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Musculoskeletal Diseases and Disorders: Knee and Patella PTP 521.

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1 Musculoskeletal Diseases and Disorders: Knee and Patella PTP 521

2 Fractures Knee Ottawa Rules A knee x-ray is only required for knee injury patients with any of these findings: – age 55 or over – isolated tenderness of the patella (no bone tenderness of the knee other than the patella) – tenderness at the head of the fibula – inability to flex to 90 degrees – inability to weight bear both immediately and in the casualty department (4 steps - unable to transfer weight twice onto each lower limb regardless of limping). 2

3 FRACTURES OF THE KNEE AND PATELLA Fractures of the Distal Femur Classified by location Supracondylar: occur superior to the femoral condyles. Common patterns are comminuted, impaction, linear, with or without displacement 3

4 Intercondylar: Occurs between the medial and lateral femoral condyles. Fracture pattern is commonly called a "Y" fracture. Condyles split apart from each other and from the shaft of the femur. 4

5 Condylar Usually linear and involves only one femoral condyle 5

6 Fractures of the Proximal Tibia Most frequent occurrence is at the medial and Lateral tibial plateaus with the lateral plateau most often involved. -difficult to see and treat. Mechanism of injury is a varus or valgus force combined with axial compression. Generally considered to be impaction fractures. 6

7 Because of the difficulty in viewing the tibial plateau, conventional tomography is needed in addition to the routine x-rays. A classification system has been developed to identify the 6 most common fracture patterns. 7

8 Tibial Plateau Fractures Two systems: book has the Hohl system highlighted very well. Second system is the scharzker method. The web site above has a great representation of the Scharzker classification with a unique way of viewing the CT scans. The cursor can move over the radiograph and the picture below shows the corresponding CT view. These two systems are not very different. 8

9 Comparison Hohl ClassificationSchatzker Classification Type I Type II Type III Type IV Type V Type VI Same as Hohl Type I Type III Type II Same as Hohl Type IV Same as Hohl Type V Same as Hohl Type VI Main difference between the two classifications is the placement of Type II and Type III which are switched in the two classification types. Be sure you see which classification is being used when dealing with a tibial plateau fracture to understand the bone dysfunction. 9

10 Hohl System Hohl Type I: nondisplaced vertical split fracture of the lateral tibial plateau caused by a pure valgus force Schatzker Type I: Pure split on lateral side 10

11 Hohl Type II: a local depression of the lateral tibial plateau caused by a combination of axial and valgus forces Schatzker Type III: Pure central depression - Lateral condyle 11

12 Hohl Type III: a displaced vertical split fracture with depression at the lateral plateau, caused by a combination of valgus and axial forces and often associated with a proximal fibula fracture. Schatzker Type II: Split with lateral depression 12

13 Hohl Type IV: a displaced depressed fracture of the medial plateau, caused by varus and axial forces Schatzker Type IV: fractures of medial condyle 13

14 Type V: a vertical split fracture of the anterior or posterior aspect of the tibial plateau, caused by axial forces Schatzker Type V: Bicondylar fractures Continuity of metaphysis & diaphysis maintained 14

15 Hohl Type VI: a displaced, comminuted fracture of both condyles, caused by axial forces, often associated with proximal fibula fractures Schatzker Type VI: Dissociation of metaphysis & diaphysis in addition to plateau 15

16 Fractures of the Patella MOI: direct trauma from falls or blows or indirect trauma from tension forces. -change in force, action of muscle. Direct trauma: – Patella fractures as it compresses against the femur. – Most frequent pattern is a transverse linear fracture line through the mid-region of the bone. – Vertically oriented fractures and comminution are also seen. Avulsion fractures of the patella occur as a result of indirect trauma 16

17 Patellar Fracture Patterns 17

18 Patella Fractures Patella fractures – Lateral view – AP view – Sunrise view – Patella Alta – Avulsion fracture of patella ligament 0-overview 18

19 AP and Lateral Views of the Displaced Transverse Fracture of the Patella overview 19

20 Sunrise view: MRI On the left is a patella dislocation, high signal intensity on the lateral side View on the right is a bipartite patella. Can be confused with a fractured patella 20

