compromised. Future studies are warranted to better understand athlete-specific and external variables predictive of MCL injury and reinjury, while evaluating treatment and rehabilitation protocols to minimize time lost and to optimize athlete safety and health.

Magnetic resonance imaging of medial collateral ligament avulsion fractures of the knee in children: a potentially underestimated injury

BACKGROUND

Literature regarding medial collateral ligament (MCL) injuries is focused on adults with superficial MCL disruptions. However, children follow different injury patterns, with avulsion fractures at ligament attachment sites occurring commonly. Such avulsions have not been characterized for pediatric MCL injuries.

OBJECTIVE

To elucidate imaging findings, and review management and outcomes of pediatric MCL avulsion fractures.

MATERIALS AND METHODS

We conducted a 10-year retrospective review of knee magnetic resonance (MR) imaging reports for patients younger than 16 years old diagnosed with acute MCL avulsion fracture. MR imaging was reviewed to confirm and characterize the components of the avulsion (perichondrium without or with cartilage, and/or bone) and to identify additional knee injuries. Radiographs, if available, from the time of injury were reviewed. Clinical management and patient outcomes were recorded.

RESULTS

Eighteen patients (13 boys, 5 girls) incurred an acute MCL avulsion fracture. All avulsions involved the deep MCL attachment: 17 meniscofemoral and 1 meniscotibial component. Two avulsions also included the superficial MCL attachment. Nine boys had non-osseous avulsions, all radiographically occult. All girls had radiographically apparent avulsions. Three girls and three boys sustained associated knee derangements, most commonly anterior cruciate ligament (ACL) injury (n=4). All MCL avulsions were initially treated conservatively; one child required subsequent surgery for ongoing pain.

CONCLUSION

Pediatric MCL avulsion fractures in this study uniformly involve the attachment of the deep MCL and can be entirely non-osseous, particularly in boys who lag in skeletal maturity, making these injuries radiographically occult. MR imaging may be required to recognize these avulsions, which can impact the duration of rest and knee bracing.

Isolierte Verletzung des tiefen Innenbands am Kniegelenk

Isolierte Rupturen des tiefen Innenbands am Kniegelenk (dMCL) werden meist im chronischen Stadium bzw. in Zusammenhang mit einer Verletzung des oberflächlichen Innenbands beschrieben. In diesem Beitrag wird über den Fall eines 15-jährigen Patienten berichtet, welcher sich nach einem Außenrotationstrauma des Kniegelenks in der Notaufnahme vorstellte. Die weiterführende Diagnostik zeigte eine isolierte Läsion des tiefen Innenbands. Erstmaßnahmen erfolgten mit Schonung, Hochlagerung, Salbenverbänden, oraler Schmerztherapie und einer Knieorthese. Fünf Wochen nach dem initialen Trauma war der Patient beschwerdefrei. Anhand der aktuellen Literatur wird ein Therapieschema der akuten bis chronischen Läsion des dMCL diskutiert.

Arthroscopic Primary Medial Collateral Ligament Repair With Suture Anchor

A medial collateral ligament (MCL) tear is common in cases of isolated injury or in those combined with anterior cruciate ligament injury. Although conservative treatment for an MCL tear is popular, some cases result in residual instability. Thus, the treatment approach of grade III MCL injury remains controversial. In this Technical Note, we present the technique of arthroscopic primary MCL repair with suture anchor. With this technique, proximal MCL injuries can be repaired with minimal invasion. This technique improves valgus stability and enables early rehabilitation, including range of motion and weight-bearing exercise.

[Osteochondral injury of the femoral insertion of the deep medial collateral ligament of the knee-is there a successful surgical treatment?]

Isolated ruptures of the deep portion of the medial collateral ligament (MCL) without clinical instability can mostly be treated conservatively with good clinical results. A 10-year-old girl was initially also treated conservatively. As symptoms of pain and limited range of motion were not resolved after 3 months of conservative treatment and although there were no signs of instability, it was decided to proceed with the surgical intervention. A small osteochondral fragment on the femoral insertion of the deep MCL (medial meniscofemoral ligament) was removed and the soft tissue portion of the ligament was reinserted in the anatomical footprint. The patient showed complete resolution of the pain and a full range of motion of the knee joint. At the last follow-up 18 months after surgery the patient was completely free of symptoms.

Medial collateral ligament (MCL) reconstruction results in improved medial stability: results from the Danish knee ligament reconstruction registry (DKRR)

PURPOSE

The aim of this study was to compare outcome data after isolated and combined (MCL) plus anterior cruciate ligament (ACL) reconstruction based on objective and subjective measures using data from the (DKRR). There are only a few small-sized case studies on outcomes after MCL reconstruction. MCL reconstruction was hypothesised to improve both objective and subjective outcomes.

