X ray knee joint

IMAGING features in knee

1. X-ray Knee joint Dr. Athul.D JR MDRD

2. Anatomy of knee joint is a synovial hinge  joint  formed between three  bones : 

3. Ligaments

4. Views of knee joint AP view Lateral view Intercondylar view Skyline view/sunrise view

5. AP VIEW Patient Position: Supine or upright. Internally rotate the leg slightly (5°) so that the knee is in a true AP position . Kvp : 60 5 degree cephalad tube tilt CR:1 cm inferior to the patellar apex because the joint space lie 1cm inferior .

6. In AP View The medial and lateral margins of the femoral condyles and opposing tibial condyles should be in vertical alignment. The patella should lie centrally over the distal femur. The fibula head is overlapping the tibial condyle. Normal femorotibial joint space - 4 to 6 mm

7. X-ray anatomy 1. Femoral shaft. 2. Medial epicondyle. 3. Lateral epicondyle. 4. Medial condyle. 5. Lateral condyle. 6. Intercondylar notch. 7. Intercondylar eminences (tibial spines). 8. Medial condyle of the tibia. 9. Lateral condyle of the tibia. 10. Head of the fibula. 11. Neck of the fibula. 12. Adductor tubercle. 13. Medial joint space. 14. Lateral joint space. 15. Tibial shaft. 16. Patella.

8. Specialised projections: Weight bearing view Rosenburg’s view Tibial plateau view Varus-valgus stress views Internal-external oblique views AP tibia-fibula view

9. Weight bearing view Upright AP view Single knee-full weight on the affected side. Upright views frequently identify joint space narrowing, femorotibial subluxation and/ or varus –valgus instability when non-weight-bearing views appear normal.

10. Rosenburg view Upright PA with 10 degree caudal tube tilt Knees flexed to 45 degree. Intercondylar notch appears in this view to show degenerative sclerosis, cysts, and osteochondral defects ( including osteochondritis dissecans).

11. Tibial plateau view Angling the tube 15 degree cephalad provides tangential view of tibial plateau. Useful in trauma for depression of the articular surface and fractures

12. Varus valgus stress views Femur stabilised by third person Studies taken at varus and valgus Width of joint space (5-7mm)and femorotibial shift(<1mm) is assessed. As a sign of collateral ligament stability.

13. Internal Oblique view Leg is rotated internally by 45 degree 5 degree cephalad tube tilt Tibiofibular joint well visualised

14. The medial oblique shows the tibiofibular joint to advantage and avulsion fractures of the head of the fibula and lateral tibial condyle ( Segond’s fracture )

15. External oblique view Leg is rotated externally by 45 degree 5 degree cephalad tube tilt Femoral condylar surface,tibial plateau,tibial spines better visualised .

16. Ap tibia fibula views Ankle dorsiflexed With ankle malleoli equidistant from the film Includes both knee and ankle in the film

17. REVIEW OF AP VIEW Projection Advantage Weight bearing view To identify joint space narrowing, femorotibial subluxation & varus –valgus instability Rosenburg’s view to show degenerative sclerosis, cysts, and osteochondral defects Tibial plateau view useful in trauma to investigate depression of the articular surface and fractures. Varus-valgus stress views For assessing collateral ligament stability. Internal-external oblique views shows the tibiofibular joint and avulsion fractures of the head of the fibula and lateral tibial condyle AP tibia-fibula view preferable for including both the knee and ankle in the field.

18. Lateral view Patient Position : Lateral recumbent. Flex the lower leg about 45° to traction the patella in place. 5 degree cephalad tube tilt(true lateral) CR : 1 cm distal to the medial epicondyle

19. Anatomy in lateral view 1. Anterior intercondylar area. 2. Posterior intercondylar area. 3. Tibial tuberosity. 4. Tibial shaft. 5. Head of fibula. 6. Fabella gastrocnemius tendon; 7. Patella. 8. Lateral condyle. 9. Femoral shaft. 10. Superior pole, patella. 11. Inferior pole, patella. 12. Infrapatellar fat (Hoffa’s fat-pad). 13. Suprapatellar fat, femoral surface

20. Anterior and posterior cortex of patella are prominent producing trilaminar appearance

21. Insall salvatti index Ratio of Patellar tendon length/patella length Range lies between 0.7-1.5 patella baja: <0.8 (perhaps <0.74) patella alta: >1.2 (perhaps >1.5)

22. Patella baja Low lying patella Result of quadriceps tendon rupture B  for "below" ( b aja )  , Patella alta High riding patella Due to patellar tendon rupture/ chondromalacia patellae   A  for "above" ( a lta )

23. Modified Insall-Salvati ratio Also applied on a lateral 30 degree flexed knee radiograph, A: distance from the inferior margin of the patellar articular surface the patellar tendon insertion B: length of the patellar articular surface   Modified Insall-Salvati ratio = A/B

24. The modified Insall-Salvati ratio is considered normal around 1.25, abnormal when >2 which is considered diagnostic of patella alta.