21 Full thickness fissure of the patella articular cartilage 21

22 Joint effusion Transverse View, fast spin echo T2-weighted fat saturated MR Normal cartilage with joint effusion surrounding it 22

23 Joint Dysfunctions of the Knee Rheumatoid Arthritis: discussed under wrist and hand Rheumatoid arthritis. Anteroposterior knee radiograph shows diffuse uniform joint space narrowing. Bone on Bone, uniform narrowing. Jacobson J A et al. Radiology 2008;248:

24 Osteochondritis Dessicans Definition: avascular necrosis of the condylar epiphysis of the femur Medial femoral condyle involved in 75% of the cases, lateral condyle can also be affected, results in a osteochondral fracture 24

25 Etiology: traumatic – Caused by impingement of the tibial spine on the femoral condyle – Or a loss of circulation to the osseous tissue of the epiphyseal plate – Or an avulsion of the proximal attachment of the PCL 25

26 SX: – aching pain in the knee at rest – worse with weight bearing activities – insidious onset – episodes of knee joint locking Signs: – antalgic gait pattern – knee joint effusion – restriction in range of motion present 26

27 Radiographs: – AP, lateral, and tunnel will show a lesion that appears like a half moon defect on the subchondral bone RX: – Decrease or elimination of WB with immobilization 27

28 Osteonecrosis: Avascular necrosis of the knee occurring in adults, Typically women age 50 years or more. Medial compartment of the knee and femoral condyle more involved than tibial condyle. 28

29 Osteoarthritis. Jacobson J A et al. Radiology 2008;248: ©2008 by Radiological Society of North America Osteoarthritis: joint space narrowing, sclerosis, and osteophyte formation (arrow) predominately involving the medial compartment. 29

30 DJD/OA of the knee Standing AP view of the knee’s – Weight Bearing Important. Typical finding is sharpening of the tibial spines Narrowing of the medial compartment 30

31 This view shows osteophyte formation on the tibial plateau, medial side Narrowing of both the medial and lateral compartments, but more on the medial. More advanced OA 31

32 Patello Femoral OA seen in a lateral view Patellofemoral compartment narrowing Osteophyte formation on both the superior and inferior aspect of the patella Try bending this knee – Patella will have more pain in flexion (stairs), but relief in extension 32

33 Surgeries: High Tibial Ostotomy Occurs in patients with unicompartmental osteoarthritis. Usually the medial compartment with a varus deformity noted. – New but effective. Patients age is usually under 65 years of age, generally exclude patients with RA or other systemic diseases 33

34 Indications for Tibial Osteotomy Best results occur in patients under 50 years of age Body mass index greater than 25 kg per square meter? Isolated medial compartment OA, No lateral thrust at the knee, A varus deformity less than 10 dg Range of motion greater than dg 34

35 Contradictions Inflammatory arthritis: RA, Sceriatic Arthritis Significant ligamentous instability Age greater than 70years Severe patellofemoral arthritis Flexion contracture greater than 15 dg – Won’t get good contact, so bone won’t heal properly. Varus deformity greater than 15 dg 35

36 Technique: wedge resection 36

37 Goal of Surgery: Realign the weight bearing axis so that the pressure on the tibial plateau is shifted laterally into the area of the intercondylar eminence and the tibial spines rather than the medial condyle 37

38 Unicompartmental replacement Replace only one part of the knee but maintain the natural joint/bony surfaces on the other part. – Used when ACL surgery fails Generally will replace the medial compartment. To function successfully, the anterior cruciate ligament needs to remain intact 38

39 Total Knee Replacement Indications: a. Chronically disabling degenerative knee pain b. Failed conservative measures Contradictions: a. Acute infection elsewhere in body b. Charcot arthropathy or absence of sensation in the joint c. Infection within the joint d. Severe spasticity associated with contractures. 39

40 Relative contra indications a. Severely demented or bedridden patients (unless needed for transfers) b. Osteoporosis (depends on bone density of femur and tibia) c. Significant peripheral vascular disease (if it won’t heal) 40

