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Imaging the knee

Nuffield Orthopaedic Centre and Oxford Radcliffe Hospital, Oxford, UK

View larger version (34K): [in a new window]   Figure 1. Basic types of meniscal tears: (a) vertical circumferential; (b) bucket handle tear; (c) vertical radial; (d) horizontal oblique.

View larger version (101K): [in a new window]   Figure 2. Bucket handle tear. (a) Double posterior cruciate ligament (PCL) sign. The low signal meniscal fragment is seen lying in the intercondylar region (arrow) giving a double PCL appearance. (b) The peripheral portion of the meniscus is attenuated (arrow).

View larger version (166K): [in a new window]   Figure 3. Pseudohypertrophy of the anterior third of the lateral meniscus. The posterior third of the meniscus has been displaced anteriorly giving the impression of a large anterior third of the meniscus (arrow). Note attenuated posterior third.

View larger version (101K): [in a new window]   Figure 4. Flap tear. The displaced meniscal fragment is seen lying in the posterior medial joint space on (a) sagittal and (b) coronal scans (arrows).

View larger version (141K): [in a new window]   Figure 5. Displaced meniscal tear. A fragment of the torn mid portion of the meniscus is seen to be displaced in the medial gutter (arrow).

View larger version (137K): [in a new window]   Figure 6. Vertical circumferential tear of the posterior third of the medial meniscus with minor displacement of the free edge (arrow).

View larger version (157K): [in a new window]   Figure 7. Meniscocapsular separation. There is fluid seen behind the meniscus. The meniscus is displaced anteriorly leaving a "bare area" of tibia posteriorly (arrow).

View larger version (124K): [in a new window]   Figure 8. Radial tear. The tear is seen as a discontinuity of the normal "bow tie" configuration of the mid portion of the meniscus (arrow).

View larger version (126K): [in a new window]   Figure 9. Radial type tear of the posterior third of the medial meniscus close to its tibial attachment. (a) Coronal view shows a tear of the meniscus near the tibial attachment (arrow). (b) Sagittal scan along the plane of the tear shows a ghost-like appearance of the meniscus (arrow). (c) Coronal image through the middle of the knee shows medial displacement of the mid portion of the meniscus (arrow).

View larger version (75K): [in a new window]   Figure 10. Discoid meniscus. (a) Coronal scan through the middle of the knee shows that the lateral meniscus extends across the entire joint compartment (arrow). (b) On sagittal scan the bow tie appearance of the meniscus persists into the centre of the joint compartment.

View larger version (104K): [in a new window]   Figure 11. Acute anterior cruciate ligament (ACL) tear. (a) Well defined straight fibres of the normal ACL (arrows). (b) In the acute ACL tear the normal ligament is replaced by a high signal heterogeneous mass (arrow).

View larger version (90K): [in a new window]   Figure 12. Acute anterior cruciate ligament (ACL) tear. (a) On the sagittal scan a curved ligament can be seen lying in the expected position of a normal ACL (arrow). (b) Coronal image showing avulsion of the ligament at its femoral attachment (arrow).

View larger version (92K): [in a new window]   Figure 13. Typical pattern of bony injury associated with anterior cruciate ligament tear. (a) Gradient echo T2 weighted sagittal image showing evidence of trabecular trauma at the posterior portion of the lateral tibial plateau (arrow) and a small impaction fracture of the lateral femoral condyle (open arrow). (b) Short tau inversion recovery coronal image showing the small impaction fracture of the lateral femoral condyle (arrow) with subchondral oedema. Note associated articular cartilage defect.

View larger version (81K): [in a new window]   Figure 14. (a) Typical vertical circumferential tear of the posterior third of the lateral meniscus associated with AC tear (arrow). (b) Normal attachment of a prominent meniscofemoral ligament (arrow) mimicking a tear.

View larger version (174K): [in a new window]   Figure 15. Acute posterior cruciate ligament tear. There is diffuse increased signal and widening of the ligament with focal disruption (arrow).

