Imaging approach to joint diseasesWerner HarmseJuly 2010

ArthritisIndicates an abnormality of the joint as the result of a degenerative, inflammatory, infectious, or metabolic process.Affects articular surfaces on both sides of jointResults in joint space narrowing

Classification of arthritidesDegenerativeOsteoarthritis: Primary, SecondaryInflammatoryRheumatoid arthritisSeronegative spondyloarthropathies: AS, Reiters, Psoriasis, Enteropathic arthropathiesConnective tissue disease: Scleroderma, SLE, Dermatomyositis Erosive OAMetabolicCrystal deposition: Gout, CPPD, etcOther deposition: Hemochromatosis, Wilsons, Alkaptonuria, AmyloidosisEndocrine: Acromegaly, Hyper-parathyroidismHaemophiliaInfectivePyogenicTBothers

Imaging of joint diseaseX-rayUltrasoundMRICTArthrographyNuclear medicine

UltrasoundMultiplanar real time soft tissue imagingHelpful in diagnosing joint effusions especially in septic arthritis, as well as other fluid collectionsAlso used in evaluating for tendonitis and tendon rupture

CTComputed tomography (CT) is effective in evaluating degenerative and inflammatory changes of various joints Findings are similar to plain film radiography, only being able to demonstrate it more clearlyMultiplanar reformations can be done with MDCTValuable in planning of surgeryIn the assessment of spinal stenosis secondary to degenerative changes, CT examination may also be performed after myelography especially if MRI is contraindicated

MRIExcellent contrast between soft tissues and bone. Articular cartilage, fibrocartilage, cortex, and spongy bone can be distinguished excellent for demonstrating synovial abnormalities in rheumatoid arthritis. Because synovitis is often accompanied by joint effusion, this too can be effectively demonstrated by MRI Occasionally, MRI may provide some additional information in osteoarthritis and hemophilic arthropathyMost important role is in evaluation of the spine. Demonstrate hypertrophy of the ligamentum flavum or the vertebral facetsGrade foraminal and spinal stenosis Evaluate degenerative and inflammatory disc disease Also very valuable in evaluating joint related injuries

Nuclear medicineUsed to evaluate the pattern of disease activity and monitor responsehow many joints are affected, which joints are the most affected, are there unsuspected sites with disease involvement) Investigate sites of possible infectionA negative bone scan is reassuring and confirms the absence of active arthritis, while a positive bone scan can demonstrate disease presence and activity before it becomes apparent on a radiograph.Bone scans have been used to predict erosions in rheumatoid disease and has also been shown to be a good predictor of disease progression in osteoarthritis

X-rays: what to look forAlignmentBoneCartilageDistributionSoft tissues

X-rays: what to look forAlignmentSubluxation and/or dislocation Common in RA and SLEBoneOsteoporosisPeriarticular osteoporosis in RAErosionsAggressive with no sclerotis margin: RA, psoriasisNon-aggressive (fine sclerotic border): gout, usually overhangingLocation: Marginal inflammatory; Central Erosive OA (gull wing)Bone productionOsteophytes: at sites of cartilage loss and degeneration typical in OASubchondral sclerosis: typical of OAAnkylosis: seronegative inflammatory arthropathies eg ASPeriosteal reaction: psoriasis, Reiters (distinguish from RA)Subchondral cystsOA and CPPD, also RA and AVN

X-rays: what to look forCartilageJoint spaceNormal joint space: Gout; or any early arthropathyEccentric narrowing: OAUniform narrowing: All othersWide joint space: early inflammatory processCalcification: CPPD

X-rays: what to look forDistributionSingle joint: Infective; crystal deposition; post traumaticHands and feetproximal: RA, CPPD, SLEDistal: Reiters(feet), psoriasis(hands), sclerodermaSymmetrical: RA, SLESI jointsAsymmetrical: Reiters, PsoriasisSymmetrical: AS, Enteropathic, Reiters, PsoriasisAlso DJD, infection, gout

