Knee Pain

Samuel Lazaroff

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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 

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Last update: 2022-06-24 16:50:31