Knee Pain

Knee Pain – Samuel Lazaroff

Background

  • Key features of the history include location: have patient point to the area that hurts most
  • Septic arthritis can also present indolently, with well-appearing, afebrile, patients
  • History of trauma, swelling, systemic symptoms, weight-bearing 
  • Consider mechanism of injury à presence/absence of effusion à location 
    • High-energy trauma:  high risk of bony and/or ligamentous injury
    • Low-Energy Trauma and Atraumatic etiologies organized by location

 

Knee Location 

Low-Energy Trauma

Atraumatic

Anterior 

  • Patellar subluxation or dislocation (instability) 
  • Patellar fracture 
  • Patellar tendon rupture 
  • Quadriceps tendon rupture 
  • Tendinopathy: patellar or quadricep
  • Hoffa’s fat pad syndrome (inflammation of post-patellar fat) 
  • Bursitis  
  • OA 

Medial 

  • MCL tear 
  • Acute medial meniscus tear 
  • Medial meniscus degenerative tear 
  • Pes anserine bursitis 
  • OA 

Lateral 

  • LCL tear 
  • Acute lateral meniscus tear 
  • IT band syndrome 
  • Lateral meniscus degenerative tear 
  • OA 

Posterior 

  • PCL tear 
  • Hyperextension 
  • Baker’s cyst 
  • Popliteal art. aneurysm/entrapment 

Generalized 

  • ACL tear 
  • PCL tear 
  • Intra-articular fracture 
  • Patellofemoral pain syndrome 
  • OA 
  • Patellar stress fracture 
  • Referred from hip or ankle 

 

Presentation

  • Traumatic Effusion:
    • Differential is ACL or PCL rupture, meniscus tear, patellar instability (dislocation of subluxation), bone bruise, fracture 
  • Atraumatic Effusion:  
    • Activity related or pain w/activity: Osteoarthritis, Osteochondral injury
  • Not activity-related: Consider autoimmune causes, crystalline arthropathy, Lyme disease, Septic arthropathy (including gonococcal) 
  • Less common causes: primary bone tumor, viral infection (Parvo), hyperparathyroidism, hemochromatosis, syphilis, sarcoid, Whipple’s 

 

Evaluation

  • Physical Exam: 
    • Inspection, palpation, AROM, PROM, strength, check for effusion, neurovascular exam (incl. reflexes if applicable), provocation (of ligaments), gait
    • Examine the back, hip, and ankle as well
  • Aspirate if effusion present
  • Ottawa Knee Rule = Imaging if 1 of following: 
    • > 55 y/o 
    • Isolated tenderness of patella 
    • Tenderness of fibular head 
    • Unable to flex 90° º
    • Unable to ambulate 4 steps at time of injury and at time of evaluation 

Provocation Tests of the Knee 

Test

Isolates

Action

Positive if

Anterior Drawer

ACL 

Hip flexed and knee in 90° of flexion, pull anteriorly on tibia 

Tibia translates forward 

Pivot Shift

ACL 

With knee extended, internally rotate the foot and apply valgus force 

Translation of femur

or tibia 

Lachman 

ACL 

With knee flexed 20°, hold thigh down with one hand while pulling anteriorly on tibia with your other hand (with thumb on tibial joint line) 

Soft end point of tibial translation 

Posterior drawer 

PCL 

With hip flexed and knee in 90° of flexion, push posteriorly on tibia 

Tibia translates backwards 

Joint line tenderness  

Meniscus 

Palpate 

Reproduces pain at site 

McMurray

Meniscus 

With hip & knee flexed, apply: 

  • Medial: valgus force and internal rotate foot 
  • Lateral: varus force and externally rotate foot 

Click, pop, or reproduces pain 

Noble Compression 

IT band 

Patient lies on unaffected side, flex knee while pressure applied to distal IT band (lateral epicondyle) 

Click, pop, or reproduces pain 

Patellar compression 

Patello-femoral pain 

With knee extended and quads relaxed, apply direct pressure to anterior patella as patient tightens quads 

Reproduces pain 

Patellar apprehension

Patello-femoral pain 

With knee flexed to 30°, displace patella laterally 

Patient grimaces or tries to straighten leg 

Imaging

  • X-ray: b/l AP, unilateral, lateral, b/l sunrise view
  • Obtain X-rays in standing position (or joint space narrowing may not be apparent) 
  • MSK U/S: allows for dynamic imaging and is ≈100% sensitive for effusion 
  • Also visualizes ligaments, muscles/tendons, joint space, and vasculature 
  • MRI:  indicated after failure of conservative management or when considering surgical repair 

Treatment: 

  • RICE (rest, ice, compression, elevation) for acute injuries 
  • Bracing 
  • NSAIDs: see prior section for anti-inflammatory dosing
  • Physical therapy for 4-6 weeks for ligamentous, muscular, or meniscal injury  
  • Antibiotics may be appropriate for bursitis if infection is suspected 
  • Referral to orthopedics/sports medicine if no improvement after conservative therapy
    • Surgery reserved for young, athletic people with ligamentous injury