X-rays: what to look forSoft tissuesSwellingSymmetrical around joint: all inflammatory, but most common in RAAssymmetrical: most commonly d.t. osteophytes rather than true swelling in OALumpy, bumpy: gout (tophus)Entire digit: Psoriasis, ReitersCalcificationSoft tissue: GoutCartilage: CPPDSubcutaneous: Scleroderma, dermatomyositis

X-raysFirst important decision to make is if arthritis is present or notAlmost all arthritides lead to joint space narrowing, except goutThen decide if it falls in the broader degenerative or inflammatory group as most a fall in one of these two.

Arthritis or not

Inflammatory vs DegenerativeJoint inflammation is characterized bybone erosions (marginal)osteopeniasoft-tissue swellinguniform joint space lossDegenerative cause of joint space narrowing is characterized byosteophytesbone sclerosissubchondral cysts or geodesasymmetric joint space narrowinglack of inflammatory features such as bone erosions

Inflammatory

InflammatoryEvaluate the number of joints involvedIf only a single joint is involved consider infective arthritisFeatures of any inflammatory arthritisBut erosions often not acutely presentJoint space may be initially widened due to effusionSeen easily with ultrasoundWidening also seen in more indolent infections i.e. TB and fungalPhemister triad in TB arthritisperiarticular osteoporosis, peripherally located osseous erosions, gradual diminution of the joint space

Progression of TB of the knee over 1 year

InflammatoryIf multiple joints are involved consider a systemic arthritisNow evaluate hands and feetIf proximal with no bony proliferation consider rheumatoid arthritisIf distal with features of bony proliferation consider seronegative spodyloarthropathies eg. AS, Reiters, psoriasis and enteropathic arthropathies

Rheumatoid arthritisWomen aged 30 60Rheumatoid factorGeneral features of inflammatory arthritisAdditionally joint subluxation and subchondral cysts may also be presentIn the hands, target sites include the MCP, PIP, midcarpal, radiocarpal, and distal radioulnar joints, with predilection for the ulnar styloid processInvolvement is usually bilateral and fairly symmetric

Rheumatoid arthritisUlnar deviation occurs at the MCP joints.Swan neck and Boutonniere deformities. In the feet, target sites include the MTP, PIP (incl 1st IP) and intertarsal jointsImportant to closely evaluate the lateral aspect of the fifth metatarsal head often 1st site of bony erosionAlso affects tendon sheaths and bursae like the retrocalcaneal bursa:Loss of the normal radiolucent triangle between the posterosuperior margin of the calcaneus and the adjacent Achilles tendon suggests the presence of bursal fluid, with subjacent calcaneal erosions indicating inflammation

Rheumatoid arthritisOther peripheral joints also affected include the knees, the hips, the sacroiliac and glenohumeral joints. Spinal involvement affects the C1-C2 articulationthe odontoid process may be erodedand the anterior atlantodens interval may be abnormally widened (3 mm in adults), especially with neck flexion

Small erosions at the 5th MTP joint

a) Normal shoulder X-rays in patient with rheumatoid arthritis. (b) Ultrasound of same patient demonstrates 1.5 cm erosion.

Synovial enhancement with Gd-DTPA. (a) Three-dimensional gradient-echo image of a wrist following IV Gd-DTPA shows extensive enhancing synovitis and distention of the synovial cavity. (b) Repeat MRI with Gd-DTPA following 3 months of disease-modifying antirheumatic drug (DMARD) therapy shows marked reduction in the amount of enhancing tissue but similar distention of the synovial cavity (note the dorsally displaced extensor tendons).

