Tram-track appearance of the posterior cruciate ligament (PCL): correlations with mucoid degeneration, ligamentous stability, and differentiation from PCL tears

Do the Clinical and Radiological Features of Knees with Mucoid Degeneration of the Anterior Cruciate Ligament Differ According to Knee Osteoarthritis Status?

Background

The etiology and pathology of mucoid degeneration of the anterior cruciate ligament (MD-ACL) remain poorly understood. MD-ACL may be associated with knee osteoarthritis (OA) or a mechanism other than OA. This study evaluated the radiological differences between knees with MD-ACL and those with a normal ACL and compared the clinical and radiological features of knees with MD-ACL according to the knee OA status.

Methods

This retrospective study compared the radiological features of the intercondylar notch width index (NWI) and posterior tibial slope (PTS) of 67 MD-ACL patients (MD group) and 67 age-, sex-, and OA grade-matched patients with a normal ACL (control group). During the subgroup analysis, MD-ACL patients were divided into the non-OA subgroup (n = 41) and OA subgroup (n = 26). The pain location and characteristics of the knee, PTS, and NWI were compared between these subgroups.

Results

Compared to the control group, the MD group had a lower NWI (0.26 ± 0.03 vs. 0.28 ± 0.01, p < 0.001) and a larger PTS (11.3° ± 3.0° vs. 9.2° ± 2.5°, p < 0.001). During the subgroup analysis, the most common pain locations were the posterior and medial aspects of the knee in the non-OA subgroup (43.9%) and OA subgroup (53.8%), respectively. Pain on terminal flexion was the most common pain characteristic in both subgroups (non-OA subgroup, 73.1%; OA subgroup, 53.8%). The PTS was not different between subgroups (11.7° ± 3.2° in the non-OA subgroup vs. 10.6° ± 2.7° in the OA subgroup; p = 0.159). However, the non-OA subgroup had a lower NWI than the OA subgroup (0.25 ± 0.03 vs. 0.28 ± 0.02, p = 0.001).

Conclusions

Patients with MD-ACL had a lower NWI and a larger PTS than patients with a normal ACL. Furthermore, the clinical and radiological features of MD-ACL differed according to the knee OA status. A narrow intercondylar notch may be more closely associated with the development of MD-ACL without OA.

Nutrient vessel dysfunction can contribute to mucoid degeneration of the posterior cruciate ligament coexisting with lipoma arborescens: A case study

INTRODUCTION

With the rapid improvement of magnetic resonance imaging (MRI), mucoid degeneration (MD) of the anterior cruciate ligament (MD-ACL) has become an established disease entity and mechanical factors, such as increased posterior tibial tilt and intercondylar notch impingement, have been proposed. However, symptomatic MD of the posterior cruciate ligament (MD-PCL) remains an orphan disease without any established etiology.

PRESENTATION OF CASE

A man in his 60s exhibited restricted range of motion with knee pain. MRI revealed PCL enlargement with high-signal intensity and tram-track appearance on T2-weighted sagittal images and lipoma arborescens (LA) in the suprapatellar pouch. On gadolinium-enhanced MRI, the distal PCL was not contrasted. Arthroscopy revealed an almost normal expanded appearance with partial loss of the envelope synovium. Debulking operation was performed. Pathological findings revealed intravascular thrombus formation in early lesions of MD, and intraligamentous vascular degeneration and severity of MD were proportional.

DISCUSSION

ACL is susceptible to mechanical external forces from surrounding tissues because of its anatomical features that induce protease expression, resulting in MD-ACL with denatured large aggregating proteoglycans deposition. Conversely, occlusion of nutrient vessels within the ligament was observed in this case of MD-PCL. Coexisting LA likely provoked an inflammatory response with hypercoagulability, resulting in thromboembolism of the envelope synovial nutrient vessel.

CONCLUSION

MD-CL is a disease entity comprising multiple pathologies. Although symptomatic MD-ACL is mainly caused by mechanical factors with a relatively high morbidity rate, nutrient vessel dysfunction can contribute to symptomatic MD-PCL with coexisting LA in middle-aged adults with an extremely low morbidity rate.