METHODS

All patients who were registered in the DKRR between 2005 and 2016 (N = 25,281) and who underwent isolated ACL (n = 24,683), isolated MCL (n = 103) or combined MCL plus ACL (n = 495) reconstructions were retrospectively identified. Objective (valgus knee stability and sagittal knee laxity) and subjective (Knee Injury and Osteoarthritis Outcome Score (KOOS) and Tegner activity scale score) outcomes in these three cohorts were evaluated at the 1-year follow-up by comparing pre- and post-operative values.

RESULTS

Medial stability improved significantly pre- to post-operatively after both isolated MCL and combined MCL plus ACL reconstruction, with 26 (53%) and 195 (69%) of the patients, respectively, having normal valgus stability (0-2 mm laxity). Sagittal stability was similar after MCL plus ACL reconstruction and isolated ACL reconstruction (1.7 and 1.5 mm, respectively). At the 1-year follow-up, although the KOOS of the patients in the isolated MCL and combined MCL plus ACL reconstruction cohorts improved significantly, they were lower than those of the patients in the isolated ACL reconstruction cohort.

CONCLUSION

Both isolated MCL reconstruction and combined MCL plus ACL reconstruction resulted in significant and clinically relevant improvements in the subjective outcomes from pre-operative conditions to the 1-year follow-up. Valgus stability also improved significantly, with two-thirds of patients obtaining normal valgus stability after MCL reconstruction. Subjective outcomes were similar between isolated MCL reconstruction and combined MCL plus ACL reconstructions, but were poorer than isolated ACL reconstructions.

LEVEL OF EVIDENCE

Level III.

Autologous platelet-rich plasma therapy for refractory pain after low-grade medial collateral ligament injury

Objective

This study was performed to explore the effect of intra-articular injection of autologous platelet-rich plasma (PRP) on refractory pain after low-grade medial collateral ligament (MCL) injury.

Methods

In total, 52 patients with refractory pain after low-grade knee MCL injury were treated by intra-articular injection of autologous PRP. Every patient received a 5-mL intra-articular injection of autologous PRP once weekly for 3 weeks. All patients were evaluated by the International Knee Documentation Committee (IKDC) Subjective Knee Evaluation Form score before treatment and 1, 3, and 6 months after treatment. Magnetic resonance imaging of the knee was performed to observe the healing of the MCL injury 6 months after treatment.

Results

After one injection, the patients’ pain was greatly decreased and they stopped taking nonsteroidal anti-inflammatory drugs. The IKDC Subjective Knee Evaluation Form scores were significantly better after than before treatment; however, there were no significant differences among the various post-treatment time points. Magnetic resonance imaging showed that the low-grade MCL injury had completely healed, and no edema was present around the MCL.

Conclusions

Intra-articular injection of autologous PRP is an effective treatment for refractory pain after low-grade MCL injury.

Superficial and Deep Medial Collateral Ligament Reconstruction for Chronic Medial Instability of the Knee

There are several surgical techniques for medial collateral ligament reconstruction, including anatomic or nonanatomic medial knee reconstruction. Although the medial collateral ligament consists of the superficial medial collateral ligament (sMCL) and deep medial collateral ligament (dMCL), surgical procedures have only been described for reconstruction of the sMCL alone or reconstruction of the sMCL and posterior oblique ligament. The dMCL assists the knee in rotational stability, primarily in extension, moving into early flexion. We describe sMCL and dMCL reconstruction with semitendinosus and gracilis autografts using adjustable-length loop suspensory fixation devices for tibial fixation. By use of our technique, it is possible to provide good stability and satisfactory results for medial instability of the knee.

An Autologous Leukocyte-Reduced Platelet-Rich Plasma Therapy for Chronic Injury of the Medial Collateral Ligament in the Knee: A Report of 3 Successful Cases

Some patients complain of chronic persistent medial knee pain after isolated low-grade injuries of medial collateral ligaments (MCL). These injuries often respond to various conservative treatments but insufficient healing of ligaments is believed to be responsible for symptoms in this group of patients. We report on successful treatment of chronically symptomatic MCL injuries in 3 patients using autologous leukocyte-reduced platelet-rich plasma (PRP) injections. There were 3 men with a mean age of 39.3 years and a mean disease duration of 10 months. Magnetic resonance imaging showed discontinuities of superficial layers and thickness of deep layers in the proximal MCL. After PRP injections, all cases returned to their sport activities at a previous level as without symptoms, and complete healing of proximal ligaments was identified on magnetic resonance images. The outcomes indicated that PRP injections led to successful repair for chronic injuries of MCL in knees.