Seronegative spondyloarhtropathiesPsoriasis, AS, Reiters and enteropathic arthritides.HLA B27 usually positiveHands and feet show more distal involvement.Osseous attachment sites of ligaments and tendons are more involved than in RA.Entheseal involvement leads to increased density and irregular bone proliferation (perisotitis).Ankylosis more common

Psoriatic arthritisHallmarks signs of inflammatory arthritis combined withperiostitis, enthesitis, and a distal joint distribution in the extremitiesFindings may be bilateral or unilateral and symmetric or assymmetricHands more than feetInvolvement of several joints in a single digit, with soft-tissue swelling, produces what appears clinically as a sausage digitAggressive erosions leading to Pencil in cup appearance and resorption of terminal tuftsFuzzy/fluffy bony proliferation and periostitis Ivory phalanxMouse ears: Bone production adjacent to erosionsSI joint involvement usually bilateral may be symmetrical or not

Psoriatic arthritis. Dorsovolar radiograph of the hand of a 57-year-old woman shows the typical presentation of psoriatic polyarthritis. The pencil-in-cup deformity in the interphalangeal joint of the thumb is characteristic of this form of psoriasis.

Psoriatic Arthritis. A. Cartilage loss at the PIP joints of the 3rd, 4th, and 5th digits in this hand is apparent, with erosions noted most prominently in the 4th digit (arrow). These erosions are not sharply demarcated but are covered with fluffy new bone. Note also the periostitis along the shafts of each of the proximal phalanges. B. Advanced psoriatic arthritis. Fusion across the PIP joints of the 2nd to 5th digits. Several of the DIP joints are also ankylosed. Severe joint space narrowing at the metacarpophalangeal joints is noted.

Reactive arthritis (Reiters)Sterile inflammatory arthritis following an infection at a different siteYoung men aged 25-35Similar to psoriasis in inflammation, proliferation, periostitis and ethesitisFeet more than hands particularly MTP joints and heelsAxial skeleton may also be affected

A CT scan through the SI joints shows unilateral SI joint sclerosis and erosions (arrows), typical for psoriatic arthritis or Reiter disease.

Ankylosing spondylitisIdiopathic inflammatory arthritis96% are HLA B27+, Men aged 20 40More commonly affects axial skeletonSpine involvement is characterizedby osteitis, syndesmophyte formation, facet inflammation, and eventual facet joint and vertebral body fusion. Sacroiliac joint disease is bilateral and symmetric. Other peripheral joints, such as the hips and glenohumeral joints, may be involved.

Ankylosing spondylitisSI joints show early erosions best seen at inferior aspectsSclerosis follows with eventual ankylosisSpine involvement usually centered at thoracolumbar or lumbrosacral junctionOsteitis at anterior discovertebral junctions with erosions, sclerosis shiny corner and squaring of vertebral bodiesSyndesmophytes form with eventual fusion of the vertebral bodies (bamboo spine).Also interspinous ligament calcification

Enteropathic arthritisOccur with Crohns disease, Ulcerative colitis and Whipple diseaseSpine and sacroiliac and peripheral joints may be affected. Spine: squaring of the vertebral bodies and the formation of syndesmophytes are common features. Sacroiliitis, usually bilateral and symmetricradiographically indistinguishable from ankylosing spondylitis In addition, patients may also exhibit a peripheral arthritis, the activity of which generally approximates the activity of the bowel disease.

DegenerativeJoint space narrowing, Osteophyte formation, Bone sclerosis and Subchondral cysts are seen in the absence of inflammatory changesConsider age, joints involved and x-ray appearance to distinguish betweenTypical osteoarthritisAtypical osteoarthritis

Typical osteoarthritisResult of articular cartilage damage and wear and tear from repetitive microtrauma that occurs throughout life, although genetic, hereditary, nutritional, metabolic, pre- existing articular disease, and body habitus factors may contribute in some cases. Usually after 4th or 5th decadeTypical sitesAC joints small osteophytes from 4th decade1st CMC joint, IP joints of hands, MCP to a lesser degree, 1st MTP(joint space narrowing may be symmetrical in hands, unlike larger joints)Knee medial joint space as well as patellofemoral. Often formation of osteochondral bodiesHip superior migration

(A) Sagittal PD of pt with OA of the right knee shows involvement of the femoropatellar compartment. Note joint space narrowing, subchondral cyst (arrow), and osteophytes (open arrows). (B) Coronal T2 fatsat image shows complete destruction of articular cartilage of the lateral joint compartment (arrows), subchondral edema (open arrows), and tear of the lateral meniscus (curved arrow). (C) Sagittal T2-fatsat in another patient shows osteoarthritis of the knee complicated by multiple osteochondral bodies (arrows).