41 Prosthetic Devices Classified as constrained, semi-constrained, or minimally constrained constrained: actually hinges, knee doesn't function as a simple hinge though and these prostheses have a high failure rate, reserved for the patients with severe instability problems or severe deformities 41

42 Semi-constrained Posterior cruciate ligament is absent or taken out as a result of the surgery. This is designed to prevent subluxation or dislocation of the tibiofemoral joint resulting from the absence of the ligaments. 42

43 Advantages and Disadvantages of the Preserving the PCL Advantages – restores more normal knee kinematics – more normal stair climbing abilities Disadvantages – excessive rollback of femur on tibia if PCL is too tight – difficult to reproduce the preoperative joint line – ligament length more difficult to balance with the collateral ligaments – more difficult to correct large flexion contractures 43

44 Minimal constrained: Reproduces the anatomical contours of the knee Relies heavily on soft tissue to provide joint stability – Usually done with younger individuals, so can freely do activities. 44

45 Surgical Preparation 45

46 TKR Rehab: “joint camp” Goal of a TKR is to provide patient with a stable, pain- free knee joint with a functional range of motion -Usually there for 4 days or less. Postoperative Problems: knee stiffness which can lead to adhesions=work on flexion. Functional considerations: need at least 90 dg of flexion to be able to do most ADL's and greater than 90 dg's is needed to go from a sitting to a standing position. 46

47 Patellofemoral Dysfunctions: Patella Instabilities Patella Dislocation: associated with an excessive lateral pull of the vastus lateralis and IT band MOI: acute trauma or twisting force with a combination of flexing femur, externally rotating femur while foot is planted 47

48 Subluxation of the Patella: same mechanisms as a dislocation Patella should mirror the condylar divot. Shifted slightly like seen is a subluxation. Over more would be a dislocation. 48

49 Factors which predispose a patient to subluxation or dislocation: 1) Q angle greater than 20 dg 2) Excessive external rotation of tibia (in prone) 3) Increased internal rotation of the femur (stand behind and look at medial hamstrings coming at you that’s IR of femur) 4) Patella alta –(high patella) considered most important, tape measure=if length of patella is shorter than distance from the posterior apex to tibia tuberosity. 5) Shallow trochlear groove 6) Small flat patella 7) Atrophy of vastus medialis (hold patella, then do a quad set, see where it is pulled, usually lateral) 8) Muscle imbalance/weakness relative to the vastus lateralis 49

50 SX and Signs SX: – onset occurs with sudden activity valgus – external rotation force Signs: – Hemarthrosis -bleeding into joint. – tenderness to palpate – apprehension to lateral patella joint movement 50

51 Chondromalacia Patella Patellofemoral tracking dysfunctions: new term (to make it seem less chronic) Progressive softening, fibrillation and finally degeneration of the articular cartilage on the underside of the patella -Seen with younger girls (13-15) Overuse syndrome with altered patellar biomechanics occurring. 51

52 Chondromalacia= SX: retropatellar pain described as aching with sitting. Signs: + movie goers sign (forced into full knee flexion for a long period of time), + full knee flexion test (takes 30 to 60 seconds for achy pain to start) 52

53 Stages: I - IV I: swelling and softening of the cartilage II: fissuring w/in the softened areas III: fasciclations of articular cartilage almost to level of subchondral bone IV: destruction of cartilage w/ subchondral bone exposed – Histologically Stage IV is virtually indistinguishable from DJD 53

54 54

55 Larsen-Johansson's Disease Necrosis of the patella poles – occurs in children 8-13 years of age etiology unkown, insidious onset 55

56 SX and Signs SX: – pain with resisted extension of the knee, – pain with kneeling, – pain with activity Signs: – swelling and tenderness to palpation over the inferior pole of the patella X-ray: may or may not show fragmentation of the bone near the affected pole 56

57 Musculotendinous Dysfunctions of the Knee Osgood Schlatter's Disease: Tibial Apophysisitis -inflammation of the tibial tuberosity, which goes bone growth. Develops when the epiphysis undergoes the transition from cartilage to bone. Develops in the patella tendon/bone insertion -more cosmetic, then chronic pain. 57

