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