Knee Injury

Pain in knee PLUS

Ottawa Knee Rules

X-rays

>55 yearstender head of fibula / patellaactive knee flexion <90°inability to weight bear 4 steps immediately and at time of assessment

Nearly 100% sensitive for significant fracture; 50% specific; XR use by 25%; waiting times and cost; also can be used in children

Oblique views for tibial condyles; tunnel view for intercondyle; skyline patellar for vertical patella fracture; significant fracture in 6%, insignificant fracture in 0.5%Secondary ossification centre of patella is at superior pole (begins at 3yrs, closes at 15yrs); fabella/sesamoid in lateral head gastrocnemiusAP: <5mm of tibial condyle should be seen lateral to line from lateral femoral condyle to medial proximal fibular shaftCT: helpful if fracture of articular surfaceMRI: for STI (80% sensitive for ACL; 95% sensitive for all types of injury)Lipohaemarthosis: 10% have osteochondral fracture (60% in adolescents); if no #, 70% have ACL injury; 20% have MCL/LCL injury; 9% have PCL injury; in adolescents, 50% have intra-articular FB, 50% have meniscal tear

Knee Dislocation

Epidemiology: requires much force; can be Anterior: most common, 40%; tibia anterior Posterior: 33% Medial: 4% Lateral: 18% RotatoryUsually med and lat quads remain intact; reduction occurs spontaneously pre- hospital in 65% (but still need to evaluate for vascular injury)

Angiography if: distal pulses, abnormal ABI (if abnormal examination, 40% have a vascular injury)Management: reduction via longitudinal traction splint in 20° flexion and admitComplications: 20-30% are open; single cruciate injury in 85%, both in 70%, med / lat collateral in 40-60%; intra-articular fracture in 25%; popliteal vessel in 35-40% (presence of distal pulses doesn’t exclude injury; ?do arteriogram in all patients; if normal pulse before and after and normal ABI, can just do serial exams); high risk of compartment syndrome (may be delayed after reduction); peroneal nerve injiry in 25-35% ( foot drop, altered sensation lateral foot); 80% risk of amputation if reduction delayed >8hrs

Patella Dislocation

MOI: twisting on extended knee or direct blow; often due to patellofemoral dysplasia, hypoplastic vastis medialis, shallow trochlear groove, genu valgum; 30% have recurrent, 50% ongoing patellofemoral symptomsExamination: 60% have abnormal extensor mechanism, high riding patellar; usually dislocates laterally; patellar apprehension sign (knee flexed at 30°, firm lateral pressure to patella)Complication: torn medial joint capsuleManagement: push medially on patella while extending knee using element of surprise cast or zimmer splint 2-4/52 (minimal immobilisation if recurrent)

Patella Fracture

MOI: direct blow, fall on flexed knee, forceful contraction of quadsTransverse: 80%; more likely to be displaced and associated with disrupted extensor mechanism Examination: loss of SLRManagement: if undisplaced, POP or Zimmer splint 6/52; if >3mm displaced, ORIF

ACL Injury

Lateral condyle of femur anterior intercondylar eminence of tibia (may be associated with avulsion # here = Segond # (see X-ray above))Prevents: anterior movement of tibia on femur; stabilises knee in extensionTest: Lachman (85-95% sensitivity, 100% specificity; >5mm positive) Anterior drawer (60% sensitivity, 65% specificity; >6mm positive) lateral pivot shift (40-70% senstivity) knee arthrometer (95% sensitivity)Epidemiology: most commonly injured ligament; accounts for 70% haemarthroses; associated with MCL/LCL/meniscal injury in 50%MOI: rotational, hyperextension, deceleration snap/popComplication: medial meniscal tearMng: OT

PCL Injury

Medial condyle of femur posterior intercondylar eminence of tibia (may be associated with avulsion fracture here)Prevents: posterior movement of tibia on femur; stabilises knee in flexionTest: Godfrey’s sign posterior drawer (55-85% sensitivity)Epidemiology: rarely isolated; associated with hip injury, femoral and tibial fractureMOI: blow to leg with flexed kneeMng: may be conservative if isolated injury

MCL Injury

Medial epicondyle of femur medial proximal tibia (7cm from joint) (also attached to medial meniscus)Epidemiology: most common isolated ligament injury; may be associated with ACL injuryMOI: abduction, flexion, internal rotation; rupture if >1cm laxity without endpointMng: conservative, unless other ligament involved

LCL InjuryLateral epicondyle of femur lateral fibula? (separated from lat meniscus by popliteus tendon)MOI: adduction, flexion, external rotation; rupture if >1cm laxity without endpointComplication: peroneal nerve injMng: conservative, unless other ligament involved

Meniscal InjuryMedial mensicus 2x more common; most are posterior aspect of meniscusTest: Bragard’s sign (medial) McMurray’s test (50% sensitvitiy) Apley compression / Grind test (50% sensitivity)

Baker’s Cyst Protrusion of synovium and synovial fluid into semimembranous bursa; popliteal fossa ache; palpable bulge; do USS; symptomatic treatment