58 Osgood Schlatters Disease Traction on the patella ligament results in microfractures. The body tries to heal itself and an outgrowth of the tibial tuberosity occurs. Occurs in males more than females, ages – During a growth period Differential Diagnosis: Mechanical dysfunction, mimics patellar tendonitis or patellofemoral pain syndrome 58

59 SX and Signs Sx: – pain in the region of the tibial tubercle – related to activity particularly sports – pain relieved by rest – hurts to kneel Signs: – swelling over the tibial tubercle – tenderness to palpation over the tibial tubercle 59

60 Radiographs: lateral view may show irregular ossification or fragmentation of the tibial tubercle RX: Rest, may try bracing to give patella tendon some assist Avoid resisted knee extension activities until the pain has gone away. Time is usually 6-8 weeks, may cast Surgery – rare *Issue how to keep kid from running and jumping when pain in minimum. 60

61 Tendonitis Patella tendonitis or jumper's knee: SX: – pain during activity, – pain after activity, – pain with sitting for a long period of time – tenderness noted at inferior pole of patella Signs: – tenderness to palpation, – pain with resisted knee extension – swelling over the patella tendon region – pain with passive stretch 61

62 Quadriceps Tendonitis Superior pole of the patella at the tendon junction. Occurs in sports that require a lot of running and jumping or acceleration - deceleration activities like soccer or basketball SX: – pain during activity – pain after activity Signs: – tenderness to palpate over the superior pole of the patella – pain with resisted knee extension – pain with passive stretch of the quadriceps 62

63 Iliotibial Tract Tendonitis Friction between the underlying structures and the iliotibial tract, occurs in runners or patients whose occupation or hobbies lead to a tight iliotibial tract. SX: – pain with activity – pain over the lateral thigh closer to the knee Signs: – + Ober's test – pain with resisted abduction – tenderness to palpate over the lateral epicondyle 63

64 Popliteus tendonitis Develops with excessive downhill running, excessive squatting activities -X-cross country, squatting. 64

65 Inert Tissue Dysfunctions of the Knee Ligament Medial Collateral Ligament a. MOI: valgus force applied to the lateral aspect of the knee with the foot fixed, knee in extension b. Less common MOI: knee in slight flexion (less than 90 dg), or twisting motion occurs 65

66 Symptoms and Signs SX: – mild tenderness at medial joint line – swelling Signs: – Grade I, II, or III laxity with valgus stress, – AROM is painful near the end of extension – edema present – point tender at adductor tubercle and/or medial joint line – ALWAYS check it in the position that it was injured in, also before inflammation or after it goes down. 66

67 Stress Test Analysis Mild medial laxity with valgus stress, Knee in full extension: damage to posterior oblique ligament and capsular ligament Gross instability at full extension: check ACL and PCL to make sure they are tight Empty end feel or indistinct end feel: secondary restraints are holding the knee, ligament is grade III 67

68 Medial Collateral Ligament Ligaments turn up as BLACK Coronal Images used to evaluate MCL tears Proton density coronal image – arrows Show ligament as thin, well defined, low signal intensity from medial femoral condyle to the medial tibial metaphysis overview 68

69 Lateral Collateral Ligament MOI: Varus force from the medial side of the knee. – Isolated injuries are rare because of ligament's location posterior to the axis of the knee joint. – Not as commonly injured, as very stable. – Usually injured as a torsional overload that also affects the cruciate ligaments 69

70 Sx and Signs SX: lateral knee pain Signs: – varus laxity in extension and flexion – numbness or tingling if nerve root is involved: common peroneal 70

71 Oblique orientation, low signal structure – white arrow Inserts onto fibular head Avulsion fracture of the fibular head may be seen on plain film radiographs with a LCL injury overview 71

72 LCL and MCL tear m/article/ overview LCL is outside the capsule, A tear in the LCL does not Cause as much effusion as A MCL tear. You will not see An increased signal intensity Around the ligament as you do in an MCL tear. See figure to the right. 72

73 Anterior Cruciate Ligament: MOI: combination of valgus and external rotation forces applied to the knee while foot is in a closed pack position Less common MOI: excessive internal rotation and hyperextension combination – non contact injury in which sudden limb deceleration is accompanied by a contraction of the quads producing damaging force moments – Commonly the MOI for woman. 73

