Orthopaedics: Knee
Evaluation of Knee Complaints
History
· general orthopaedic history
· also inquire: about common knee symptmns
o locking: mechanical block to extension
o –torn meniscus/loose body in joint
o pseudo-locking: limited ROM without mechanical block
o –effusion, muscle spasm after injury, arthritis
· painful clicking (audible)
o torn meniscus
· giving way: instability
o cruciate ligament or meniscal tear, patcllar dislocation
Physical Examination
· general orthopaedic physical exam (do not forget to evaluate hip)
Special Tests of the Knee
· Anterior and Polter.lor drawer tests (see Figure 39)
o demonstrate tom ACI. and PCI., respectively
o knee flexed at 900, foot immobilized, hamstrings released
o if able to sublux tibia anteriorly, then ACL may be torn
o if able to sublux tibia posteriorly, then PCL may be torn
· Lachmann test
o demonstrates torn ACL
o hold knee in 10-20" fleJ:ion, stabilizing the femur
o try to sublux tibia anteriorly on femur
o similar to anterior drawer test, more reliable due to less muscular stabilization
· Posterior sag lip
o demonstrates tom PCI.
o may give a false positive anterior draw sign
o flex: knees and hips to 90", hold ankles and knees
o view from the lateral. aspect
o if one tibia sags posteriorly compared to the other, its PCL Is tom
· Pivot shift sign
o demonstrates torn ACL
o start with the knee in atension
o internally rotate foot, slowly flex knee while palpeting and applying a valgus force
o normal knee will flex: smoothly
o if incompetent ACL, tibia willsublux anteriorly on femur at 5tart of maneuver. During flexion, the tibia will reduce and extemally rotate about the femur (the "pivot"')
o reverse pivot 5hlft (start in flmon, mernally rotate, apply valgus and mend knee) suggests torn PCI.
· Collateral ligament stress test
o palpate ligament for •opening" of joint space while testing
o with knee in full extension, apply valgus force to test MCL, apply VllrWI force to test LCL
o repeat tcst5 with knee in 20" flexion to relax joint capsule
o opening only in 20° flexion due to MCL damage only
o opening in 2° of flexion and full extension is due to MCL, cruciate, and Joint capsule damage
Test for meniscal tear
· Crouch compression test
o joint line pain when squatting (anterior pain suggests patellofemoral pathology)
· McMurray's test useful collaborative information (see Figure 40)
o with knee in flexion, palpate joint line for painful "pop/click"
o intemally robrte foot. varus stress, and extend knee to test lateral menisCUll
o externally rotate root, valgus stress, and extend knee to test medial menisCUll
X-Rays
· AP standing. lateral
· skyline - tangential view with knees flexed at 45o to see patellofemoral joint
· 3-foot standing view - useful in evaluating leg length and varusfva1gus alignment
· see Ottawa Knee Rules (Emergency Medicine, ERl7)
Cruciate Ligament Tears
· ACL tear much more common than PCL tear
Collateral Ligament Tears
· MCL tear more common than LCL tear
Mechanism
· valgus force to knee =medial collateral ligament
· varus force to knee =lateral collateral ligament
Clinical Features
· swelling/effusion
· tenderness above and below joint line medially (MCL) or laterally (LCL)
· joint laxity with varus or valgus force to knee
o laxity with endpoint suggests partial tear
o laxity with no endpoint suggests a complete tear
· test for other injuries (e.g. O'Donahue's triad), common peroneal nerve injury
Treatment
· partial tear: immobilization x 2-4 weeks with early ROM and strengthening
· complete tear or multiple ligamentous inJuries: surgtcal repair of ligamenta- not for MCL or LCL on their own
Maniacal Tears
· medial tear much more common than lateral tear
Mechanism
· twisting force on knee when it is partially flexed (e.g. stepping down and turning)
· requires moderate trauma in young person but only mild trauma in elderly due to degeneration
Clinical Features
· immediate pain, difficulty weight-bearing, instability and clicking
· increased pain with squatting and/or twisting
· effusion (hemarthrosis) with insidious onset (24-48 hrs after injury)
· joint line tenderness medially or laterally
· locking of knee (if portion of meniscus mechanically obstructing extension)
Investigations
· MRI, arthroscopy
Treatment
· if not locked: ROM and strengthening
· if locked or failed above: arthroscopic repair/partial meniscectomy
Quadriceps/Patellar Tendon Rupture
Mechanism
· sudden forceful contraction of quadriceps during an attempt to stop
· more common in obese patients and those with pre-existing degenerative changes in tendon
o DM, SLE, RA, steroid use, renal failure on dialysis
Clinical Features
· inability to extend knee or weight-bear
· possible audible "pop"
· patella in lower or higher position with palpable gap above or below patella respectively
· may have an effusion
Investigations
· ask patient to straight leg raise
· knee x-ray to rule out patellar fracture
· lateral view: patella alta with patella tendon rupture, patella baja with quadriceps tendon rupture
Treatment
· non operative treatment for incomplete tears with preserved extension of knee
· surgical repair of tendon indicated for complete ruptures
Dislocated Knee
Mechanism
· high energy trauma
· by definition, caused by tears of multiple ligaments
Clinical Features
· classified by relation of tibia with respect to femur
o anterior, posterior, lateral, medial, rotary
· knee instability
· effusion
· pain
· ischemic limb
Investigations
· x-rays: AP, lateral, skyline
o associated radiographic findings include tibial plateau fracture dislocations, proximal fibular fractures and avulsion of fibular head
· ankle brachial index (abnormal if less than 0.9)
· arteriogram if abnormal vascular exam
Treatment
· urgent closed reduction
o complicated by interposed soft tissue
· assessment of peroneal nerve, tibial artery; and ligamentous injuries
· repair of associated injuries; also may need decompressive fasciotomy especially if vascular repair undertaken fasciotomy
· knee immobilization x 6-8 weeks
Specific Complications
· high incidence of associated injuries
o popliteal artery tear
o peroneal nerve injury
o capsular tear
· chronic: instability, stiffness, post-traumatic arthritis