The use of ultrasonography as an effective screening tool for chronic posterior cruciate ligament injuries

PURPOSE

We aimed to explore the applicability and validity of ultrasonography for diagnosing chronic posterior cruciate ligament (PCL) injuries.

METHODS

PCL thickness was measured at 2 cm proximal to the tibia insertion site. Using the same ultrasonography image, the angle tangent to the PCL from the tibia insertion site was also measured. These data were analyzed by plotting the receiver operating curve (ROC), and the sensitivity and specificity were calculated according to the optimal cut-off point. Ultrasonography data from the PCLinjured knee were compared with those from the contralateral uninjured knee of the same patient.

RESULTS

Twelve men and six women, with a mean age of 28.8 ± 14.0 years, were included in this study. The mean time from injury to medical examination was 10.0 ± 6.7 months. The mean thickness of the PCL was 8.1 ± 1.9 mm on the affected side and 5.8 ± 1.2 mm on the uninjured side, with the affected side being significantly thicker. ROC analysis revealed that the optimal cut-off value for the thickness of chronic PCL injuries was 6.5 mm (sensitivity 83.3%, specificity 77.8%, area under the curve [AUC] = 0.87). The optimal cut-off value for the angle was 20° (sensitivity 88.9%, specificity 94.4%, AUC = 0.96).

CONCLUSION

Ultrasonography is useful as a screening tool for chronic PCL injuries. The optimal cut-off point was 6.5 mm for thickness and 20° for angle.

LEVEL OF EVIDENCE

IV.

Ancillary findings in distinguishing between anterior cruciate ligament mucoid degeneration and sprain on MRI: a practical approach

BACKGROUND

Imaging findings of both anterior cruciate ligament (ACL) sprain and mucoid degeneration overlap in some cases, which may cause errors in magnetic resonance imaging (MRI) evaluation.

PURPOSE

To determine the ancillary findings on MRI in distinguishing between ACL sprain and mucoid degeneration, and also to obtain a diagnostic scheme.

MATERIAL AND METHODS

MRI scans of 77 patients with ACL mucoid degeneration and 77 cases with ACL sprain were retrospectively evaluated to compare with regard to parameters of age, sex, side, the status of posterior cruciate ligament - medial collateral ligament - lateral collateral ligament, bone marrow edema, intraosseous cyst, subchondral sclerosis, chondromalacia, meniscus tear, effusion, and osteochondral body. A decision tree algorithm was created to predict pathology in ACL, whether it was a sprain or mucoid degeneration.

RESULTS

The prevalence of female sex, femoral intraosseous cyst, tibial intraosseous cyst, subchondral sclerosis, femoral chondromalacia, tibial chondromalacia, medial meniscus tear, and lateral meniscus tear were significantly higher in the ACL mucoid degeneration group (P < 0.001, P = 0.016, P < 0.001, P = 0.003, P < 0.001, P < 0.001, P < 0.001, and P < 0.001, respectively). The probability of being mucoid degeneration increased 41.2 times (95% confidence interval [CI] = 5.296-321.132) in cases with tibial intraosseous cyst and increased 1.05 times (95% CI = 1.010-1.080) with each one-year increase in age (P < 0.001 and P = 0.011, respectively). The decision tree algorithm had an overall accuracy of 79.2%.

CONCLUSION

Ancillary findings are helpful in the diagnosis of suspicious cases for ACL mucoid degeneration and ACL sprain. The decision tree algorithm offers a practical and successful approach to this issue.

Association between magnetic resonance imaging characteristics and pathological findings in entire posterior cruciate ligament with mucoid degeneration

Magnetic resonance imaging (MRI) findings of a tram-track appearance and celery stalk appearance in mucoid degeneration of the cruciate ligament are valuable; however, their pathological basis is unclear. Because these appearances are generally seen throughout the entire ligament, the association between MRI findings and pathological findings must be verified in specimens of the whole degenerated ligament, including the ligamentous attachments to bone. We herein report two cases of mucoid degeneration of the posterior cruciate ligament with osteoarthritis of the knee requiring total knee arthroplasty. The entire degenerated ligament, including the ligamentous attachments to bone, was removed and pathologically evaluated. On pathological examination, the central portion of the lesion showed typical mucoid degeneration, whereas the marginal and adherent portions showed normal ligament tissue, consistent with a tram-track appearance on T2-weighted MRI. The fibrous normal ligament tissues in the longitudinal direction in regions of mucoid degeneration were consistent with a celery stalk appearance on T2-weighted MRI. No mucoid degeneration was found in the attachment area. The tram-track appearance and celery stalk appearance of mucoid degeneration on MRI can be explained by the pathological findings.