74 ACL Tear Arrow’s point to the tear Less formation of the tendon 74

75 Non visualization of an ACL 75

76 Triad of images showing an ACL tear Top left: T2 Sagittal view Top right: T2 coronal view Bottom: T1 coronal view, overview 76

77 Anterior Cruciate Ligament 77

78 SX and Signs SX: Patient reports a "pop" at time of injury Knee swelling within one hour after injury Hemarthrosis within 12 hours Signs: + Lachman's + pivot shift test + anterior drawer test Hamstring muscle spasm: can give a false negative as they protect any movement from anterior drawer. Inability to fully weight bear on affected side Weakness and knee giving way are frequent occurrences 78

79 Chronic problem Frequent episodes of knee giving out. Pain and effusion with specific activities that stress knee such as cutting and pivoting RX: depends on the degree of tear, Will generally wait 2-3 weeks until the swelling has decreased before going in and assessing the ligament MRI is diagnostic as is arthroscopic surgery Surgery: Type of graft used will depend upon the physician. Great controversy in the literature regarding the graft type. 79

80 Patella - Tendon Graft: Central third of the patella tendon is taken to use as a graft, so quads will be affected. Considered to be 57% as strong as original ACL at 3 months and 87% as strong at 12 months. – At first will decrease in strength, but eventually will remodel and become stronger. Some take the tendon from the opposite side, as will have balance out, but now will have issues on both side. 80

81 Two type of Patella Tendon grafts: – Injured leg. Have to deal with two injuries then, a decrease in the quad mechanism and the ACL repair – Second is taken from the uninvolved leg. Gives a strong patella tendon on the ACL side but a weaker tendon on the opposite side (Shelbourne Procedure) 81

82 Semitendinosus and Gracilis Grafts Provide weaker initial fixation and have a more prolonged and variable rate of fixation into the bone than does the central third patella grafts. Used when there is a significant incidence of patellofemoral and anterior knee pain associated with the injury – Weakening the hamstring. 82

83 These tendons can be removed, doubled over, and then used to replace the ACL. These tendons are easier to harvest than the patellar tendon, they require smaller drill holes in the femur and the tibia for fixation, and they do not predispose patients to patellar tendinitis. 83

84 Types of Grafts 84

85 ACL Patella Tendon Graft Surgery 85

86 Allografts: Cadaver grafts Indications: Failed autograft surgery Significant patellofemoral arthrosis Narrow patella tendon Patients who don't want to use their own tissue 3 areas of concern: 1. Immune reaction 2. Potential disease transmission 3. Remodeling and effect on mechanical properties 86

87 Posterior Cruciate Ligament MOI: anteromedial blow to the flexed knee or a fall onto the knee with foot and ankle plantarflexed Common component is the posteriorly directed force on the proximal tibia which pushes the tibial plateau posterior on the femoral condyles 87

88 PCL: All three images should be used, sagittal, coronal and axial T1 Coronal Image Darker arrow is the PCL and is a lower intensity signal than the ACL Lighter arrow is the ACL overview 88

89 Sagittal View Proton dense sagittal image Insertion site (arrows) is posterior to the tibia articulating surface / overview 89

90 Avulsion fracture of the PCL as demonstrate on an AP radiograph overview 90

91 Interstitial tear of the PCL A: proton density sagittal image B: T2-weighted sagittal image e/ overview 91

92 Mid substance tear of the PCL- large arrow Proton dense-weighted sagittal view Intact PCL proximally, tear, edema noted mid PCL Ligament of Humphrey – small arrow overview 92

93 SX and Signs: Sx: – Difficulty weight bearing – Painful – Instability with stairs and inclines – Recurrent swelling Signs: – ROM is usually WNL – Painful on end range flexion – Extensor lag present (tibia drops below the femur) – + posterior drawer test – + tibial sag test – + hughston test 93

94 Surgery Surgery is controversial if only PCL is ruptured, Grade I PCL injuries with less than 5 mm of increased posterior translation of the tibia are managed non-operatively. 94