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.

Evaluation of Knee Pain in Athletes: A Radiologist's Perspective

Lower limb injuries account for most of all injuries suffered by athletes and the knee joint accounts for over half of these. The etiology of knee pain is multifactorial; a good history focusing on the mechanism of injury and the chronicity of pain is extremely useful in correlating with radiologic findings and establishing a clinically meaningful diagnosis. This review article will discuss several important and common causes of acute and chronic knee pain in athletes, focusing on their mechanism of injury and site of pain as well as their salient imaging findings.

High-volume image-guided injection for recalcitrant medial collateral ligament injuries of the knee

AIM

To evaluate the effectiveness of a novel injection technique in the management of recalcitrant medial collateral ligament (MCL) injuries of the knee.

MATERIALS AND METHODS

The injection, comprising 10 ml local anaesthetic with 25-50 mg hydrocortisone, is directed beneath the periosteal attachment of the MCL. Twenty-eight patients who received the intervention were asked to complete a questionnaire, a visual analogue scale (VAS) and the International Knee Documentation Committee (IKDC) subjective knee form to quantify symptoms pre-injection and at follow-up. Data were assessed using descriptive statistics. Further analysis was conducted using the Wilcoxon signed-rank test and Fisher's exact test.

RESULTS

Sixty-eight percent (n = 19) of patients responded. Three patients were excluded according to the exclusion criteria. Of those studied, 37.5% (n = 6) were professional athletes. At follow-up, patients reported a mean improvement on the VAS of 75.5% (SD = 23.6). There was a significant improvement in IKDC scores (mean difference 42%, SD = 14.2) pre- and post-injection (Wilcoxon signed-rank test, p < 0.001). No residual symptoms were reported by 50% (n = 8) of patients, and a further 37.5% (n = 6) of patients had improved. Of those patients who played sport, two-thirds (n = 10) had returned to their previous level of sport at follow-up, including all of the professional athletes.

CONCLUSION

Periosteal high-volume image-guided injection is a useful treatment for recalcitrant MCL injury. Results are encouraging, particularly amongst the professional athletes studied.

Consideration of growth factors and bio-scaffolds for treatment of combined grade II MCL and ACL injury

The literature suggests that a Grade II medial collateral ligament (MCL) injury in combination with anterior cruciate ligament (ACL) injury will heal naturally and not compromise patient outcome following ACL reconstruction. Evidence based on bone-patella tendon-bone autograft use is stronger than evidence supporting anatomically placed soft tissue graft use. Current ACL reconstruction practices make greater use of soft tissue grafts, differing fixation methods, and anatomically lower placement on the inner wall of the lateral femoral condyle. Anatomical graft placement aligns the femoral bone tunnel more directly with valgus knee loading forces. Differences in the soft tissue graft-bone tunnel integration and ligamentization timetable following ACL reconstruction also increase concerns regarding residual Grade II MCL laxity and functional deficiency during accelerated functional rehabilitation. MCL dysfunction may increase susceptibility to early ACL graft slippage, elongation, outright failure, and medial femoral condyle lift-off with valgus knee loading. This concept paper discusses the potential role of growth factors and bio-scaffolds for improving Grade II MCL injury healing and mechanical integrity when the injury occurs in combination with an ACL injury that is reconstructed with a soft tissue graft and an anatomical surgical approach.

Fractures of the distal phalanx and associated soft tissue and osseous abnormalities in 22 horses with ossified sclerotic ungual cartilages diagnosed with magnetic resonance imaging

Ungual cartilage ossification in the forelimb is a common finding in horses. Subtle abnormalities associated with the ungual cartilages can be difficult to identify on radiographs. Magnetic resonance (MR) imaging findings of 22 horses (23 forelimbs) with a fracture of the distal phalanx and ossified ungual cartilage were characterized and graded. All horses had a forelimb fracture. Eleven involved a left forelimb (seven medial; four lateral), and 12 involved a right forelimb (five medial; seven lateral). All fractures were nonarticular, simple in configuration, and nondisplaced. The fractures were oriented in an axial proximal to abaxial distal and palmar to dorsal direction, and extended from the base of the ossified ungual cartilage into the distal phalanx. The fracture involved the fossa of the collateral ligament on the distal phalanx in 17 of 23 limbs. The palmar process and ossified ungual cartilage was abnormally mineralized in all horses. Ligaments and soft tissues adjacent to the ossified ungual cartilages were affected in all horses. The routine site of fracture in this study at the base of the ossified ungual cartilage extending into the distal phalanx suggests a biomechanical cause or focal stress point from cycling. The ligamentous structures associated with the ungual cartilages were often affected, showed altered signal intensity as well as enlargement and were thought to be contributing to the lameness. In conclusion, ossified ungual cartilages may lead to fracture of the palmar process of the distal phalanx and injury of the ungual cartilage ligaments.