Mucoid degeneration of the posterior cruciate ligament in a college soccer player: a case report

BACKGROUND

To the best of our knowledge, arthroscopic treatment for symptomatic mucoid degeneration of the posterior cruciate ligament in young athletes has not been reported before.

CASE PRESENTATION

An 18-year-old Asian male college soccer player presented with a 3-month history of right knee pain without episodes of trauma. Despite conservative treatment over the preceding 3 months, his symptoms persisted. Physical examination of the right knee revealed full range of motion, though posterior knee pain was induced when the knee approached full flexion. On ligament examination, posterior sagging and Lachman test were negative, and no clinical finding indicative of ligament insufficiency was noted. Magnetic resonance imaging showed a diffusely thickened posterior cruciate ligament with increased signal intensity on the T2-weighted sequence. A few intact fibers were observed with continuous margin from origin to insertion. Based on the patient's history and the magnetic resonance imaging findings, we suspected mucoid degeneration of the posterior cruciate ligament as the cause of the patient's symptoms. Since conservative treatment had failed to relieve the symptoms, arthroscopic treatment was indicated. Arthroscopic examination revealed yellowish crumbly tissues along the thickened posterior cruciate ligament. Tension and bulk of the posterior cruciate ligament were well preserved. Curettage of degenerative tissue and decompression of the posterior cruciate ligament resulted in symptom relief without instability of the knee joint. The patient returned to play at 3 months. At 12 months, postoperative magnetic resonance imaging showed no evidence of recurrence and indicated that the remaining posterior cruciate ligament was thicker than before the surgery. At 2 years follow-up, the patient remained asymptomatic and could play soccer at the same level as before the onset of pain.

CONCLUSIONS

Arthroscopic decompression of the posterior cruciate ligament may relieve knee pain and facilitate early return to play with good functional results.

Imaging Review of the Posterior Cruciate Ligament

Posterior cruciate ligament (PCL) injuries can often be missed on physical examination, especially in multiligament knee injuries. Therefore, a comprehensive approach to imaging the PCL should be implemented whenever history and examination findings indicate relative risk. Radiography, including a posterior-stress view, and magnetic resonance imaging, when available, provide consistently accurate diagnosis of PCL pathology and common knee comorbidities. Computed tomography and ultrasonography can be useful modalities with potential advantages with respect to availability and access, specific comorbidities, and/or cost-effectiveness.

Magnetic resonance imaging of the knee

Knee pain is frequently seen in patients of all ages, with a wide range of possible aetiologies. Magnetic resonance imaging (MRI) of the knee is a common diagnostic examination performed for detecting and characterising acute and chronic internal derangement injuries of the knee and helps guide patient management. This article reviews the current clinical practice of MRI evaluation and interpretation of meniscal, ligamentous, cartilaginous, and synovial disorders within the knee that are commonly encountered.

Intraarticular Ligament Degeneration Is Interrelated with Cartilage and Bone Destruction in Osteoarthritis

Osteoarthritis (OA) induces inflammation and degeneration of all joint components including cartilage, joint capsule, bone and bone marrow, and ligaments. Particularly intraarticular ligaments, which connect the articulating bones such as the anterior cruciate ligament (ACL) and meniscotibial ligaments, fixing the fibrocartilaginous menisci to the tibial bone, are prone to the inflamed joint milieu in OA. However, the pathogenesis of ligament degeneration on the cellular level, most likely triggered by OA associated inflammation, remains poorly understood. Hence, this review sheds light into the intimate interrelation between ligament degeneration, synovitis, joint cartilage degradation, and dysbalanced subchondral bone remodeling. Various features of ligament degeneration accompanying joint cartilage degradation have been reported including chondroid metaplasia, cyst formation, heterotopic ossification, and mucoid and fatty degenerations. The entheses of ligaments, fixing ligaments to the subchondral bone, possibly influence the localization of subchondral bone lesions. The transforming growth factor (TGF)β/bone morphogenetic (BMP) pathway could present a link between degeneration of the osteochondral unit and ligaments with misrouted stem cell differentiation as one likely reason for ligament degeneration, but less studied pathways such as complement activation could also contribute to inflammation. Facilitation of OA progression by changed biomechanics of degenerated ligaments should be addressed in more detail in the future.