25. Ludloffs Lucency Distinct radiolucency over the superimposed condyles- ludloff’s lucency

26. Blumensaat’s line Line through the roof of the intercondylar notch indicating the relative position of the patella as normally this line intersects the lower pole of the patella suggesting ACL injury as the normal ACL Blumensaat angle is ≤15° describing the course of an ACL graft identifying the location of the lateral femoral condyle sulcus, which should be within 10mm of the line

27. Parsons Knob Third intercondylar eminence Small bony bump seen anterior to tibial spine. Insertion point of anterior cruciate ligament. Enlarges with osteoarthritis DDX – intra articular body - Intra articular osteochondroma

28. Hoffas Fat pad infrapatellar fat ( Hoffa’s fatpad ), which occupies the soft tissue below the patella anteriorly, is roughly triangular in shape, is radiolucent

29. Due to the imbalance of forces between vastus medialis and lateralis,impingement of superolateral aspect of fatpad occurs. Anterior knee pain

30. Suprapatellar pouch Thread like shadow Bounded anteriorly and posteriorly by fat pad Thickening of the pouch is the sensitive sign of joint effusion. 10mm pouch thickness implies 10 ml of joint fluid.

31. Special views in lateral projection Cross table lateral view This cross table lateral view of the knee is the traditional way of viewing a lipohemarthrosis of the knee. Here, the black arrow indicates blood with fat (white arrow) layering superiorly. knee is fully extended. An exposure with the mAs reduced by at least 50% and a horizontal beam may demonstrate a fat–blood interface effusion (FBI sign) in the suprapatellar pouch as a marker of lipohemarthrosis

32. Tibial tuberosity view Slight internal rotation of the tibia by 5° with lowered kVp and mAs will assist in demonstrating the anatomic details of the distal patellar tendon, infrapatellar fat, tendo -osseous junction, and surface of the tibial tuberosity

33. Weight bearing view The patella is stabilized by use of a support device and the knee is flexed to 15° in full weight bearing; a horizontal beam is used. Anterior translation of the tibia by > 5 mm is a sign of a deficient anterior cruciate ligament.

34. Quadriceps contraction view: In cross-table lateral with a horizontal beam. A 30° knee bolster is placed in the popliteal fossa, a 15-lb weight suspended from the ankle, and the patient is instructed to fully extend the knee Anterior tibial displacement of > 4 mm is a sign of anterior cruciate ligament rupture.

35. Tunnel view ( notch view, intercondylar fossa view) Part Position: ( a ) Prone The knee is flexed approximately 45°, Kneeling ( Holmblad’s view) in kneeling position and then lean forward so that the shaft of the femur will form a 25° angle with the CR CR: ( a ) Prone: the CR is angled 25° caudad and enters the knee joint at the popliteal depression. Center film to the CR. ( b ) Kneeling ( Holmblad’s view): no tube tilt is used and the CR passes through the knee joint. Center film to the CR.

36. Normal anatomy 1. Femoral shaft. 2. Adductor tubercle. 3. Medial condyle. 4. Lateral condyle. 5. Medial epicondyle. 6. Lateral epicondyle. 7. Popliteal groove. 8. Intercondylar notch. 9. Intercondylar eminences (tibial spines). 10. Medial condyle, tibia. 11. Lateral condyle, tibia. 12. Styloid process, fibula. 13. Neck of fibula. 14. Tibial shaft. 15. Patella.

37. uses Detection of loose bodies (joint mice) Osteochondritis Dissecans

38. Tangential (Skyline, Sunrise) Projection Tube Tilt: 10° cephalad. Patient Position: Prone . The knee is fully flexed. If the patient is unable to fully flex the knee, angle the CR cephalad sot hat a 45° angle exists between the lower leg and the CR. CR: Set the CR between the patella& the femoral condyles. Center film to the CR

39. 1. Odd facet of the patella. 2. Medial facet of the patella. 3. Lateral facet of the patella. 4. External cortical surface of the patella. 5. Patella. 6. Head of the fibula. 7. Tibiofibular articulation. 8. Patellofemoral articulation. 9. Medial condyle. 10. Lateral condyle. 11. Groove for the popliteus tendon. 12. Intercondylar (trochlear) notch. 13. Medial epicondyle. 14. Lateral epicondyle. 15. Adductor tubercle.

