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=== '''Introduction''' ===
=== '''Introduction''' ===
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[[Image:Knee
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|thumb|right|251x251px|Knee Anatomy]]
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[[Image:Knee
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|thumb|right|251x251px|Knee Anatomy]]
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Reprinted from www.drwaltlowe.com
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While a thorough history and physical examination are the most important instruments in evaluating knee joint pain, musculoskeletal imaging is an important adjunct.<ref name="Berry">Berry DJ, Stein mann SP. Adult Reconstruction. Philadelphia, PA: Lipinncott Williams Wilkins, a Walters Kluwer business; 2007: 130-139.</ref> Imaging typically begins with a standard set of plain radiographs, with special radiographic views and more elaborate modalities used if indicated. '''<ref name="Berry" />'''
While a thorough history and physical examination are the most important instruments in evaluating knee joint pain, musculoskeletal imaging is an important adjunct.<ref name="Berry">Berry DJ, Stein mann SP. Adult Reconstruction. Philadelphia, PA: Lipinncott Williams Wilkins, a Walters Kluwer business; 2007: 130-139.</ref> Imaging typically begins with a standard set of plain radiographs, with special radiographic views and more elaborate modalities used if indicated. '''<ref name="Berry" />'''
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[[Image:Radiograph for knee OA.jpg]]
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[[Image:Radiograph for knee OA.jpg
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Figure 2: Radiograph for knee OA. Reprinted from http://stemcelldoc.wordpress.com/2011/11/16/knee-osteoarthritis-grading-limitations-of-x-rays/<br>
Figure 2: Radiograph for knee OA. Reprinted from http://stemcelldoc.wordpress.com/2011/11/16/knee-osteoarthritis-grading-limitations-of-x-rays/<br>
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[[Image:MRI for knee OA.jpg|240x239px]]
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Figure 3: MRI for knee arthritis. Reprinted from http://www.lurj.org/article.php/vol2n1/arthritis.xml
Figure 3: MRI for knee arthritis. Reprinted from http://www.lurj.org/article.php/vol2n1/arthritis.xml
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• Radiographs are performed with the knee in 20 degrees of flexion with comparisons made between the amount of gapping in the injured and uninjured knee
• Radiographs are performed with the knee in 20 degrees of flexion with comparisons made between the amount of gapping in the injured and uninjured knee
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[[Image:Varus Stress Radiograph of LCL tear.jpg|181x181px]]<br>Figure 4: Varus stress radiograph of grade III LCL tear. Reprinted from The Journal of Bone and Joint Surgery. http://jbjs.org/article.aspx?Volume=90&page=2069
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[[Image:Varus Stress Radiograph of LCL tear.jpg
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|181x181px]]<br>Figure 4: Varus stress radiograph of grade III LCL tear. Reprinted from The Journal of Bone and Joint Surgery. http://jbjs.org/article.aspx?Volume=90&page=2069
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• Use of a coronal plane MRI (fast-spin echo T 2 weighted image)<br>• Look for intermediate signal (consistent with edema), slight thickening and possible retraction of the ligament with possible separation from underlying cortices
• Use of a coronal plane MRI (fast-spin echo T 2 weighted image)<br>• Look for intermediate signal (consistent with edema), slight thickening and possible retraction of the ligament with possible separation from underlying cortices
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[[Image:MRI for MCL tear.jpg]]<br>Figure 5: Grade III medial collateral ligament tear on a coronal fast spin-echo T2-weighted image demonstrates a disrupted ligament that is thickened and retracted, with surrounding edema (black arrow). Reprinted from Medscape Reference. http://emedicine.medscape.com/article/401472-overview