Quantitative mapping of acute and chronic PCL pathology with 3 T MRI: a prospectively enrolled patient cohort

Background

The diagnosis of incomplete acute and chronic posterior cruciate ligament (PCL) tears can be challenging with conventional magnetic resonance (MR) imaging, particularly for injuries in which the ligament appears continuous as occurs with chronic PCL tears that have scarred in continuity. Quantitative mapping from MR imaging may provide additional useful diagnostic information in these cases. The purpose of this study was to assess the feasibility of quantifying transverse relaxation time (T2) mapping values at 3 Tesla (T) in a prospectively enrolled patient cohort with chronic PCL tears.

Methods

Twelve subjects with acute or chronic functionally torn PCL, confirmed on clinical exam and posterior knee stress radiographs (with 8 mm or more of increased posterior tibial translation), were enrolled prospectively over a span of 4 years (age: 28–52 years, injury occurred 2 weeks to 15 years prior). Unilateral knee MR images were acquired at 3 T, including a multi-echo spin-echo T2 mapping scan in the sagittal plane. For the six subjects with a continuous PCL on MR imaging the PCL was manually segmented and divided into proximal, mid and distal thirds. Summary statistics for T2 values in each third of the ligament were compiled.

Results

Across the six patient subjects with a continuous ligament, the mean T2 for the entire PCL was 36 ± 9 ms, with the highest T2 values found in the proximal third (proximal: 41 ms, mid 30 ms, distal 37 ms). The T2 values for the entire PCL and for the proximal third subregion were higher than those recently published for asymptomatic volunteers (entire posterior cruciate ligament: 31 ± 5 ms, proximal: 30 ms, mid: 29 ms, distal: 37 ms) with similar methodology.

Conclusion

Mean T2 values were quantified for acute and chronic PCL tears in this prospectively enrolled patient cohort and were higher than those reported for asymptomatic volunteers. This novel approach of using quantitative mapping to highlight injured areas of the posterior cruciate ligament has potential to provide additional diagnostic information in the challenging case of a suspected posterior cruciate ligament tear which appears continuous, including chronic tears that have scarred in continuity and may appear intact on conventional magnetic resonance imaging.

Imaging of Athletic Injuries of Knee Ligaments and Menisci: Sports Imaging Series

Acute knee injuries are a common source of morbidity in athletes and if overlooked may result in chronic functional impairment. Magnetic resonance (MR) imaging of the knee has become the most commonly performed musculoskeletal MR examination and is an indispensable tool in the appropriate management of the injured athlete. Meniscal and ligamentous tearing are the most frequent indications for surgical intervention in sports injuries and an understanding of the anatomy, biomechanics, mechanisms of injury, and patterns of injury are all critical to accurate diagnosis and appropriate management. These will be discussed in reference to meniscal tears and injuries of the cruciate ligaments as well as injuries of the posterolateral and posteromedial corners of the knee. (©) RSNA, 2016.

Magnetic resonance imaging of degenerative changes of the posterior cruciate ligament

Background Mucoid degeneration and ganglia reflect a continuum of degenerative changes within the posterior cruciate ligament (PCL). Purpose To assess the prevalence of and radiologists' familiarity with PCL mucoid degeneration and ganglia. Material and Methods Knee magnetic resonance imaging (MRI) from July 2013 to June 2015, excluding patients who had a preceding trauma or MRI findings indicative of a prior injury, were retrospectively reviewed, with the specific request to assess degenerative changes of the PCL, by the same musculoskeletal radiologists who previously reported these examinations, and one fellow. Results A total of 692 patients entered this study. The radiologists and the fellow together identified mucoid degeneration in 34 patients (4.9%), ganglia in 14 patients (2.0%), and both in four patients (0.6%). Several patterns of PCL mucoid degeneration were identified: diffuse thickening in seven patients, partial thickening in 16 (four associated with a ganglion), longitudinal intraligamentous PCL signal-intensity abnormalities resembling a "tram track" in 15. In all cases there was increased signal intensity on fluid-sensitive sequences. In the previous reports, only three cases of PCL mucoid degeneration out of 38 (7.9%) were described, with intraligamentous PCL signal-intensity abnormalities. In the reports of the patients with degeneration and ganglia, only ganglia were described. In the previous reports, ganglia were correctly diagnosed. Conclusion Mucoid degeneration of the PCL is much more common than previously assumed and is underestimated by radiologists.