95 Surgical Reconstruction Surgical reconstruction is recommended for isolated PCL disruption that result in 10 mm if increased posterior tibial translation. Also used with PCL injuries combined with injury to other ligamentous structures 95

96 Inert Structure Dysfunctions Meniscus: Medial meniscus is more frequently injured than the lateral meniscus. (similar to SLAP lesions of the GH) Location of the tear will dictate the response to injury a. periphery: good repair, vascular, get a fibrocartilage scar tissue b. central portion, avascular, poor repair 96

97 Tears: MOI: traumatic, – occurs in the 13 to 40 year olds, – occurs with activity that may or may not be contact related – non-contact: acceleration or deceleration stresses combined with a sudden change in direction, squatting or twisting – produces a longitudinal or transverse vertical tear 97

98 Types of Tears Stoller, D. Pocket 98

99 Types of Tears 99

100 Vertical Longitudinal Tears Most frequent, Medial 2.5:1 greater incidence than lateral meniscus peripheral tear Greater than 1 cm in length Unstable with stress Causes symptoms Treat with surgery – short, less than 5mm, full thickness to partial thickness – stable, rarely cause symptoms, no surgery 100

101 Meniscal Tears: Longitudinal Tears Axial illustration of a full- thickness longitudinal tear of the posterior horn. The meniscus is viewed from above in (a), sagittal in (b), and coronal in (c). A = anterior, L = lateral, M = medial, and P = posterior. overview 101

102 Longitudinal Tear of the Meniscus Coronal T2 image (with fat suppression) shows a displaced fragment (arrow) of medial meniscus into the intercondylar notch of the knee. Also known as a bucket handle tear share?id= %253APhoto%253A

103 Vertical Transverse tears Radial tears, less common, almost always the middle third of the lateral meniscus Stable less than 5 mm Surgery if it causes symptoms 103

104 Radial Tear Axial illustration of a full-thickness radial tear of the posterior horn. The meniscus is viewed from above. overview 104

105 Degenerative tears Horizontal cleavage or flap tear. Increase incidence in age over 40, No specific injury or minor degree of stress can cause the tear. Can occur in either meniscus, associated with degeneration of the articular cartilage After age 40, will often have a horizontal splitting as a result of bending, squatting, turning and twisting over the years. Horizontal lesion seen in people over age of 55, not always symptomatic. More common in the medial meniscus, usually occurs at the junction of the middle and posterior one-third 105

106 Horizontal Tear of Posterior Horn Axial illustration of a full- thickness horizontal tear of the posterior horn. The meniscus is viewed from above. Not the same as the radial tear, goes through the substance of the meniscus in a horizontal, not vertical line overview 106

107 Posterior Horn Tear: Horizontal Fat-suppressed proton density- weighted sagittal images reveal a horizontal tear of the posterior horn of the medial meniscus (arrows), extending to the tibial surface. 107

108 Flap tear Axial illustration of an oblique (parrot beak) tear of the posterior horn. The meniscus is viewed from above. In B, image 1 is most lateral, image 2 is middle, and image 3 is most medial. In C, image 1 is most anterior, image 2 is middle, and image 3 is most posterior. 108

109 Parrot Beak: Oblique Tear 109

110 SX and Signs SX: Pain at time of injury Persists and interferes with WB activity Recurrent episodes with minor stress Baker's cyst Knee is giving way Signs: Change in WB status Minimal swelling may be noted with girth measurements McMurray's or Apley's test are positive Springy end feel 110

111 RX: surgery Link between an absent meniscus and OA. Indications for surgery: – Vertical tears – Tears near the periphery of the meniscal substance – Generally intact meniscal body – Total tissue defect less than 2 cm 111

112 Synovial Plica Remnant of 3 embryonic pouches of synovial membrane which remain in the knee as excessive synovial material. Medial plica is the most symptomatic. Will tighten during knee flexion and cause a change in the normal mechanics of the patellofemoral joint. 112

113 Example: like a fine lace curtain Probably causes no symptoms, Although the elastic edge may bow-string over the bone of the femur when the leg bends and straightens Should there be an injury affecting the plica, however, the edge can thicken and then cause regular symptoms of a 'catching' pain at particular joint positions. 113

