Knee injuries

Popliteal artery injury

• Seen with femoral condyle fractures, displaced tibial plateau fractures, PCL injuries, multiple ligamentous injuries and knee dislocation
• Abnormal peripheral pulses has 79% sensitivity and 91% for arterial injuries requiring surgical intervention
  • Therefore, even with normal pulses vascular injury may exist
• ABPI and duplex USS (95% sensitive and 99% specific for vascular injury)
• Vascular surgical consult to determine need for angiography + monitoring for compartment syndrome, venous injury and arterial thrombosis

Peroneal nerve injury

• Peroneal nerve injuries
  • 50% of fibular head fractures or avulsions have common peroneal nerve injury
  • Presents with foot drop and loss of sensation over anterolateral leg and dorsum of foot

Haemarthroses of the knee

• Adults
  • 70% of those without fracture have an ACL tear
  • 20% have collateral ligament injuries
  • 9% posterior cruciate
• Adolescents
  • 60% osteochondral fractures
  • 50% have normal X-ray
  • 50% have intra-articular foreign body on arthroscopy
  • 50% meniscal tears
  • Only 10% have ACL tears

Ottawa knee rules

• X-ray if one criterion met:
  • Patient 55yo
  • Tenderness at head of fibula
  • Isolated tenderness of patella
  • Inability to flex knee to 90 degrees
  • Inability to transfer weight for four steps both immediately after injury and in ED
• Reduces ED waiting times and costs
• 100% sensitive for significant fractures
• Reduces X-ray use by 25%

Patella fractures

• Skyline view may be helpful for subtle fractures
• Bipartite patellar (8% of population) can be mistaken for fracture (typically superolateral position and bilateral in 50%)
• Transverse most common, then stellate and comminuted
• Check integrity of extensor mechanism with straight leg raise

Patella fracture

• Non-displaced with intact extensor mechanism: Knee immobiliser, rest, ice, analgesia and # clinic f/u
• Displaced >3mm, articular incongruity >2mm, disruption of extensor mechanism: ORIF
• Severely comminuted: Surgical depbridement of small fragments and suturing of tendons +- ORIF
• Open fracture: Ab, debridement and irrigation +- ORIF in OR

Femoral condylar fractures

• Includes supracondylar, intercondylar, condylar and distal femoral epiphyseal fractures
• Incomplete or non-displaced fracture – Long-leg cast and # clinic
• Displaced or any degree of joint incongruity – Long-leg cast and ortho consult for ORIF

Supracondylar fracture

• Muller classification
  • Type A – Extra-articular, transverse
  • Type B – Unicondylar
  • Type C – Bicondylar 
• All need surgical repair

Tibial spine and tuberosity fractures

• Anterior tibial spine 10x more commonly avulsed
• Positive Lachman test
• Incomplete or non-displaced: Knee immobiliser and # clinic
• Complete or displaced fracture: ORIF

Tibial plateau

• Typically older population and occult
• Lateral plateau more often fractured
• Lipohaemarthrosis common on horizontal lateral beam and may be only sign of fracture
• If cannot weight bear with normal X-ray – CT
• ACL and MCL injuries are associated with lateral tibial plateau fractures
• LCL injuries occur with medial plateau fractures
• A Segond fracture (lateral tibial condyle avulsion) = 75% specific for ACL
• Non-displaced lateral: Knee immobiliser, NWB status and # clinic
• Depression of articular surface: ORIF

Tibial plateau

• Schatzker classification
  • I – Pure cleavage of lateral tibial plateau with <4mm depression/displacement
  • II – Type I with depression >4mm
  • III – Pure depression of lateral tibial plateau (no wedge fracture)
    • IIIa – Lateral depression
    • IIIb – Central depression
  • IV – Medial tibial plateau fracture with split or depressed segment
  • V – Wedge fracture of both medial and lateral tibial plateau
  • VI – Transverse tibial metadiaphyseal fracture, along with any tibial plateau fracture

Tibial plateau

Tibial plateau management

• Type I – Conservative
• Type II
  • Non-operative if <6mm depression after traction
  • Operative if joint surface depressed >1cm (>4mm in younger people), valgus >10 degrees, closed reduction not maintained or associated posterior wedge
• Type III
  • Most low energy fractures in older people can be managed conservatively
• Type IV, V, VI
  • IV has worst prognosis. ORIF for all

Medial and lateral collaterals

• Test in 30 degrees flexion
• If laxity evident in 30 degrees flexion, do again in full extension
• Laxity to valgus stress while fully extended suggests
  • Entire medial collateral ligament complex involvement and/or cruciate/posterior capsule tear
• Laxity to varus stress while fully extended suggests
  • Posterolateral corner of knee injury or cruciate ligament involvement

