NORMAL ANATOMY Osteology Distal femur anterior/posterior view lateral view Proximal tibia anterior/posterior view Patella anterior/posterior view Attachments Muscle anterior view posterior view lateral view Ligament/tendon anterior/posterior view lateral view RADIOGRAPHIC VIEWS AP/PA view Positioning patient supine (AP) vs. prone (PA) knee extended + leg IR 3-5° beam aim 1.5cm distal to apex of patella Indications fracture joint alignment OA PA view preferred over AP view weightbearing view preferred over non-weightbearing view Critique symmetrical femoral + tibial condyles fibular head should be bisected by the tibia visualization of intercondylar eminence in intercondylar fossa Lateral view Positioning patient rolled lateral (mediolateral) = lateral decubitus on ipsilateral side + knee flexed 20-30° horizontal ray (lateromedial) = supine + knee extended beam aim 2.5cm distal to medial epicondyle tilt 5-7° cephalad (if rolled lateral) Indications patella fracture = horizontal ray view to avoid displacement patella alta/baja = requires knee in 30° flexion trochlear dysplasia OA joint effusion Critique visualization of suprapatellar fat pad = via knee flexion < 30° appropriate IR/ER superimposition of posterior aspect of femoral condyles superimposition of fibular head + tibia open patellofemoral joint no visualization of adductor tubercle appropriate cephalad angulation = open tibiofemoral joint Oblique view Positioning patient AP = supine + knee extended + leg IR/ER 45° PA = prone + knee flexed 10° + leg IR/ER 45° beam aim 1.5cm distal to apex of patella Indications fracture = femoral condyle, patella OA intercondylar fossa pathology = loose bodies Critique superimposition of patella + ipsilateral femoral condyle asymmetrical tibiofemoral joint spaces Tangential view Positioning METHOD PATIENT BEAM Sunrise/Settegast supine vs. prone knee flexed 90° inf-sup 10-20° cephalad Hughston prone knee flexed 50-60° inf-sup 45° cephalad Merchant supine knee flexed 40° sup-inf 30° caudad Laurine semi-recumbent knee flexed 30° inf-sup 30° cephalad Indications patellar malalignment trochlear groove depth OA vertical patella fracture Critique visualization of femoral condyles + trochlear groove no superimposition of patella + femur open patellofemoral joint Intercondylar view Positioning METHOD PATIENT BEAM Beclere supine knee flexed 40° AP 40° cephalad Camp Coventry/Tunnel prone knee flexed 40° PA 40° caudad Holmblad erect vs. kneeling knee flexed 70° PA 0° Indications OCD = displaced cartilage congenital slipped patella = flattening/underdevelopment of lateral femoral condyle hemophilia = intercondylar widening intercondylar fossa pathology = loose bodies Critique superimposition of patella + ipsilateral femoral condyle asymmetrical tibiofemoral joint spaces NORMAL FINDINGS Normal anatomy Normal variants fabella sesamoid bone in lateral head of gastrocnemius best seen on lateral view cyamella sesamoid bone in popliteus tendon usually present in lateral aspect of distal femur in popliteal groove best seen on AP view cortical desmoid cortical lucency in posteromedial aspect of distal femur represents origin of medial head of gastrocnemius + insertion of adductor magnus seen in adolescents (10-15 yo) bipartite/tripartite patella usually superolateral with smooth margins double-layered patella rare form of bipartite patella multiple fragmented patella with smooth well-corticated borders pathognomonic for multiple epiphyseal dysplasia CLINICAL PEARLS Ottawa knee rules XRs are indicated if any of the following criteria are met > 55yo TTP of fibular head isolated TTP of patella inability to flex knee 90° inability to bear weight, i.e. ambulate >4 steps Knee effusion Fluid density in suprapatellar pouch + around Hoffa’s triangle (anterior femoral condyles) can estimate volume of effusion from width of suprapatellar pouch Anterior displacement of patella Lipohemarthrosis Bowing vs. blurring of posterior aspect of quads tendon Joint space widening Bulging of posterior fat lines Displacement of fabella Distal femur fracture Recommended views AP lateral Optional views traction views AP, lateral, and oblique traction views can help characterize injury but are painful for patient adjacent joints always obtain views of joint above and below conralateral femur consider views of contralateral femur for pre-operative planning and templating Findings Hoffa fracture intra-articular supracondylar distal femoral fracture in the coronal plane may be seen on lateral view in elderly patients, evaluate for any pre-existing knee DJD Treatment criteria nonoperative treatment rarely indicated but can attempt if: non-displaced non-ambulatory multiple medical co-morbidities retrograde IM nail if supracondylar fracure osteoporotic bone ORIF if intra-articular displaced nonunion distal femoral replacement if unreconstructable fracture fracture around prior total knee arthroplasty with loose component Patella fracture Recommended views AP lateral best view to see transverse fx tangential best view to see vertical fx Findings fracture displacement degree of fracture displacement correlates with degree of retinacular disruption patella alta Treatment criteria nonoperative treatment acceptable if intact extensor mechanism = able to perform straight leg raise non-displaced/minimally displaced vertical fracture ORIF if failed extensor mechanism open fracture articular step-off > 2mm displacement > 3mm partial patellectomy if comminuted superior or inferior pole fracture measuring <50% patellar height only if ORIF is not possible total patellectomy if severe and extensive comminution not amenable to salvage Tibial plateau fracture Recommended views AP lateral oblique oblique is helpful to determine amount of depression Optional views plateau view 10 degree caudal tilt Findings on AP view depressed articular surface sclerotic band of bone indicating compression fx abnormal joint alignment on lateral view posteromedial fracture lines must be recognized Treatment criteria nonoperative treatment acceptable if minimally displaced split or depressed fractures low energy fracture stable to varus/valgus alignment nonambulatory patients ex-fix (temporizing or definitive) if significant soft tissue injury polytrauma highly comminuted fractures where internal fixation not possible ORIF if articular step-off > 3mm condylar widening > 5mm varus/valgus instability involvement of medial plateau bicondylar Proximal tibia fracture Recommended views AP lateral ipsilateral knee, tibia, and ankle Findings proximal fragment extended, apex anterior, varus extended and apex anterior due to patellar tendon varus due to pes anserinus + anterior compartment distal fragment flexed flexed due to hamstrings Treatment criteria nonoperative treatment acceptable if < 1cm shortening < 5° varus-valgus angulation < 10° AP angulation < 10° rotational deformity > 50% cortical apposition IM nail if enough proximal bone to accept two locking screws (5-6 cm) percutaneous locking plate if inadequate proximal fixation for IM nailing