Normal Anatomy Ossification 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 tilt 5-10° caudad if thin leg, 5-10° cephalad if thick leg Indications fracture joint alignment OA = PA view preferred over AP 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 tilt 5-10° caudad if thin leg, 5-10° cephalad if thick leg 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 Radiographic 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 Normal knee growth = occurs until 14yo in F + 16yo in M proximal femur = 3 mm/yr distal femur = 9 mm/yr proximal tibia = 6 mm/yr distal tibia = 5 mm/yr Normal progression of varus/valgus <1 yo = varus 1 yo = neutral 3 yo = peak valgus (20°) 7 yo = normal valgus (< 12°) 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 Pediatric Distal Femoral Physeal Fracture Recommended views AP lateral oblique stress radiographs to look for physis opening if there was suspicion of physeal injury have fallen out of favor due to risk of physeal damage, patient discomfort, and possible need for sedation MRI or ultrasound have replaced stress radiographs in this setting Findings physeal widening normal 3-5mm direction of displacement suggestive of mechanism of injury anterior displacement due to hyperextension posterior displacement due to hyperflexion medial displacement due to valgus lateral displacement due to varus Treatment criteria nonoperative treatment acceptable if non-displaced closed reduction with percutaneous fixation and casting if displaced smooth K-wires if physis must be crossed lag screws if large Thurston-Holland fragment allowing avoidance of crossing the physis ORIF if irreducible SH I/II SH III/IV with weight-bearing articular involvement Pediatric Tibial Eminence Fracture Classification = modified Meyers & McKeever Modified Meyers and McKeever Classification Type I Nondisplaced (<3mm) Type II Minimally displaced with intact posterior hinge Type III Completely displaced Type III+ Type III fracture with rotation Type IV Completely displaced, rotated, comminuted Recommended views AP lateral intercondylar Treatment criteria nonoperative treatment acceptable if non-displaced/reducible type I/II ORIF vs. all-arthroscopic fusion if irreducible type III/IV Pediatric Tibial Tubercle Fracture Classification = Ogden Ogden Classification (modification of Watson-Jones) Type I fracture of the secondary ossification center near the insertion of the patellar tendon Type II fracture propagates proximal between primary and secondary ossification centers Type III coronal fracture extend posteriorly to cross the primary ossification center Type IV fracture through the entire proximal tibial physis Type V periosteal sleeve avulsion of the extensor mechanism from the secondary ossification center Modifier: A (nondisplaced), B (displaced) Recommended views AP lateral Optional views internal rotation view will bring the tibial tubercle into profile consider contralateral knee views in pediatric fractures Findings widening or hinging open of the apophysis fracture line may be seen extending proximally and variable distance posteriorly anterior swelling may be the only sign in the setting of a periosteal sleeve avulsion (type 5 injury) evaluate for possible patella alta Treatment criteria nonoperative indications type I injuries or those with minimal displacement (< 2 mm) operativet indications type II-IV fractures - need to visualize joint surface for perfect reduction and evaluate for intra-articular pathology soft tissue repair for type V fractures Pediatric Patella Sleeve Fracture Recommended views AP lateral tangential Findings small flecks of bone adjacent to superior or inferior pole diagnosis may be missed because the distal bony fragment is not readily discernible on radiographs slight anterior tilt of superior pole seen with proximal fractures patella alta for distal fractures (most common) patella baja for proximal fractures Treatment criteria nonoperative treatment acceptable if non-displaced with intact extensor mechanism ORIF if > 2-3mm displacement or disrupted extensor mechanism Pediatric Proximal Tibia Epiphyseal Fracture Recommended views AP lateral Optional views oblique varus/valgus stress but risk of injury to physis Findings displacement of fracture fragments Salter-Harris classification Treatment criteria nonoperative treatment acceptable if non-displaced stable SH I/II closed reduction and pinning if unstable SH I/II ORIF if SH III/IV Pediatric Proximal Tibia Metaphyseal Fracture Recommended views AP lateral Findings incomplete vs. complete presence of proximal fibula fracture, which may indicate a more unstable fracture pattern Treatment criteria nonoperative treatment acceptable if non-displaced reducible open reduction and casting if unable to be reduced