Anterior cruciate ligament

• Typically deceleration, hyperextension or marked internal rotation of tibia on femur
• Pop is pathognomic with rapid swelling and sense of instability
• Lachman test (84% sensitive and 100% specific) and anterior drawer tests (62% sensitive)
• 75% of all haemarthroses are from ACL
• Associated with medial meniscal injuries
• May occur as isolated injuries (vs. PCL rarely)

Posterior cruciate ligament

• Isolated injuries are uncommon
• Usually anterior-to-posterior force on lower leg
• Posterior drawer test and sag sign

Posterolateral injury

• Difficult to diagnose
• Involves tear to popliteus-arcuate compex +- lateral collateral ligament injury +- ACL injury or PCL injury

Ligamentous injury treatment

• Isolated minor strain – Knee immobiliser, ice, elevation, NSAID’s and ambulation as soon as comfortable with 3-4 times daily ROM exercises of knee and referral for f/u
• Isolated complete rupture – AS above with straight leg quad strengthening and ROM exercises
• Professional athletes with single complete tear or patients with more than one ligament involved need orthopaedic consult for operative planning

Meinscal injuries

• Medial meniscus twice as likely to be injured as lateral
• 4/5 of tears involve the peripheral posterior aspect
• Joint line tenderness sensitivity 70% and specificity 15% in ED
• McMurray’s (50% sensitive)
• Apley Grind test 50% sensitive
• Painful locking on flexion/extension is highly suggestive
• Effusions after activity, sensation of popping, clicking or snapping, instability with activity and tenderness in anterior joint space after excessive activity all suggest meniscal tear
• If suspected, partial weight bearing and GP f/u

Locked knee

• Cannot actively or passively fully extend
• Usually torn meniscus
• DDx includes ACL rupture, patella dislocation, loose bodies or foreign body
• Procedural sedation and one attempt at unlocking by leg hanging over edge of table, knee 90 degrees flexed and then apply longitudinal traction with internal/external rotation
• Ortho consult if unsuccessful for operative arthroscopy

Knee injuries with progressive valgus force

• Medial ligament
• Medial meniscus
• Anterior cruciate
• Posterior cruciate
• Lateral tibial condyle
• Lateral ligament

Knee dislocation

• Tremendous force in hyperextension or direct posterior force to anterior tibia, force to fibula or medial femur, force to tibia or lateral femur or rotatory force
• Can be spontaneous in the morbidly obese
• Anterior dislocation in 40%, posterior 33%, lateral 18%, medial 4% and rotatory rare
• Spontaneous reduction occurs in 50% due to tremendous instability so can be missed on radiographs
• A severe injured knee with instability in multiple directions is a spontaneously reduced knee dislocation until proven otherwise

Knee dislocation

• High incidence of popliteal artery injury and common fibular nerve injury + ligamentous/meniscal tears
• Reduction is via traction then splint in 20 degrees flexion and reassess neurovascular status
• Need urgent ortho and vascular consult
• Some authors recommend arteriography for all potential knee dislocations due to high rates of injury
• Ischaemic time >8 hours = 86% rate of amputation

Knee dislocation

• Kennedy classification
  • Anterior 30-50%
    • Most common. Hyperextension, torn PCL, intimal tear of popliteal artery common
  • Posterior 25%
    • Axial load to flexed knee (dashboard)
    • 25% rate of vascular injury
  • Lateral 13%
    • Varus or valgus force
    • Torn ACL and PCL
    • Highest rate of peroneal nerve injury
  • Medial 3%
    • Usually PCL disrupted
  • Rotational 4%
    • Usually irreducible
    • Often buttonhole of femoral head through medial capsule

Patellar dislocation

• Usually from twisting injury to extended knee
• Patella displaced laterally
• Tearing of the medial joint capsule is common
• Flex hip, hyperextend knee and slide patella back in place under procedural sedation
• Residual soreness remains medially from patellofemoral retinacula injury
• Obtain X-rays to exclude a fracture, place in knee immobiliser 2-4 weeks and provide crutches with partial weight bearing, straight leg raises to strengthen quads and # clinic follow-up
• Recurrence in 15-30% of patients. Promote minimal immobilisation in these patients and refer for operative repair

Quadriceps and patellar tendon rupture

• Quadriceps rupture mostly those >40 vs.
• Patellar tendon rupture mostly <40
• Tendinitis or past/present steroid use increases risk
• Severe pain, diffuse swelling, inability to perform SLR against gravity
• Needs surgical repair and ortho consult
• Incomplete tears with intact extensor mechanism can be immobilised and referred to # clinic

Patellar tendinitis

• Jumper’s knee
• Pain at patellar tendon and worse with standing/jumping
• NSAID’s, eccentric quad strengthening exercises and activity modification
• Rule out Osgood-Schlatter

Last Updated on October 6, 2020 by Andrew Crofton