Orthopaedics: Knee

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