114 Examples of Synovial Plica 114

115 SX and Signs: Sx: Similar to patellofemoral pain syndromes. – Pain in the medial aspect of the knee joint – Clicking – Intermittent locking sensation on medial side – Generalized weakness – Reports of joint instability – Classic symptom is an inability to sit for prolonged periods of time Signs: must rule out meniscus and ligamentous injuries, bone injuries, radiographs, MRI, CT scans 115

116 RX Conservative treatment with NSAIDS Modalities Exercise May use transverse friction massage 116

117 Bursitis Prepatellar Bursitis: injury through direct trauma or chronic irritation such as prolonged kneeling. 117

118 SX and Signs SX: – Localized pain and swelling in the bursa – Tenderness to palpation Signs: – Swelling of the bursa – Warm to touch – Redness – Slight loss of knee flexion – Strong but painful resisted knee extension 118

119 RX: Pain and edema control Anti-inflammatories Modalities in treatment May inject corticosteroids or drain bursa 119

120 Bakers Cyst: Definition: any form of synovial herniation or bursitis involving the posterior aspect of the knee. Often occurs in conjunction with an intra-articular derangement at the knee such as a meniscal tear or ACL injury a. SX: mass behind the knee that may or may not be tender b. Signs: well defined, edematous mass on the posterior aspect of the knee c. When present, must rule out an internal derangement. 120

121 Images of Baker’s Cyst 121

122 Pes Anserine Bursitis Definition: follows a traumatic injury or unaccustomed WB exercise SX: Medial knee pain – Aching at rest – Swelling may be present on medial aspect of knee Signs: – Tenderness to palpation – Pain with resisted flexion 122

123 Common Imaging Anteroposterior View Lateral View Sunrise View of the Patella Tunnel View of the Knee MRI – Meniscus Imaging – ACL Imaging – PCL Imaging 123

124 RADIOGRAPHIC EXAMINATION OF THE KNEE AND PATELLA Anteroposterior view: Important to do weight bearing if possible. Either way, you should note if the x-rays were taken in standing or while lying supine. 124

125 Alignment: Identify the following structures distal femur medial and lateral condyles the proximal tibia fibula the patella superimposed over the distal femur 125

126 Look at joint space for the tibia and femur, well defined in both medial and lateral views 126

127 Normal knee: slight valgus alignment Medial and lateral joint spaces should be equal Femoral condyles should be aligned with the tibial plateaus Increase in valgus or a varus mal- alignment will increase stress on medial or lateral compartment, resulting in sclerosing of the femoral condyle and tibial plateau 127

128 Anteroposterior view: One of these is WB and one is N WB – how can you tell? Look at the medial joint line on right leg especially

129 AP: Bone Density Abnormal bone density: may see Osteochondral defects (OCD) on medial or lateral condyles of the femur Blue arrow points to a radioluscent cresent area on the knee: osteochondral dissecans 129

130 Cartilage Clear, wide joint space Abnormal for there to be diminished space Generally, one condyle is involved first, then both in advanced stages of OA Bone on bone – absence of meniscus 130

131 Lateral View: Views the patellofemoral joint in profile, knee is flexed anywhere's from 20 dg to 45 dg and the beam is directed from a medial to lateral direction. 131

132 Look for the relationship of the patella to the femur, can determine patella alta or patella baja 132

133 Insall-Salvati Index: PLR = PL/TL The length of the patella ligament is measured from its attachment at the patellar apex to the tibial tuberosity (TL) and should equal the length of the patella (PL) from the superior to the inferior poles. Variance greater than 20% indicates an abnormal patella position. 133

134 Lateral: Bone Density Increase in density as the condyles are superimposed on each other Medial condyle is larger and extends distally further than the lateral condyle Patella should be consistent in density 134

135 Sunrise View or Skyline View Patella appears to be the sun, rising over the horizon Axial view of the Patellofemoral joint: Gives the articular surfaces of the patella and femur. Medial and lateral facets of the patella are visible Alignment of the patella in relation to the femur – lateral, medial etc. 135

