|Year : 2014 | Volume
| Issue : 2 | Page : 160-165
Role of magnetic resonance imaging in the evaluation of articular cartilage in painful knee joint
Digish Shah, Satish Naware, Shoubhi Bhatnagar, Vilas M Kulkarni
Department of Radio-Diagnosis, Padmashree Dr. D. Y. Patil Medical College, Hospital and Research Centre, Dr. D. Y. Patil Vidyapeeth, Pimpri, Pune, Maharashtra, India
|Date of Web Publication||4-Feb-2014|
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Source of Support: None, Conflict of Interest: None
Aim: The aim of this study was to determine the role of the magnetic resonance imaging (MRI) in patients with atraumatic knee pain. Background and Objectives: Knee pain is one of the most common problems faced by people from time immemorial. There is a wide range of disease ranging from traumatic to degenerative causing knee pain in which articular cartilage is involved. Over the past 15 years, MRI has become the premier, first-line imaging study that should be performed in the evaluation of the painful knee in particular in tears of menisci, cruciate and collateral ligaments, osteochondral abnormalities (chondromalacia, osteoarthritis and osteochondral defects), synovial cysts and bone bruises. MRI, by virtue of its superior soft-tissue contrast, lack of ionizing radiation and multiplanar capabilities, is superior to more conventional techniques for the evaluation of articular cartilage. Materials and Methods: A prospective study was carried out on 150 patients in the Department of Radio-diagnosis, Padmashree Dr. D. Y. Patil Medical College, Hospital and Research Centre, Pimpri, Pune over a period of 2 years from June 2011 to May 2013. Patients having fracture or dislocations of the knee joint were also excluded from the study. Detailed clinical history, physical and systemic examination findings of all patients were noted in addition to the laboratory investigations. All patients were subjected to radiograph of knee anterior-posterior and lateral view. MRI was performed with Siemens 1.5 Tesla MAGNETOM Avanto machine. Results: In our study of 150 patients with knee pain, articular cartilage defect was found in 90 patients (60%). Out of 90 patients with articular cartilage defect, 30 patients (20%) had full thickness cartilage defects. Subchondral marrow edema was seen beneath 30 patients (20%) with articular cartilage defects. 32 patients (21.1%) had a complex or macerated meniscal tear. Complete anterior cruciate ligament tear was found in seven patients. Joint effusions were detected in 70% (105) of the knees. Large Baker cysts were observed in 6.1% of the knees. Conclusion: In conclusion, individual with acute or chronic knee pain without any definite history of trauma should be subjected to MRI study of the knee provided radiographs are non-informative or non-diagnostic. The study not only outlines the tendons, ligament and cartilage status, but also demonstrates subtle underlying bony pathologies causative for patient complaints.
Keywords: Articular cartilage, knee pain, magnetic resonance imaging
|How to cite this article:|
Shah D, Naware S, Bhatnagar S, Kulkarni VM. Role of magnetic resonance imaging in the evaluation of articular cartilage in painful knee joint. Med J DY Patil Univ 2014;7:160-5
| Introduction|| |
Knee pain is one of the most common problems faced by people. The overall prevalence of knee pain in the population is approximately 19%.  The incidence increases steadily with age. There is a wide range of disease ranging from traumatic to degenerative causing knee pain in which articular cartilage is involved. The degree of involvement of articular cartilage in various conditions causing knee pain cannot be assessed clinically; hence diagnostic radiology is of paramount importance.
X-rays only show the bone injuries and therefore are not helpful in diagnosing articular cartilage in the early stage. Lesions appear as a line of demarcation around the small area of bone if the lesion is still attached or a loose body or crater if separation has occurred.  Ultrasonography of knee helps to evaluate the synovium, fluid, femoral cartilage and loose bodies. There are two major drawbacks with this technique, first is the long learning curve and the other is that there is very little tissue differentiation when it comes to the acoustic properties of various structures. 
In recent decades, magnetic resonance imaging (MRI) has become the most important modality for assessment of pathologic changes in knee cartilage, in both clinical and research environments. One of the major advantages of MRI is that it allows the manipulation of contrast to highlight different tissue types.  The new surgical and pharmacologic options available to treat damaged cartilage and the need to monitor the effects of treatment, have led to the development of various MRI techniques that allow morphologic assessment of cartilage, quantification of its volume and evaluation of its biochemical composition. 