View larger version (172K): [in a new window]   Figure 16. Acute medial collateral ligament tear. The proximal portion of the ligament is widened and contains increased signal (arrows). There is associated soft tissue haemorrhage/oedema medial to the ligament.

View larger version (168K): [in a new window]   Figure 17. Tear of the deep fibres of the medial collateral ligament (MCL). There is widening and increased signal deep to the superficial fibres of the MCL (arrow). There is some minor associated oedema in the adjacent portion of the femoral condyle.

View larger version (102K): [in a new window]   Figure 18. Isolated tear of the lateral collateral ligament at the fibular insertion (arrow).

View larger version (91K): [in a new window]   Figure 19. Recent patellar dislocation. (a) Sagittal short tau inversion recovery image shows oedema adjacent the lateral aspect of the lateral femoral condyle (arrow). (b) Axial image showing a large defect in the retropatellar cartilage (arrow). An articular cartilage fragment is embedded in the synovium of the lateral recess (open arrow). There is widening of the medial retinaculum (*).

View larger version (98K): [in a new window]   Figure 20. Posterior capsule tear following hyperextension injury. (a) Sagittal image shows a tear of the posterior capsule (arrow). (b) Coronal short tau inversion recovery image shows fluid surrounding the popliteal vessels. (c) There is an associated vertical tear of the anterior third of the lateral meniscus (arrow).

View larger version (95K): [in a new window]   Figure 21. Posterolateral corner injury. (a) Short tau inversion recovery (STIR) coronal scan showing oedema in the tip of the fibula (arrow) due to avulsion injury by the "arcuate complex". The popliteofibular ligament is well demonstrated (open arrow). (b) STIR coronal scan in a different case with acute rupture anterior cruciate ligament. There is high signal medial to the collateral ligament in keeping with tear of the popliteofibular ligament.

View larger version (173K): [in a new window]   Figure 22. Typical degenerative horizontal oblique type tear of the posterior third of the medial meniscus extending to the inferior articular surface (arrow).

View larger version (125K): [in a new window]   Figure 23. Chronic anterior cruciate ligament tear. The ligament is lying on the floor of the intercondylar region (arrows).

View larger version (104K): [in a new window]   Figure 24. Iliotibial band friction syndrome. There is some increased signal (arrow) related to the deep surface of the iliotibial band.

View larger version (68K): [in a new window]   Figure 25. Articular cartilage defects. (a) Sagittal volume acquisition gradient echo (DESS) sequence showing small defect in the articular cartilage of the medial femoral condyle. (b) Axial T2 weighted fast spin echo image showing full thickness defect involving the medial facet of the patella (arrow).

View larger version (186K): [in a new window]   Figure 26. Occult tibial plateau fracture. Sagittal proton density fat suppression image clearly shows fracture line (arrows).

View larger version (91K): [in a new window]   Figure 27. Insufficiency fracture secondary to rheumatoid associated osteoporosis. (a) Coronal short tau inversion recovery image showing extensive oedema in the medial tibial plateau. Note marginal erosion (arrow). (b) More anterior slice shows the typical low signal line surrounded by oedema (arrow).

View larger version (142K): [in a new window]   Figure 28. Spontaneous osteonecrosis of the knee. Coronal short tau inversion recovery image showing a focal low signal subchondral lesion in the medial femoral condyle (arrow) surrounded by extensive oedema. There is some flattening of the articular surface.

View larger version (165K): [in a new window]   Figure 29. Osteochondritis dissecans of the medial femoral condyle. Coronal short tau inversion recovery image. There is high signal line surrounding the low signal necrotic fragment (arrow) indicating instability.

View larger version (114K): [in a new window]   Figure 30. Osteonecrosis. (a) Coronal T1 weighted and (b) short tau inversion recovery images showing the typical geographic lesions containing fat signal (arrows). The femoral infarct has breached the articular surface.

View larger version (188K): [in a new window]   Figure 31. Pigmented villonodular synovitis. Gradient echo T2 weighted image showing extensive synovial hypertrophy returning low signal intensity (arrows).