In vivo length patterns of the medial collateral ligament during the stance phase of gait

PURPOSE

The function of the medial collateral ligament (MCL) during gait has not been investigated. Our objective was to measure the kinematics of the medial collateral ligament during the stance phase of gait on a treadmill using a combined dual fluoroscopic imaging system (DFIS) and MRI technique.

METHODS

Three-dimensional models of the knee were constructed using magnetic resonance images of 7 healthy human knees. The contours of insertion areas of the superficial MCL (sMCL) and deep MCL (dMCL) on the femur and tibia were constructed using the coronal plane MR images of each knee. Both the sMCL and the dMCL were separated into 3 portions: the anterior, mid, and posterior bundles. The relative elongation of the bundles was calculated using the bundle length at heel strike (or 0% of the stance phase) as a reference.

RESULTS

The lengths of the anterior bundles were positively correlated with the knee flexion angle. The mid-bundles of the sMCL and dMCL were found to function similarly in trend with the anterior bundles during the stance phase of the gait and their lengths had weak correlations with the knee flexion angles. The elongations of the posterior bundles of sMCL and dMCL were peaked at mid-stance and terminal extension/pre-swing stance phase. The lengths of the posterior bundles were negatively correlated with the knee flexion during the stance phase.

CONCLUSION

The data of this study demonstrated that the anterior and posterior bundles of the sMCL and dMCL have a reciprocal function during the stance phase of gait. This data provide insight into the function of the MCL and a normal reference for the study of physiology and pathology of the MCL. The data may be useful in designing reconstruction techniques to better reproduce the native biomechanical behavior of the MCL.

LEVEL OF EVIDENCE

IV.

Anomalous fiber realignment during tensile loading of the rat facet capsular ligament identifies mechanically induced damage and physiological dysfunction

Many pathophysiological phenomena are associated with soft tissue loading that does not produce visible damage or tissue failure. As such, there is an unexplained disconnect between tissue injury and detectable structural damage during loading. This study investigated the collagen fiber kinematics of the rat facet capsular ligament to identify the onset of subfailure damage during tensile loading conditions that are known to induce pain. Quantitative polarized light imaging was used to determine the collagen fiber orientation in the capsular ligament (n=7) under tension, and an alignment vector correlation measurement was employed to identify local anomalous fiber realignment during loading. During the initial portion of loading when tissue stiffness was increasing, anomalous realignment was more likely to be detected than mechanical evidence of structural damage, and as a result, anomalous fiber realignment was identified significantly (p=0.004) before gross failure. The occurrence of anomalous fiber realignment was significantly associated (p=0.013) with a decrease in tangent stiffness during loading (ligament yield), suggesting this optical metric may be associated with a loss of structural integrity. The presence of localized anomalous realignment during subfailure loading in this tissue may explain the development of laxity, collagen fiber disorganization, and persistent pain previously reported for facet joint distractions comparable to that required for anomalous realignment. These optical data, together with the literature, suggest that mechanically induced tissue damage may occur in the absence of any macroscopic or mechanical evidence of failure and may produce local pathology and pain.

Vector correlation technique for pixel-wise detection of collagen fiber realignment during injurious tensile loading

Excessive soft tissue loading can produce adverse structural and physiological changes in the absence of any visible tissue rupture. However, image-based analysis techniques to assess microstructural changes during loading without any visible rupture remain undeveloped. Quantitative polarized light imaging (QPLI) can generate spatial maps of collagen fiber alignment during loading with high temporal resolution and can provide a useful technique to measure microstructural responses. While collagen fibers normally realign in the direction that tissue is loaded, rapid, atypical fiber realignment during loading may be associated with the response of a local collagenous network to fiber failure. A vector correlation technique was developed to detect this atypical fiber realignment using QPLI and mechanical data collected from human facet capsular ligaments (n=16) loaded until visible rupture. Initial detection of anomalous realignment coincided with a measurable decrease in the tissue stiffness in every specimen and occurred at significantly lower strains than those at visible rupture (p<0.004), suggesting this technique may be sensitive to a loss of microstructural integrity. The spatial location of anomalous realignment was significantly associated with regions where visible rupture developed (p<0.001). This analysis technique provides a foundation to identify regional differences in soft tissue injury tolerances and relevant mechanical thresholds.