Mucoid Degeneration of Posterior Cruciate Ligament with Secondary Impingement of Anterior Cruciate Ligament: A Rare Case Report

Introduction:

Mucoid degeneration of cruciate ligament is well known entity, but symptomatic lesions are rare. It is even rarer to find a symptomatic posterior cruciate ligament mucoid degeneration than anterior cruciate ligament.

Case Report:

A 65-years-old female presented to our hospital complaining of pain in right knee joint on terminal extension since 6 months. On clinical examination, there was a flexion deformity of 5 degree and a further flexion of 150 degree with mild pain exacerbated by extension. MRI of the right knee joint showed a diffusely thickened posterior cruciate ligament (PCL) with increased intra ligamentous signal intensity on T2-weighted images. The arthroscopic findings of grossly thickened PCL with a yellowish hue are characteristic and the PCL was filled with a yellowish substance. We excised the yellowish substance from the PCL as precisely as possible not to damage the remaining PCL fiber (Limited Debulking). We did notchplasty of lateral wall and roof to accommodate the Anterior Cruciate Ligament and avoid impingement.

Conclusion:

Posterior cruciate ligament may enlarge significantly and may push the Anterior Cruciate Ligament in the notch and may lead to the anterior cruciate ligament (ACL) impingement symptoms. Partial Debulking of Posterior Cruciate Ligament and notchplasty is effective treatment with immediate postoperative pain relief and good functional results.

Cysts of the anterior horn lateral meniscus and the ACL: is there a relationship?

OBJECTIVE

Parameniscal cysts have a very high association with meniscal tears in all locations except the anterior horn lateral meniscus (AHLM). The common insertion of the anterior cruciate ligament (ACL) and the AHLM root may provide a pathway for disease. The purpose of our study was to determine if cysts of the ACL are the origin of cysts adjacent to the AHLM.

MATERIALS AND METHODS

Radiology reports of all magnetic resonance (MR) examinations of the knee over a 7-year period were searched for "cyst", "ganglion", and "ganglia". Two fellowship-trained musculoskeletal radiologists independently reviewed those MR examinations reported to have a possible cyst of the AHLM and/or the ACL. The study group consisted of those patients with a cyst located adjacent to the AHLM but no meniscal tear of the adjacent meniscus. The ACL in each of these patients was evaluated for the presence of a cyst. Comparison with age- and gender-matched controls was performed.

RESULTS

Of 708 cases that contained the word "cyst", "ganglion", or "ganglia", 121 reports indicated a possible cyst of the ACL or AHLM. Twelve individuals had a cyst located adjacent to the AHLM with no meniscal tear. Six (50%) of these individuals had a cyst of the ACL; no ACL cysts were identified in the control group (p = 0.014). Interreader agreement for AHLM parameniscal cysts and AHLM tears was substantial.

CONCLUSIONS

Our results suggest that cysts adjacent to the AHLM may in part be explained by cysts or ganglia of the ACL.

MR imaging of cruciate ligaments

Cruciate ligament injuries, and in particular injuries of the anterior cruciate ligament (ACL), are the most commonly reconstructed ligamentous injuries of the knee. As such, accurate preoperative diagnosis is essential in optimal management of patients with cruciate ligament injuries. This article reviews the anatomy and biomechanics of the ACL and posterior cruciate ligament (PCL) and describes the magnetic resonance (MR) imaging appearances of complete and partial tears. Normal postoperative appearances of ACL and PCL reconstructions as well as MR imaging features of postoperative complications will also be reviewed.