MRI, by virtue of its superior soft-tissue contrast, lack of ionizing radiation and multiplanar capabilities, is superior to more conventional techniques for the evaluation of articular cartilage.  Hence, MRI is the most important imaging modality for the evaluation of traumatic or degenerative cartilaginous lesions in the knee.  It is a powerful non-invasive tool for detecting such lesions and monitoring the effects of pharmacologic and surgical therapy.
| Materials and Methods|| |
A prospective study was carried out on 150 patients in the Department of Radio-diagnosis, Padmashree Dr. D. Y. Patil Medical College, Hospital and Research Center, Pimpri, Pune over a period of 2 years from June 2011 to May 2013. Patients from all age groups including both men and women with pain in the knee joint were included. Diagnosed cases of any tumor in the knee joint or those who had already undergone or selected for knee surgery were excluded. Patients having fracture or dislocations of the knee joint were also excluded.
Detailed clinical history, physical and systemic examination findings were noted in addition to the laboratory investigations. All patients were subjected to radiograph of knee AP and lateral view. MRI was performed with Siemens 1.5 Tesla MAGNETOM Avanto machine. An eight-channel knee coil was used.
MRI examination of the knee was performed in axial, coronal and sagittal planes. T2 weighted fast spin echo (FSE) contrast images were obtained in axial, sagittal and coronal planes. FSE improves visualization of articular cartilage, edema, fluid and contusions. Proton density (PD) FSE images were obtained in axial and sagittal planes. Articular cartilage is best visualized using on PD FSE. T1 weighted images were obtained in coronal and sagittal sequences. Osseous structures are best visualized on T1 weighted images. A T2* gradient echo sagittal sequence improves accuracy of detection of meniscal lesions. Short tau inversion recovery images were obtained in the coronal plane to improve visualization of osseous contusions and muscle trauma [Figure 1] and [Figure 2].
|Figure 1: Sagittal T2 weighted image showing normal trilaminar appearance of articular cartilage|
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|Figure 2: Coronal short tau inversion old female presented with recovery showing various ligaments in knee|
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Each knee was assessed for cartilage defects, subchondral bone marrow lesions, osteophytes, subchondral cysts, meniscal abnormalities, ligamentous abnormalities (including anterior cruciate [ACL], posterior cruciate [PCL], medial collateral [MCL] and lateral collateral [LCL] ligaments), joint effusions, Baker cysts and synovitis. A description of the MRI sequences protocol. Outerbridge articular cartilage defect grading system was used [Table 1]. 
| Results|| |
The study was carried out on 150 patients. Out of which 78 (52%) were females and 72 (48%) were males. Age distribution was as follow: 58 patients (38. 6%) were in the age group of 60-80 years, 51 (34%) in the age group 40-60 years, 29 (19.3%) in the age group 20-40 years and 12 (8%) in the age group of 0-20 years. Majority of patients were in the age group of 60-80 years [Figure 8].
In our study, 60 patients (40%) had no cartilage defects. Out of 90 patients with cartilage defects, 30 patients (20%) had full thickness cartilage defects. Twenty five patients (16.7%) had Grade 1 lesions, 15 patients (10%) had Grade 2 lesions and 20 patients (13.7%) had Grade 3 lesions [Table 2]. Full thickness articular cartilage defects of medial, lateral and patella-femoral compartments were present in 10% (15 patients), 4% (6 patients) and 20 patients (30%) respectively [Figure 4] and [Figure 5].
|Table 2: Grading of articular cartilage lesion in our study according to outerbridge classification|
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|Figure 4: A 68-year-old woman with knee pain. Full thickness tear (black arrow) can be seen at medial tibial articular cartilage with denudation of underlying bone. Signal abnormality seen at lateral tibial condyle as white arrow was given as Grade 1 articular cartilage|
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|Figure 5: 40-year-old man with knee pain. Defect of more than 50% of articular cartilage at medial femoral condyle (Grade 3), which is seen at white arrow Erosion of less than 50% is noted at tibial plateau (Grade 2), which is shown as black arrow|
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Subchondral bone marrow edema was seen beneath 30 patients (20%) who had articular cartilage defects. Most bone marrow lesions were found in patellofemoral compartment [Figure 3].
Meniscal tears, both simple and complex, occurred with greater frequency in the medial compartment compared with the lateral compartment [Table 3]. Notably, 21.1% (32) of all knees had a complex or macerated meniscal tear. Most knees had some degree of meniscal extrusion and the meniscus was extruded ≥5 mm in 17.6% of the knees; this was more common in the medial compartment compared with the lateral compartment.