View larger version (73K): [in a new window]   Figure 32. Lipoma arborescens. (a) T1 weighted and (b) short tau inversion recovery axial scans through the suprapatellar pouch showing fatty synovial villous mass projecting into the joint.

View larger version (76K): [in a new window]   Figure 33. Synovial sarcoma. (a) Plain radiograph shows a calcified soft tissue mass on the lateral aspect of the knee. (b) T2 weighted axial image shows a mass containing extensive low signal representing the tumour calcification (arrows).

View larger version (76K): [in a new window]   Figure 34. Synovial osteochonromatosis. (a) Plain film showing multiple ossified foci behind the knee. (b) On ultrasound the popliteal cyst is filled with solid tumour containing calcific foci.

View larger version (158K): [in a new window]   Figure 35. Focal pigmented villonodular synovitis. T2 weighted image showing focal lesion in Hoffa's fat pad (arrow). There are scattered low signal foci representing fibrosis and haemosiderin deposits.

View larger version (137K): [in a new window]   Figure 36. Semimembranosus bursitis. Axial short tau inversion recovery image showing distended bursa at the pes anserinus (arrow).

View larger version (104K): [in a new window]   Figure 37. Ultrasound showing typical configuration of a popliteal cyst with a neck communicating with the joint between the medial head of gastrocnemius (MG) and semimembranosus (SM).

View larger version (111K): [in a new window]   Figure 38. Meniscal cyst. Cornonal T2 weighted image showing a meniscal cyst (arrow) communicating with a horizontal tear of the mid portion of the lateral meniscus.

View larger version (106K): [in a new window]   Figure 39. Ganglion arising from the patellar tendon. Ultrasound image showing a typical anechoic lesion (arrow). The lesion is connected to the patellar tendon via a stalk (open arrow).

View larger version (88K): [in a new window]   Figure 40. Anterior cruciate ligament (ACL) ganglion. (a) Sagittal gradient echo T2 weighted image showing a ganglion intimately related to the ACL (arrow). (b) Short tau inversion recovery coronal image showing some of the ACL fibres being separated by the cyst (arrow).

View larger version (103K): [in a new window]   Figure 41. Ganglion of the common peroneal nerve in patient with foot drop. (a) Ultrasound shows widened hypoechoic mass (arrow) along the course of the nerve at the fibula neck (F). (b) The lesion is seen as high signal on short tau inversion recovery coronal MRI (arrow). (c) Axial T2 image show high signal in anterior compartment indicating denervation of tibialis anterior.

View larger version (129K): [in a new window]   Figure 42. Patellar tendinosis. (a) T2 weighted sagittal image showing high signal lesion in the deep portion of the tendon (arrow). (b) Sagittal ultrasound of the proximal patellar tendon showing a widened tendon with reduction in reflectivity (arrows). There is marked increased vascularity seen in the region (P=patella).

View larger version (77K): [in a new window]   Figure 43. Osgood Schlatter's disease. Sagittal ultrasound image showing fragmentation of the tibial tubercle (arrow) and widening of the distal patellar tendon (open arrow).

View larger version (146K): [in a new window]   Figure 44. Chondromalacia patellae. T2 weighted axial image. Minor retropatellar articular cartilage defects are seen.

View larger version (124K): [in a new window]   Figure 45. Reconstructed axial MRI through the proximal part of the trochlear groove. The articular surface has an abnormaly flat configuration.

View larger version (66K): [in a new window]   Figure 46. Patellar subluxation. Two images from a dynamic tracking study. (a) Normal position of the patellae with the knees flexed at 40°. (b) With the knees in the extended position there is bilateral subluxation of both patellae.

View larger version (127K): [in a new window]   Figure 47. Anterior cruciate ligament graft. T2 weighted image showing (a) intact ligament (b) acute tear.

View larger version (115K): [in a new window]   Figure 48. Recurrent meniscal tear. (a) Proton density with fat suppression shows high signal lesion within the meniscal remnant. This could represent a simple tear (b) T1 weighted fat suppression MR following intraarticular injection of dilute solution of gadolinium showing recurrent tear (arrow).