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Knee Pain
Jeff Wang, MD, MPH
J. Herbert Stevenson, MD
image BASICS
DESCRIPTION
Knee pain is a common outpatient complaint with a broad differential diagnosis.
  • Knee pain may be acute, chronic, or an acute exacerbation of a chronic condition.
  • Trauma, overuse, and degenerative change are frequent causes.
  • A detailed history, including patient age, pain onset and location, mechanism of injury, and associated symptoms can help narrow the differential diagnosis.
  • A thorough and focused examination of the knee (as well as the back, hips, and ankles) helps to establish the correct diagnosis and appropriate treatment.
EPIDEMIOLOGY
Incidence
  • Knee pain accounts for 1.9 million primary care visits annually.
  • The incidence of knee osteoarthritis is 240 cases/100,000 person/year.
Prevalence
  • The knee is a common site of lower extremity injury.
    • Patellar tendonopathy and patellofemoral syndrome are the most common causes of knee pain in runners (1).
  • Osteoarthritis (OA) is one of the leading causes of disability in the United States.
ETIOLOGY AND PATHOPHYSIOLOGY
  • Trauma (ligament or meniscal injury, fracture, dislocation)
  • Overuse (tendinopathy, patellofemoral syndrome, bursitis, apophysitis)
  • Age-related (arthritis, degenerative conditions, apophysitis [young])
  • Rheumatologic (rheumatoid arthritis [RA], gout, pseudogout)
  • Infectious (bacterial, postviral, Lyme disease)
  • Referred pain (hip, back)
  • Vascular: popliteal artery aneurysm, deep vein thrombosis
  • Others: tumor, cyst, plica
RISK FACTORS
  • Obesity
  • Malalignment
  • Poor flexibility, muscle imbalance, or weakness
  • Rapid increases in training frequency and intensity
  • Improper footwear, training surfaces, technique
  • Activities that involve cutting, jumping, pivoting, deceleration, kneeling
  • Previous injuries
GENERAL PREVENTION
  • Maintain normal body mass index.
  • Use appropriate exercise training principles; avoid overtraining.
  • Correct postural strength and flexibility imbalances.
  • Proper activity-specific techniques and equipment
COMMONLY ASSOCIATED CONDITIONS
  • Fracture, contusion
  • Effusion, hemarthrosis
  • Patellar dislocation/subluxation
  • Meniscal or ligamentous injury
  • Tendinopathy, bursitis
  • Osteochondral injury
  • OA, septic arthritis
  • Muscle strain
image DIAGNOSIS
PHYSICAL EXAM
  • Observe gait (antalgia), patellar tracking.
  • Inspect for malalignment, atrophy, swelling, ecchymosis, or erythema.
  • Palpate for effusion, warmth, and tenderness.
  • Evaluate active and passive range of motion (ROM) and flexibility of quadriceps and hamstrings.
  • Evaluate strength and muscle tone.
  • Note joint instability, locking, and catching.
  • Evaluate hip ROM, strength, and stability.
  • Special tests:
    • Patellar apprehension test: patellar instability. Patellar grind test: patellofemoral pain or OA (1)
    • Lachman test (more sensitive and specific), pivot shift, anterior drawer: ACL integrity
    • Posterior drawer, posterior sag sign: PCL integrity
    • Valgus/varus stress test: medial/lateral collateral ligament (MCL/LCL) integrity
    • McMurray test, Apley grind, Thessaly test: meniscal injury
    • Ober test: Iliotibial band (ITB) tightness
    • Dial test: positive with posterolateral corner laxity
    • Patellar tilt test and squatting may help suggest patellofemoral pain syndrome, but there is not yet one definitive test.
    • Patella facet tenderness suggests OA or patellofemoral pain syndrome (1)[A].
DIFFERENTIAL DIAGNOSIS
  • Acute onset: fracture, contusion, cruciate or collateral ligament tear, meniscal tear, patellar dislocation/subluxation. If systemic symptoms: septic arthritis, gout, pseudogout, Lyme disease, and osteomyelitis
  • Insidious onset: patellofemoral pain syndrome/chondromalacia, ITB syndrome, OA, RA, bursitis, tumor, tendinopathy, loose body, bipartite patella, degenerative meniscal tear
  • Anterior pain: patellofemoral pain syndrome, patellar injury, patellar tendinopathy, pre- or suprapatellar bursitis, tibial apophysitis, fat pad impingement, quadriceps tendinopathy, OA (1)
  • Posterior pain: PCL injury, posterior horn meniscal injury, popliteal cyst or aneurysm, hamstring or gastrocnemius injury, deep venous thrombosis (DVT)
  • Medial pain: MCL injury, medial meniscal injury, pes anserine bursitis, medial plica syndrome, OA
  • Lateral pain: LCL injury, lateral meniscal injury, ITB syndrome, OA
DIAGNOSTIC TESTS & INTERPRETATION
Initial Tests (lab, imaging)
  • Suspected septic joint, gout, pseudogout:
    • Arthrocentesis with cell count, Gram stain, culture, protein/glucose, synovial fluid analysis
  • Suspected RA:
    • CBC, erythrocyte sedimentation rate (ESR), rheumatoid factor
  • Consider Lyme titer.
