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Knee Pain

Samuel Lazaroff

Background

  • Key features of the history include:

    • Location: have patient point to the area that hurts most

    • Weight bearing, systemic symptoms (e.g. fevers)

    • Trauma and mechanism of injury

      • High-energy trauma: high risk of bony and/or ligamentous injury

      • Low-Energy Trauma and Atraumatic etiologies organized by location (see table)

    • Presence/absence of effusion and swelling

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:

    • DDx: 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

  • PT 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