Knee imagingxray Ali Gibbs Basic rule for viewingABCs
Knee imaging-x-ray Ali Gibbs
Basic rule for viewing-ABCs • Alignment • Bones – check for fracture by carefully following bony contours • -check bone density and trabecular pattern • Cartilage and joints – joint space should be uniform in width • Soft tissues and foreign bodies
AP Should always be in weight bearing, and both knees Alignment – Lateral tibial line (lateral edge of tibia and lateral edge of the femoral condyle should be aligned) – The tibial plateau is not flat but slopes at about 15° downwards from anterior to posterior.
AP good position -Knee in full extn -Leg in neutral rotation
Femur
AP rotated The fibula head is a great indication of rotation, if the fibula head is entirely superimposedt he image is not AP
Good lateral Patient lying on the affect side Knee flexion approx 25 -30 degrees Central beam directed to the knee joint with approx 5 -7 degrees of cephalad angulation
Rotated lateral Corrected lateral
Skyline Patient positioned in supine Knee flexion approximately 45 degrees
Rosenberg View Taken in 45 -degree flexion, posteroanterior, weightbearing view of the knee with the patellae touching the image receptor. More sensitive and specific for joint space narrowing than the conventional extension weight-bearing anterior posterior views.
Notch view Supine with knee flexed to 40 degrees Used to demonstrate tibial plateau # and femoral intercondylar spaces Clinically can be used for ACL injuries (Segond fractureavulsion of lateral tibial plateau, associated with ACL injury in approx. 75% of cases)
Normal variant-fabella
Normal variant-bipartite patella
OA on x-ray K-L scores • Grade 0 -no features of OA evident • Grade 1 doubtful jt space narrowing (JSN), possible osteophytic lipping • Grade 2 definite osteophytes and possible JSN on AP WB X-ray • Grade 3 multiple osteophytes, definite JSN, sclerosis, possible bony deformity • Grade 4 large osteophytes, marked JSN, severe sclerosis, definite bony deformity
K-L scores
Typical OA findings Joint space narrowing Osteophyte Sclerosis
Severe OA (also PHx polio)
Vascular calcification
Chondrocalcinosis
Rheumatoid Arthritis Symmetrical changes
Enchondroma
Bone Island
Bone island (enostosis) • Benign bone tumour normally pain free-rarely requires treatment • Difficult to distinguish radiologically from an osteoid osteoma, osteoblastoma (benign but often require treatment) and low grade osteosarcoma (malignant)more suspicious in history of malignancy • Normally grow within medullary canal of bone • Typically sclerotic, round-to-ovoid intramedullary foci. The long axis of the bone island is aligned parallel to the long axis of the bone. • Composed of cortical bone, so demonstrate low signal intensity on all sequences of MRI scans.
Enchondroma
Enchondroma • Benign bone tumour begins in the cartilage found inside the bones • Rarely cause symptoms often undiagnosed until xray taken for other reason • Majority do not require treatment, however can weaken bone if multiple tumours • Most common in patients btn 10 -20 years, and in small bones of hand; also femur, tibia and humorous • Can be difficult to distinguish from low grade chondrosarcomas and can transform to this-be suspicious if painful
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