Knee Pain

Initial Considerations and Knee Exam

Red Flags

• Acute trauma associated with

  • Severe pain, swelling, and/or instability

  • Inability to bear weight after the event

• Signs of joint infection including

  • Fever, swelling, and overlying erythema

  • Limited range of motion

Physical Exam Maneuvers

• Patellar apprehension test

• Posterior drawer test

• Lachman maneuver

• Anterior drawer test

• Lateral pivot-shift test

• Thessaly maneuver

• McMurray test

Imaging

• Refer for imaging after acute trauma if the patient meets one of the following criteria (Ottawa Knee Rules):

  • Age ≥ 55

  • Isolated patella tenderness

  • Tenderness at fibular head

  • Unable to flex knee to 90 degrees

  • Unable to walk ≥ 4 steps

• Consider imaging in cases of chronic knee pain (i.e. > 6 weeks) after failure of conservative management

Diagnosis

Etiology per Mechanism and Pain Location

Trauma

• Anterior knee pain: Patellar subluxation/dislocation

  • Adolescent with lateral patellar dislocation when the knee is held in 30 degrees of flexion, patellar effusion, and a positive apprehension test.

  • Reduction performed with the hip in flexion as lateral pressure is applied to the patella while the knee is extended. If unsuccessful, refer to orthopedics.

• Posterior knee pain: Posterior cruciate ligament (PCL) injury

  • PCL prevents posterior displacement of tibia.

  • PCL injury: Blunt trauma to anterior tibia with knee in flexion (e.g. dashboard injury) resulting in pain with kneeling. Positive posterior “sag” sign and/or posterior drawer test. Obtain plain radiograph per Ottawa knee rules +/- MRI. Refer to orthopedics for ligament insertion avulsion and/or ≥ Grade 3 injury.

• Mediolateral

  • ACL (anterior cruciate ligament) injury: Sudden deceleration or change in direction resulting in audible “pop” and knee pain, effusion, and instability. Perform Lachman, anterior drawer, and lateral pivot-shift test. Obtain MRI and refer to orthopedics.

  • MCL (medial collateral ligament) sprain/rupture: Injury due to valgus force with asymmetric gapping or laxity.

  • Meniscal injury: Patient age > 40 years with s/p twisting injury with knee locking and/or instability. Medial joint line tenderness and positive

    • Thessaly maneuver (most accurate physical maneuver)

    • McMurray test: Click or pain when moving knee from flexion to extension with valgus stress

Overuse Injury

• Anterior knee pain: Avoid MRI until s/p 6 weeks of physical therapy

  • Patellofemoral pain syndrome: More common in women. Worse after prolonged sitting or when walking down stairs/hills. No associated knee effusion and positive patellar grind test.

  • Patellar tendinitis (Jumper’s Knee): Adolescent athlete involved in jumping sports who endorses infrapatellar pain with palpation of the patellar tendon, e.g. while evaluating patellar reflexes.

• Mediolateral: Iliotibial band syndrome presenting with lateral knee pain in patients with h/o repetitive flexion (e.g. runners, cyclists). Pain present along the iliotibial band on exam.

Swelling/Effusion

• Anterior/Anteromedial

  • Prepatellar bursitis: Anterior, unilateral knee swelling without fever, joint erythema. Initiate conservative management and consider joint aspiration.

  • Pes anserine bursitis: Tender nodule overlying the anteromedial tibia.

• Posterior: Baker’s cyst (obtain ultrasound if suspected)

• Diffuse Inflammatory Arthropathy

  • Unilateral or bilateral

    • Knee osteoarthritis: Age > 50 years with diffuse pain worse when initiating movement and with prolonged activity/weightbearing. Crepitus on exam; swelling/effusion may not be present.

    • Rheumatoid arthritis

  • Unilateral

    • Crystal arthropathy: Gout vs. pseudogout

    • Septic arthritis: Presenting with joint erythema, warmth, and immobility. Elevated WBC, ESR, CRP. Obtain immediate arthrocentesis with gram stain and culture if suspected.

Adolescents

• Anterior knee pain

  • Osgood-Schlatter disease (tibial apophysitis): Age 10 to 15 years. Generally associated with a growth-spurt. Atraumatic knee pain at tibial tubercle.

  • Infrapatellar pain in adolescents: See Overuse injuries above

    • Patellofemoral syndrome

    • Patellar tendinitis (Jumper’s Knee)

• Referred pain: Slipped Capital Femoral Epiphysis (SCFE)

  • More commonly associated with hip pain in an obese patient

  • Obtain plain radiographs and refer to orthopedics if confirmed as risk for avascular necrosis is 30% if not appropriately treated