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[[Image:MRI for MCL tear.jpg
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]]<br>Figure 5: Grade III medial collateral ligament tear on a coronal fast spin-echo T2-weighted image demonstrates a disrupted ligament that is thickened and retracted, with surrounding edema (black arrow). Reprinted from Medscape Reference. http://emedicine.medscape.com/article/401472-overview
=== '''Anterior Cruciate Ligament Tears (ACL)''' ===
=== '''Anterior Cruciate Ligament Tears (ACL)''' ===
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• The cruciate ligaments course obliquely through the intercondylar notch and need to be followed on consecutive slices.<br>• These structures are usually not seen in entirety on one slice, and caution should be exercised in diagnosing a tear on a single slice. <br>• Look for discontinuity of the ACL in the coronal and sagittal planes<br>• There are often secondary signs of an anterior cruciate ligament (ACL) injury, such as a joint effusion and bone contusions
• The cruciate ligaments course obliquely through the intercondylar notch and need to be followed on consecutive slices.<br>• These structures are usually not seen in entirety on one slice, and caution should be exercised in diagnosing a tear on a single slice. <br>• Look for discontinuity of the ACL in the coronal and sagittal planes<br>• There are often secondary signs of an anterior cruciate ligament (ACL) injury, such as a joint effusion and bone contusions
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[[Image:MRI for ACL tear.jpg|185x121px]]
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Figure 6: Sagittal MRI demonstrating ACL rupture. Reprinted from Sports-Med Forum. http://www.sportsmed-forum.com/index-1/st_pag_patients-home/sm_pag_case-studies-2/sm_pag_case-knee/sm_pag_acl.htm
Figure 6: Sagittal MRI demonstrating ACL rupture. Reprinted from Sports-Med Forum. http://www.sportsmed-forum.com/index-1/st_pag_patients-home/sm_pag_case-studies-2/sm_pag_case-knee/sm_pag_acl.htm
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• Look for areas of abnormal morphology<br>• Abnormally increased T1 and T2 signals (often linearly orient¬ed) intersect the edges of the meniscus along the articular surface
• Look for areas of abnormal morphology<br>• Abnormally increased T1 and T2 signals (often linearly orient¬ed) intersect the edges of the meniscus along the articular surface
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<br> [[Image:MRI for meniscus tear.jpg|159x172px]]
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<br> [[Image:MRI for meniscus tear.jpg
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Figure 7: Coronal T2-weighted fat-saturated fast spin-echo image showing fraying and mild blunting of free edge of body of medial meniscus (large arrow) and horizontal tear of lateral meniscus (small arrow). Reprinted from American Journal of Roentgenology. http://www.ajronline.org/content/187/1/221/F3.expansion.html
Figure 7: Coronal T2-weighted fat-saturated fast spin-echo image showing fraying and mild blunting of free edge of body of medial meniscus (large arrow) and horizontal tear of lateral meniscus (small arrow). Reprinted from American Journal of Roentgenology. http://www.ajronline.org/content/187/1/221/F3.expansion.html
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=== '''Osteochondral Defects''' ===
=== '''Osteochondral Defects''' ===
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Osteochondral defects (focal areas of articular damage with cartilage damage and injury of the adjacent subchondral bone) are best viewed on MRI.
MRI is the test of choice due to its ability to detect the presence of osteochondral fragmentation, which is essential for clinical management. MRI demonstrates high sensitivity (92%) and specificity (90%) in the detection of separation of the osteochondral fragment.