Atypical osteoarthritisOsteoarthritis, but involved joint is not one commonly affected by osteoarthritis,the severity of the findings are excessive or unusual, or the age of the patient is unusual, then other less common causes for cartilage damage and osteoarthritis should be considered.Trauma,Crystal deposition disease, Neuropathic joint, Hemophilia. Other possible causes include congenital and developmental anomalies, such as dysplasia, that disrupt normal biomechanics.

Atypical osteoarthritisTrauma (injury or repetitive stresses) most common cause, usually relatively young patient, with marked asymmetric involvementCPPD Atypical in joint distribution, excessive subchondral cyst formation and calcium deposition (chondrocalcinosis)Knee most commonly affectedRadiocarpal and 2nd & 3rd MCP jointsChondrocalcinosis of triangular fibrocartilage and menisci (also pubic symphysis and hip labrum)

Atypical osteoarthritisHaemochromatosisAlso chondrocalcinosis, with overlap of CPPD findingsMore extensive MCP involvementMetacarpal radial hooklike or drooping osteophytes are more commonNeuropathic jointLate disease is characteristic with severe joint destructionsclerosis, fragmentation, subluxation, heterotopic new bone formationEarly disease is similar to OA but distribution is characteristicMidfoot and hips in DMBilateral shoulder joints in a syrinx or spinal tumourHips in tertiary syphilis

Lisfranc Charcot Joint. Dislocation of the second and third metatarsals along with joint destruction and large amounts of heterotopic new bone are present in the foot of this diabetic patient. These findings are classic for a Charcot joint

Atypical osteoarthritisHaemophiliaRepetitive intra-articular haemorrhage may cause cartilage damageYoung patientsOsteophytes, sclerosis and subchondral cyst, but also erosionsJoint space narrowing is more symmetricalEpiphyseal overgrowthKnees squaring of patella and widening of the intercondylar notchRepeated hemorrhage may produce a large expansile and destructive abnormality known as hemophiliac pseudotumor, most commonly involving the femur and pelvisoverlap between of hemophilia and juvenile chronic arthritis; however, knee, ankle, and elbow involvement are more common in hemophilia.Remember: Any cause of arthritis can eventually end in secondary or atypical osteoarthritis

Advanced haemophilic arthropathy in the elbow

OthersJuvenile Idiopathic Arthritis (previously known as JRA)Soft tissue swelling and osteopeniaDelayed joint space narrowing and erosive changesPossible periostitis and later joint fusionOsseous overgrowth of the epiphyses due to chronic hyperemia and Bone undergrowth due to premature growth plate fusion.Three sub types:Oligo articular (Prev. pauci articular) Poly articularSystemic disease

JIAOligo-articularAffects 4 or fewer joints in the first 6 months of illness. Often ANA positive50% of JIA cases. Usually involves the knees, ankles, and elbows but smaller joints such as the fingers and toes may also be affected. The hip is not affected unlike polyarticular JRA. Usually asymmetrical

JIAPoly-articularAffecting 5 or more joints in the first 6 months of disease. More common in small girls to that of boys. Usually the smaller joints are affected, such as the fingers and hands, although weight-bearing joints such as the knees, hips, and ankles may also be affected. Can include neck and jaw as well.Usually symmetricalSystemic JIACharacterized by arthritis fever and rash Affects males and females equally.Systemic JIA may have internal organ involvement and lead to serositis

11-year-old girl with juvenile idiopathic arthritis. Anteroposterior radiograph of both knees shows bones are osteopenic. Overgrowth of medial femoral condyles and widened intercondylar notch are both recognized features of juvenile idiopathic arthritis. 8-year-old girl with juvenile idiopathic arthritis. Right hand reveals severe changes: marked osteopenia, erosions (arrows), ankylosis of carpal bones and some interphalangeal joints, and subluxation of proximal interphalangeal joints of index and little fingers.