There were few complete tears of the ACL or LCL and no tears of the PCL or MCL [Table 4].
Synovitis was present in 24.7% (37) of the knees; synovitis was rated as moderate to marked in 6% (9 knees). Joint effusions were detected in 70% (105) of the knees. Large Baker cysts were observed in 6.1% of the knees [Figure 6].
|Figure 6: A 60-year-old woman with knee pain since 6 months. Axial proton density (PD) and Sagittal PD show a Baker cyst in the medial head of gastrocnemius|
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The frequency of osteophytes was congruent with the prevalence of radiographically defined osteoarthritis in this sample. Subchondral cysts were found in approximately one-third of the knees.
| Discussion|| |
The study was carried out on 150 patients with knee pain. MRI, by virtue of its superior soft-tissue contrast, lack of ionizing radiation and multiplanar capabilities, is superior to more conventional techniques for the evaluation of articular cartilage. MRI is also useful for evaluating the integrity of the ligaments, meniscal tears and osteochondral injuries.
Mary Fran Sowers et al. carried out a study in Michigan Hospital on associations of anatomical measures from MRI with radiographically defined knee osteoarthritis score (Lawrens Kellgren Score). Full-thickness cartilage defects of the medial, lateral and patella-femoral compartments were present in 14.5% (105 knees), 4.6% (33 knees) and 26.2% (190 knees), respectively.  In our study, full thickness articular cartilage defects of medial, lateral and patella-femoral compartments were present in 10% (15 patients), 4% (6 patients) and 20 patients (30%) respectively.
In our study, 60 patients (40%) had no cartilage defects, 25 patients (16.7%) had Grade 1 lesions, 15 patients (10%) had Grade 2 lesions, 20 patients (13.3%) had Grade 3 lesions and 30 patients (20%) had Grade 4 lesions. Jungius et al. studied cartilage defects in 336 patients with knee pain. 212 (63%) of 336 surfaces were classified as Grade 0 (normal); 37 (11%) as Grade 1 abnormalities; 30 (9%) as Grade 2 lesions; 25 (7%) as Grade 3 lesions; and 32 (10%) as Grade 4 lesions. 
Kijowski et al. did retrospective study on detection of bone marrow edema who had articular cartilage defects. Subchondral bone marrow edema was seen beneath 105 (19%) of 554 articular cartilage defects.  In our study, marrow edema was found in 30 patients (20%) who had articular cartilage defects.
Hill et al. did study on cruciate ligament integrity in patients with knee pain using MRI. The study was performed in 360 patients. Complete ACL rupture was 22.8% and PCL rupture in 0.6%.  In our study, complete ACL ruptures was found in 7 patients (4.6%). The difference in the results could be due to the difference in patient selection criteria in both studies.
In our study, prevalence of meniscal tear ranged from 15% among women 40-60 years of age to 45% among men age 60-80 years of age. Englund et al. did study on menisci findings in patients with knee pain in 2008. The prevalence of a meniscal tear as detected on MRI ranged from 19% among women 50-59 years of age to 56% among men 70-90 years of age. 
Kolman et al. did correlation of joint fluid and internal derangement on knee MRI. Thirty-six patients out of total 105 patients (31%) showed joint fluid with anteroposterior measurement of 10 mm or less in the lateral aspect of the suprapatellar pouch.  In our study, 60 patients (40%) showed anteroposterior measurement of 10 mm or more which was considered pathological.
| Conclusion|| |
MRI enables a non-invasive, three-dimensional assessment of the entire joint, simultaneously allowing the direct visualization of articular cartilage. Although radiography, the current gold standard for the assessment of osteoarthritis (OA), has had recent significant technical advances, radiographic methods have significant limitations when used to measure disease progression. MRI allows accurate and reliable assessment of articular cartilage, which is sensitive to change, providing the opportunity to better examine and understand preclinical and very subtle early abnormalities in articular cartilage, prior to the onset of radiographic disease.
MRI enables quantitative (cartilage volume and thickness) and semi-quantitative assessment of articular cartilage morphology and quantitative assessment of cartilage matrix composition. Cartilage volume and defects have demonstrated adequate validity, accuracy, reliability and sensitivity to change. They are correlated to radiographic changes and clinical outcomes such as pain and joint replacement [Figure 7].
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8]
[Table 1], [Table 2], [Table 3], [Table 4]