Both x-rays and CT are able to detect displaced defects with ease; however they are insensitive in grading lower stage lesions, and are inadequate in predicting stability.<ref name="Weerakkoddy">Weerakkody Y, Gaillard F. Osteochondral Defect. Radiopaedia Web site. http://radiopaedia.org/articles/osteochondral-defect. Accessed June 25, 2012.</ref>
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Osteochondral defects (focal areas of articular damage with cartilage damage and injury of the adjacent subchondral bone) are best viewed on MRI.MRI is the test of choice due to its ability to detect the presence of osteochondral fragmentation, which is essential for clinical management. MRI demonstrates high sensitivity (92%) and specificity (90%) in the detection of separation of the osteochondral fragment.Both x-rays and CT are able to detect displaced defects with ease; however they are insensitive in grading lower stage lesions, and are inadequate in predicting stability.<ref name="Weerakkoddy">Weerakkody Y, Gaillard F. Osteochondral Defect. Radiopaedia Web site. http://radiopaedia.org/articles/osteochondral-defect. Accessed June 25, 2012.</ref>
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[[Image:MRI for osteochondral defect.jpg|319x149px]]
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Figure 8: (A) Osteochondral defect. This coronal T1 sequence shows an area of abnormally low T1 signal in the lateral weight-bearing portion of the medial femoral condyle (arrow), characteristic of osteochondral defect. (B) Osteochondral defect. This sagittal T2 sequence with fat saturation shows subchondral irregularity and heterogeneously low T2 signal with adjacent bone marrow edema in the medial femoral condyle (arrow) characteristic of osteochondral defect. Reprinted from Tall et al.<ref name="Tall" />
Figure 8: (A) Osteochondral defect. This coronal T1 sequence shows an area of abnormally low T1 signal in the lateral weight-bearing portion of the medial femoral condyle (arrow), characteristic of osteochondral defect. (B) Osteochondral defect. This sagittal T2 sequence with fat saturation shows subchondral irregularity and heterogeneously low T2 signal with adjacent bone marrow edema in the medial femoral condyle (arrow) characteristic of osteochondral defect. Reprinted from Tall et al.<ref name="Tall" />
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• In a lateral radiograph look for patella alta and/or patellar osteochondral fracture<br>• In a axilla radiograph look for increased sulcus angle – normal sulcus angle is 137-141 <br>• In a merchant technique look for trochlea dysplasia and an increased congruence angle (compared to the reference sulcus angle from the axilla view)<br>• Normal congruence angle is defined as < - 16 degrees (negative values indicate medial positioning)
• In a lateral radiograph look for patella alta and/or patellar osteochondral fracture<br>• In a axilla radiograph look for increased sulcus angle – normal sulcus angle is 137-141 <br>• In a merchant technique look for trochlea dysplasia and an increased congruence angle (compared to the reference sulcus angle from the axilla view)<br>• Normal congruence angle is defined as < - 16 degrees (negative values indicate medial positioning)
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[[Image:Congruence angle for patellar positioning.jpg]]<br>Figure 9: How to calculate congruence angle through the bisection of the sulcus angle. Reprinted from Wheeless CR.<ref name="Wheeless" /> <br>
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[[Image:Congruence angle for patellar positioning.jpg
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]]<br>Figure 9: How to calculate congruence angle through the bisection of the sulcus angle. Reprinted from Wheeless CR.<ref name="Wheeless" /> <br>
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[[Image:Radiograph for patellar subluxation.jpg|216x155px]]
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Figure 10: Merchant view radiograph of a lateral patellar subluxation, demonstrating a + 23 degree congruence angle. Reprinted from The Journal of Bone and Joint Surgery. http://jbjs.org/article.aspx?Volume=79&page=1759
Figure 10: Merchant view radiograph of a lateral patellar subluxation, demonstrating a + 23 degree congruence angle. Reprinted from The Journal of Bone and Joint Surgery. http://jbjs.org/article.aspx?Volume=79&page=1759
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=== Videos ===
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{| width="100%" cellspacing="1" cellpadding="1" class="FCK__ShowTableBorders"
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| {{#ev:youtube|CPoRHy_ET4U|300}} <ref>Chris Centeno. How to Read Knee MRI. Available from: http://www.youtube.com/watch?v=CPoRHy_ET4U [last accessed 12/09/14]</ref>
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| {{#ev:youtube|OqXgq7C_CYk|300}}<ref>TeachMeAnatomy. Interpreting X-Rays of the Knee Joint. Available from: http://www.youtube.com/watch?v=OqXgq7C_CYk [last accessed 12/09/14]</ref>
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=== '''References''' ===
=== '''References''' ===
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[[Diagnostic Imaging for Physical Therapists]]
[[Diagnostic Imaging for Physical Therapists]]
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[[Category:Assessment]]
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[[Category:Assessment
]][[Category:Articles]][[Category:Videos]][[Category:Anatomy]][[Category:Knee
]]