OthersErosive osteoarthritisDistribution similar to OA in hands (IP joints)OsteophytesCentral gullwing erosionsMay end in ankylosisSLEJoint space narrowing and erosions are rareCommonly reducible MCP subluxations

Central gullwing erosions in erosive osteoarhtritisSystemic lupus erythematosus. (A) Typical appearance of the thumb in a 43-year-old woman with systemic lupus erythematosus. Note subluxations in the first carpometacarpal and metacarpophalangeal joints without articular erosions. (B) In anther patient, a 32-year-old woman with SLE, the oblique radiograph of her left hand shows dislocation at the first carpometacarpal joint (arrow) and subluxations in the metacarpophalangeal joints of the index and middle fingers associated with swan-neck deformities (open arrows).

OthersGoutJoint space narrowing only occurs lateCharacteristic erosions Punched out, overhanging edges, sclerotic margins, near joint but not specifically marginalMarked soft tissue swelling due to tophiMost common in 1st MTPAlso IP joints and tarsal bonesSoft tissue swelling from bursitis as in olecranon bursitisRadiographic findings may at times be confusing and appear quite unusual, thus it may be helpful to remember, When in doubt, think gout.

Other diseases involving jointsSynovial osteochondromatosiscaused by a metaplasia of the synoviumresults in deposition of foci of cartilage in the jointmostly deposits calcify and are seen on X-rayknee, hip, and elbow Pigmented villonodular synovitisrare chronic inflammatory process of the synovium that causes synovial proliferationswollen joint with lobular masses of synovium occurs and causes pain and joint destruction rarely calcifiesJoints with PVNS look radiographically identical to noncalcified synovial osteochondromatosisErosion in 50%: cyst-like defects of varying sizes are present which show sclerotic margins. PVNS has a characteristic appearance on MR, with low-signal hemosiderin seen lining the synovium on both T1WIs and T2WIs

Synovial Osteochondromatosis. Anteroposterior view of the hip in this patient with left hip pain shows multiple calcified loose bodies in the hip joint, which is virtually diagnostic of synovial osteochondromatosis.

Pigmented Villonodular Synovitis (PVNS). Sagittal T1W (A) and fast spin-echo T2W (B) images of an ankle with PVNS show a soft tissue mass emanating from the ankle joint, which is low signal on both sequences and has very low signal hemosiderin lining parts of the synovium, which is characteristic for PVNS.

Joint space narrowingInflammatory1 joint> 1 jointInfectionRheumatoidArthritisSeronegativespondyloarthropathiesDegenerativeTypical OAAtypical OATraumaCrystal depositionNeuropathicHaemophiliaSymmetricErosionsSoft tissue swellingAsymmetric OsteophytesSclerosisUnusualDistributionSeverityAgeProximalNo bony proliferationDistalBony proliferationOthers: JRA, Gout, SLE, erosive OA,PVNS, Synovial osteochondromatosis

ReferencesJacobson et al. Radiographic evaluation of arthritis: Inflammatory conditions. Radiology 2008; 248:378389Jacobson et al. Radiographic evaluation of arthritis: Degenerative Joint Disease and Variations. Radiology 2008; 248:737747Weisleder. Primer of Diagnostic RadiologyBrandt & Helms. Fundamentals of Diagnostic RadiologyGreenspan. Orthopaedic Imaging: A ractical approach. 4th Ed