  • Radiographs to rule out fracture in patients with acute knee trauma (Ottawa rules):
    • Age >55 years or
    • Tenderness at the patella or fibular head or
    • Inability to bear weight 4 steps or
    • Inability to flex knee to 90 degrees
  • Radiographs help diagnose OA, osteochondral lesions, patellofemoral pain syndrome:
    • Weightbearing, upright anteroposterior, lateral, merchant/sunrise, notch/tunnel views
Follow-Up Tests & Special Considerations
  • MRI is a “gold standard” for soft tissue imaging.
  • Ultrasound may help diagnose tendonopathy (2)[B].
  • CT can further elucidate fracture.
Diagnostic Procedures/Other
Arthroscopy may be beneficial in the diagnosis of certain conditions, including meniscus and ligament injuries.
Geriatric Considerations
OA, degenerative meniscal tears, and gout are more common in middle-aged and elderly populations.
Pediatric Considerations
  • 3 million pediatric sports injuries occur annually.
  • Look for physeal/apophyseal and joint surface injuries in skeletally immature:
    • Acute: patellar subluxation, avulsion fractures, ACL tear
    • Overuse: patellofemoral pain syndrome, apophysitis, osteochondritis dissecans, patellar tendonitis, stress fracture
    • Others: neoplasm, juvenile RA, infection, referred pain from slipped capital femoral epiphysis
P.583

image TREATMENT
GENERAL MEASURES
Acute injury: PRICEMM therapy (protection, relative rest, ice, compression, elevation, medications, modalities)
MEDICATION
First Line
  • Oral medications:
    • Acetaminophen: up to 3 g/day. Safe and effective in OA
    • Nonsteroidal anti-inflammatory drugs (NSAIDs):
      • Ibuprofen: 200 to 800 mg TID
      • Naproxen: 250 to 500 mg BID:
        • Useful for acute sprains, strains
        • Useful for short-term pain reduction in OA. Long-term use is not recommended due to side effects.
        • Not recommended for fracture, stress fracture, chronic muscle injury; may be associated with delayed healing; low dose and brief course only if necessary
    • Tramadol/opioids: not recommended as first-line treatment; can be used with acute injuries
    • Celecoxib: 200 mg QID may be effective in OA with less GI side effects than NSAIDs (3)[A].
  • Topical medications:
    • Topical NSAIDs may provide pain relief in OA and are more tolerable than oral medications.
    • Topical capsaicin may be an adjuvant for pain management in OA.
  • Injections:
    • Intra-articular corticosteroid injection may provide short-term benefit in knee OA (2)[A].
    • Viscosupplementation may reduce pain and improve function in patients with OA (2)[A], particularly those wishing to delay joint replacement.
ISSUES FOR REFERRAL
  • Acute trauma, young athletic patient
  • Joint instability
  • Lack of improvement with conservative measures
  • Salter-Harris physeal fractures (pediatrics)
ADDITIONAL THERAPIES
  • Physical therapy is recommended as initial treatment for patellofemoral pain (4) and tendonopathies (2)[A].
  • Muscle strengthening improves outcome in OA.
  • Foot orthoses, taping, acupuncture
  • May need bracing for stability (4)
  • Plate-rich plasma injection in early OA (5)[B]
  • Botulinum toxin A for patellofemoral pain syndrome (6)[B]
SURGERY/OTHER PROCEDURES
  • Surgery may be indicated for certain injuries (e.g., ACL tear in competitive athletes).
  • Chronic conditions refractory to conservative therapy may require surgical intervention.
