The (Bee’s) Knees!

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Knee pain

  • Affects approx 25% of adults
  • ~4 million primary care visits annually
  • Initial eval: urgent causes, consider referral
  • Hx: age, location, onset, duration, and quality of pain
    • Mechanical or systemic symptoms
    • Hx of swelling or trauma, PMHx, PSHx
  • Urgent Referral: acute trauma OR infection
  • Consider fracture if patient is unable to walk/limp at least 4 steps right after injury and at first presentation
  • Ottawa Knee Rule – determines which acute knee injuries require imaging
  • Clinical pearl: There is a fourfold reduction in force exerted on the knees with each pound of weight loss!

Exam

  • Inspection (look for erythema, discoloration, swelling, bruising, deformities, asymmetry, lacerations, etc)
  • Palpation (look for pain, warmth, effusion, etc)
  • ROM 
    • Normal: extension from 0 to -10° and flexion to 135°
    • Normal patellofemoral tracing vs lateral tracking (J sign)
  • Strength – Graded 0 to 5 for flexion/extension
  • Neurovascular Testing
    • Sensation to light touch
    • Reflexes – Patellar, Achilles
    • Pulses – Popliteal, dorsalis pedis, posterior tibial
  • Curious how to perform a telemedicine exam of the knee? Check out this article by the Mayo Clinic!

Lachman test for ACL tear

  1. Supine
  2. Externally rotate leg
  3. Flex knee to 20-30°
  4. Stabilize femur with one hand
  5. Apply pressure to back of knee
    with other hand with thumb on joint line

POSITIVE – movement of knee with a soft or mushy end point

Anterior drawer test for ACL tear

  1. Supine
  2. Flex hip to 45°
  3. Flex knee to 90°
  4. Sit on dorsum of foot
  5. Wrap hands around proximal hamstrings
  6. Pull and push to assess anterior
    displacement of tibia
  7. Repeat with tibia in neutral position,
    30° externally rotated, 30° internally rotated

POSITIVE – laxity greater than the normal of 6-8 mm

Posterior drawer test for PCL tear

  1. Supine
  2. Flex knee to 90°
  3. Look for posterior displacement of tibia 
    1. Posterior “sag” sign
  4. Sit on dorsum of foot
  5. Position thumbs at tibial tubercles
  6. Position fingers at posterior calf
  7. Push and pull to assess posterior
    displacement of tibia

McMurray Test for Meniscus Tear

  • Flex hip and knee maximally
  • For medial meniscus:
    1. Apply valgus (abduction) force
    2. Externally rotate foot
    3. Passive extension of the knee
  • For lateral meniscus:
    1. Apply varus (adduction) force
    2. Internally rotate foot
    3. Passive extension of the knee

POSITIVE – audible or palpable snap or click with pain during extension

Thessaly Test for Meniscus Tear

  1. Stand flat footed on the floor
  2. Hold patient’s outstretched hands while they stand
  3. Internally and externally rotate affected leg
    3x with knee flexed at 20°
  4. Flexed unaffected leg so it does not touch the floor

POSITIVE – pain reported at medial or lateral join line

Varus Stress & Valgus Stress Tests for Collateral Ligaments

  • Valgus stress to knee at both extension and at 30° flexion → MCL
  • Varus stress to knee at both extension and 30° flexion → LCL

POSITIVE – asymmetric gapping or laxity suggestive of injury

Ballottement Test for Effusion

  1. Supine
  2. Extend injured knee
  3. Push patella posteriorly with 2-3 fingers
    using quick, sharp motion

POSITIVE – if large effusion, patella descends to trochlea, strikes it, and flows back to its former position

DDx for Knee Pain

MECHANICAL (ACUTE)

  • Collateral ligament sprain/rupture
  • Cruciate ligament sprain/rupture
  • Medial plica syndrome
  • Meniscal tear
  • Patellar subluxation/dislocation

INFLAMMATORY

  • Crystal-induced arthropathy

INFECTIOUS

  • Septic joint

MECHANICAL (CHRONIC)

  • Distal patellar apophysitis
  • Iliotibial band syndrome
  • Meniscal derangement or tear
  • Osteoarthritis
  • Patellofemoral pain syndrome
  • Pes anserine bursitis
  • Quadriceps or patellar tendinopathy
  • Tibial apophysitis (Osgood-Schlatter Dz)

Further Reading!

  • Bunt, Christopher W., et al. “Knee Pain in Adults and Adolescents: The Initial Evaluation.” American Family Physician, 1 Nov. 2018
  • Dixit, Sameer, et al. “Management of Patellofemoral Pain Syndrome.” American Family Physician, 15 Jan. 2007
  • Fox, Alice J S, et al. “The Basic Science of Human Knee Menisci: Structure, Composition, and Function.” Sports Health, SAGE Publications, July 2012
  • Logterman, Stephanie L, et al. “Posterior Cruciate Ligament: Anatomy and Biomechanics.” Current Reviews in Musculoskeletal Medicine, Springer US, Sept. 2018
  • Manske, Robert C, and Daniel Prohaska. “Physical Examination and Imaging of the Acute Multiple Ligament Knee Injury.” North American Journal of Sports Physical Therapy: NAJSPT, Sports Physical Therapy Section, APTA, Nov. 2008
  • Petersen, W, and B Tillmann. “[Anatomy and Function of the Anterior Cruciate Ligament].” Orthopade, U.S. National Library of Medicine, Aug. 2002
  • Do bees even have knees?

Blog post based on Med-Peds Forum talk by Ashley Nguyen, PGY2

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