40. uses This view is particularly useful for assessing the patella position (subluxation, dislocation), patellofemoral joint pain (chondromalacia, arthritis), retropatellar surface (fracture), and depth of the trochlear groove (dysplasia).

41. Review Projection Advantage Quadriceps contraction view ACL pathology Weight-bearing view: Defects of ACL Tibial tuberosity view patellar tendon, infrapatellar fat & tibial tuberosity Cross-table lateral Lipo-hemarthrosis Intercondylar (Tunnel) view intercondylar notch, loose bodies & osteochondritis Tangential view patella position, patellofemoral joint pain retropatellar surface (fracture), & depth of the trochlear groove (dysplasia)

42. AP Knee, Fracture of the Tibial Plateau Vertical fractures are visible through the medial ( arrowheads ) and lateral tibial plateau ( arrow ). Note the offset of the lateral femoral and tibial condyles owing to fragment displacement.

43. Schatzker classification

44. AP Knee, Degenerative Joint Disease. The medial femorotibial joint space is decreased, with osteophytes and sclerosis of the femoral and tibial condylar surfaces

45. AP Knee, Osteochondroma of the Femur. A cortical exostosis projects off of the distal metaphysis of the femur. Note its calcified cartilaginous cap

46. Lateral view pathologies Suprapatellar Joint Effusion . There is a large fluid effusion in the suprapatellar pouch ( arrows ). Note the preservation of the fat anterior to the femur, which borders the posterior border of the pouch.

47. Paget’s Disease of the Patella and Tibia. The patella and tibia are both increased in density, have thickened cortices, and are enlarged. Observe the transverse fracture of the patella.

48. Degenerative Joint Disease of the Patellofemoral Joint. The patellofemoral joint space is decreased in thickness so that there is almost bone–bone contact between the patella and the femur. There has been a mechanical erosion of the anterior femoral cortex owing to chronic patella impingement ( arrow ).

49. Intercondylar (Tunnel), Knee, Osteochondritis Dissecans single loose body is visible within the intercondylar notch ( arrowhead ). It has originated from the medial condyle, where the defect can be seen ( arrow ).

50. Intercondylar (Tunnel), Knee, Chondroblastoma. well-defined radiolucent lesion is present within the medial femoral condyle ( arrows ). This lesion Seen clearly on the intercondylar view, because the femoral surface is less tangential to the incident beam

51. Patellar fractures M.C -Transverse

52. Tangential, Patella, Dislocation. The patella ( P ) has dislocated laterally relative to the femur ( F ). There is a small fracture fragment adjacent to the lateral femoral condyle ( arrows ).

53. Tangential, Patella, Osteochondritis Dissecans A separating bone fragment is visible from the retropatellar surface involving the majority of the lateral facet and a small part of the medial facet ( arrow ).

54. Supracondylar fracture

55. Segond fracture small fragment of bone avulsed from the lateral aspect of the tibia

56. Sinding-Larsen-Johansson disease Lateral radiograph of the right knee shows fragmentation of the lower pole of the patella and significant soft-tissue swelling associated with calcifications and ossifications of the patellar ligament —findings characteristic of Sinding-Larsen-Johansson disease

57. Osgood-Schlatter disease. fragmentation of the tibial tuberosity (arrows) in association with soft-tissue swelling (open arrow)—characteristic findings in Osgood-Schlatter disease.

58. Chondroblastoma radiolucent lesion located eccentrically in the proximal epiphysis of the tibia , with sharply defined borders and a thin, sclerotic margin (arrows).

59. Osteosarcoma The sunburst or perpendicular type of periosteal reaction on the AP radiograph of the distal femur. Codman triangle (arrow) is also shown

60. Parosteal osteosarcoma. This tumor has a predilection for the posterior aspect of the distal femur.

61. Periosteal chondrosarcoma. a parosteal calcified mass at the medial cortex of distal femur, exhibiting chondroid calcifications.

62. Non ossifying fibroma A sclerotic border or narrow zone of transition from normal to abnormal bone typifies a benign lesion, as in this example of nonossifying fibroma (arrows).

63. Benign fibrous Histiocytoma a lobulated radiolucent lesion with a well-defined sclerotic border, located eccentrically in the proximal tibia.

64. Olliers disease exhibited in extensive involvement of multiple bones and ring-like calcifications in tongues of cartilage

65. Hereditary multiple exostoses. An anteroposterior radiograph of both knees of a 17-year-old boy shows numerous sessile and pedunculated osteochondromas

66. Chondromyxoid fibroma. Anteroposterior (A) and lateral (B) radiographs of the left leg of an 8-year-old girl demonstrate a radiolucent lesion extending from the metaphysis into the diaphysis of the tibia,with a geographic type of bone destruction and a sclerotic scalloped border

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