COMPLEMENTARY & ALTERNATIVE MEDICINE
May reduce pain and improve function in early OA:
  • Glucosamine sulfate (500 mg TID) (7)
  • Chondroitin (400 mg TID) (7)
  • S-adenosylmethionine (SAMe), ginger extract, methylsulfonylmethane: less reliable improvement with inconsistent supporting evidence (8)
  • Acupuncture
image ONGOING CARE
FOLLOW-UP RECOMMENDATIONS
  • Activity modification in overuse conditions
  • Rehabilitative exercise in OA:
    • Low-impact exercise: walking, swimming, cycling
    • Strength, ROM, and proprioception training
Patient Monitoring
  • Rehabilitation after initial treatment of acute injury.
  • In chronic and overuse conditions, assess functional status, rehabilitation adherence, and pain control at follow-up visit.
DIET
Weight reduction for overweight patient with OA
PATIENT EDUCATION
  • Review activity modifications.
  • Encourage active role in the rehabilitation process.
  • Review medication risks and benefits.
PROGNOSIS
Varies with diagnosis, injury severity, chronicity of condition, patient motivation to participate in rehabilitation, and whether surgery is required
REFERENCES
1. Hong E, Kraft MC. Evaluating anterior knee pain. Med Clin North Am. 2014;98(4):697-717.
2. Ayhan E, Kesmezacar H, Akgun I. Intraarticular injections (corticosteroid, hyaluronic acid, platelet rich plasma) for the knee osteoarthritis. World J Orthop. 2014;5(3):351-361.
3. Bijlsma JW, Berenbaum F, Lafeber FP. Osteoarthritis: an update with relevance for clinical practice. Lancet. 2011;377(9783):2115-2126.
4. Bolgla LA, Boling MC. An update for the conservative management of patellofemoral pain syndrome: a systematic review of the literature from 2000 to 2010. Int J Sports Phys Ther. 2011;6(2):112-125.
5. Campbell KA, Saltzman BM, Mascarenhas R, et al. Does intra-articular platelet-rich plasma injection provide clinically superior outcomes compared with other therapies in the treatment of knee osteoarthritis? A systematic review of overlapping meta-analyses. Arthroscopy. 2015;31(11):2213-2221.
6. Chen JT, Tang AC, Lin SC, et al. Anterior knee pain caused by patellofemoral pain syndrome can be relieved by Botulinum toxin type A injection. Clin Neurol Neurosurg. 2015;129(Suppl 1):S27-S29.
7. Henrotin Y, Marty M, Mobasheri A. What is the current status of chondroitin sulfate and glucosamine for the treatment of knee osteoarthritis? Maturitas. 2014;78(3)184-187.
8. Debbi EM, Agar G, Fichman G, et al. Efficacy of methylsulfonylmethane supplementation on osteoarthritis of the knee: a randomized controlled study. BMC Complement Altern Med. 2011;11:50.
Additional Reading
&NA;
  • Collins NJ, Bisset LM, Crossley KM, et al. Efficacy of nonsurgical interventions for anterior knee pain: systematic review and meta-analysis of randomized trials. Sports Med. 2012;42(1):31-49.
  • Derry S, Moore RA, Rabbie R. Topical NSAIDs for chronic musculoskeletal pain in adults. Cochrane Database Syst Rev. 2012;(9):CD007400.
  • Lopes AD, Hespanhol Júnior LC, Yeung SS, et al. What are the main running-related musculoskeletal injuries? A systematic review. Sports Med. 2012;42(10):891-905.
  • Nunes GS, Stapait EL, Kirsten MH, et al. Clinical test for diagnosis of patellofemoral pain syndrome: systematic review with meta-analysis. Phys Ther Sport. 2013;14(1):54-59.
  • Ziltener JL, Leal S, Fournier PE. Non-steroidal antiinflammatory drugs for athletes: an update. Ann Phys Rehabil Med. 2010;53(4):278-282.
See Also
&NA;
Algorithms: Knee Pain; Popliteal Mass
Codes
&NA;
ICD10
  • M25.569 Pain in unspecified knee
  • M17.9 Osteoarthritis of knee, unspecified
  • M76.50 Patellar tendinitis, unspecified knee
Clinical Pearls
&NA;
  • Consider ligamentous injury, meniscal tear, and fracture for patients presenting with acute knee pain.
  • Consider OA, patellofemoral pain, syndrome, tendinopathy, bursitis, and stress fracture in patients presenting with more chronic symptoms.
  • Consider physeal, apophyseal, or articular cartilage injury in young patients presenting with knee pain.
  • The presence of an effusion in a patient <30 years of age indicates a significant injury.
  • Referred pain from the hip (slipped capital femoral epiphysis, Legg-Calvé-Perthes disease) can present as knee pain.