136 Note the sulcus angle of the femur: normal value of 138 degrees +/- 6 degrees shallow sulcus angles (greater degree within the angle) have been associated with recurrent patellar dislocations. 136

137 Note the congruence angle which helps to define the position of the patella within the inercondylar sulcus. Normal value is -6 degrees. Congruence value of +16 has been associated with lateral patellar subluxation 137

138 To measure the congruence angle: Find the highest point of the medial (B)and lateral (C) condyle and the lowest point of the intercondylar sulcus (A) The angle BAC, is the sulcus angle. Bisect the sulcus angle to establish the zero reference line, AO. Find the lowest point on the articular edge of the patella (D) Project line AD. The angle DAO is the congruence angle. All values medial to the zero reference line AO are designated as minus and those lateral as plus. Mean= -6 Degrees, standard deviation = 11 degrees. 138

139 Other Common Views: Axial or Tunnel view of Intracondylar fossa: Taken in a prone position, will view the intercondylar fossa, and the posterior aspects of the knee joint. x-ray beam is projected in a posterior to anterior direction 1,2 are intercondylar eminences 3,4 are tibial plateaus hd/mbchb/adolescent/knee2.html 139

140 MRI Knee joint MRI is one of the most frequently requested imaging study in musculoskeletal radiology Comprehensive, non-invasive view of the meniscus, ACL, PCL, medial and lateral collateral ligaments Sensitivity and Specificity of 90-95% for the meniscus and almost 100% for the cruciate ligaments. (Helms, 2009) 140

141 Images Sagittal Sequences give the most information on the knee – Short TE will help with imaging the meniscus – Fast Spin Echo – proton density (FSE-PD) do not produce acceptable images of the knee Fat suppression – Makes the MRI image easier to view – Allows the Meniscal tears to stand out easier than without the suppression. 141

142 MRI Ligaments and Meniscus: image black whether it’s a T1 or T2 image. This MRI shows the meniscus as to triangular black blocks just under the femur. The patella ligament (tendon) images black from patella to tibial tubercle. 142

143 Meniscus A fat-suppressed proton density-weighted axial image through the knee Demonstrates the C- shaped menisci. Note the symmetrical shape of the lateral meniscus (red outline) and the asymmetry of the medial meniscus (blue outline), where the posterior horn (asterisk) is significantly larger than the anterior horn. 143

144 Sagittal fat-saturated proton density– weighted image: – Concave superior meniscal surface (arrows), which improves contact with the femoral epicondyles, and a flat undersurface, which improves contact with the tibial plateau. – The periphery (outer edges) is thicker than the central portion (arrowhead), allowing for firm attachment to the joint capsule. – Normal bow-tie appearance of the meniscal body. overview 144

145 Coronal fat-saturated proton density–weighted image: Posterior slice – Posterior horns of the medial and lateral menisci. The posterior horn of the medial meniscus (left arrow) is thicker than the posterior horn of the lateral meniscus (right arrow). – The medial portion of the posterior horn of the lateral meniscus (ie, the meniscus on top of the fibula) is directed upward obliquely, from a lateral to medial direction. This is its normal course. overview 145

146 Transverse (Intermeniscal) Ligament Axial fat-saturated proton density– weighted image Transverse (intermeniscal) ligament (arrows) connecting the anterior portions of the medial and lateral menisci overview 146

147 The ligament of Wrisberg Coronal proton density– weighted image – originating from the posterior medial horn of the medial meniscus and passing obliquely upwards (arrow) to attach to the posterolateral aspect of the medial femoral epicondyle overview 147

148 Coronal fat-saturated proton density–weighted image of the mid knee Normal appearance of the body of the medial and lateral menisci. The apices (inner portions) are the thinnest part of the meniscus and are more central in the knee joint. The periphery, meniscal bases, outer portion (arrow and arrowhead) is the thickest part and contains the blood vessels supplying the meniscus. overview 148

149 ACL and PCL: Normal Again, the ligaments will Image darker on the MRI. Note the orientation of fibers When determining the Structure These two images are taken At different depths in order To see the ligaments this clearly 149

150 ACL: Normal Views 150

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