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Knee Osteoarthritis

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Other Names

  • Osteoarthritis of the knee
  • Degenerative joint disease (DJD) of the knee
  • Patellofemoral Osteoarthritis
  • Femorotibial Osteoarthritis
  • Knee Arthritis


  • This page refers to osteoarthritis (OA) of the Knee Joint
    • Herein referred to as 'Knee OA'



  • It is estimated that 250 million people all over the world suffer from OA[1]
  • Prevalence of knee OA increased significantly over the last decades, continues to rise[2]
    • Due to obesity and other risk factors, but also independently, of other causes
    • Affects individual ability to walk (22%), lift (18.6%), and dress (12.8%)[3]
  • Prevalence of knee OA among adults 60 years of age or older is approximately 10% in men and 13% in women[4]
  • Approximately 85% of the burden of osteoarthritis worldwide is connected with knee OA[5]
  • Estimated symptomatic knee OA is 240 per 100,000 per year (need citation)
  • Economic burden
    • OA causes an annual economic burden of at least USD 89.1 billion, primarily related to hip and knee replacements[6]
    • Following low-back pain, OA #2 musculoskeletal disorder in Disability Adjusted Life Years (DALYs) in elderly population[7]


  • General
  • Osteoarthritis (Main)
    • Progressive, degenerative condition
    • Result of loss of articular cartilage
    • Typically becomes more severe, frequent, and debilitating over time



  • Knee Joint
    • Largest synovial joint in the body
    • Osseous structures (distal femur, proximal tibia, and patella)
    • Cartilage (meniscus and hyaline cartilage)
    • Ligaments
    • Synovial membrane

Associated Conditions

Risk Factors

  • General
  • Occupational
    • Kneeling[11]
    • Heavy lifting
    • Repetitive knee bending
  • Sports[12]
    • Long-distance running
    • Football
    • Handball
    • Hockey
  • Other knee pathology
    • History of previous knee injuries
    • Joint malalignment
    • Instability
    • Cartilage defects
    • Meniscal injury
    • Anterior cruciate ligament (ACL) tears
  • Other

Differential Diagnosis

Clinical Features

  • History
    • In most cases, there is no history of trauma or knee injury
    • About 5% of patients will have had previous knee injury
    • Pain onset may be slow and insidious
    • Other times sudden standing or twisting motions may precipitate the first flare
    • Pain is often worse with use, better with rest
    • In early knee OA, it may be specific activities that are limited
    • In more advanced stages, most activities of daily living are affected
    • Patients may endorse stiffness, swelling, restricted range of motion
    • Pain after prolonged sitting or standing
  • Physical Exam: Physical Exam Knee
    • Joint deformity is common in advanced stages
    • Tenderness to joint line is common
  • Special Tests



  • Standard Radiographs Knee
    • Need to be weight bearing
    • Consider sunrise view to evaluate patellofemoral joint space
  • Findings
    • Joint space narrowing (medial more common than lateral or patellofemoral)
    • Eburnation of bone
    • Osteophytes
    • Subchondral cysts
    • Subchondral sclerosis


  • No major role for knee OA
  • May be useful in select cases for pre-op planning


  • Not routinely required for knee OA diagnosis
  • Technically more sensitive as it better evaluates the soft tissue structures


  • Gaining popularity
  • Can assess most of the soft tissue structures


Kellgren and Lawrence (KL) Classification

  • Grade 0: no radiographic features of OA present
  • Grade 1: doubtful joint space narrowing, possible osteophytic lipping
  • Grade 2: definite osteophytes, possible joint space narrowing on anteroposterior weight-bearing radiograph
  • Grade 3: multiple osteophytes, definite joint space narrowing, sclerosis, possible bony deformity
  • Grade 4: large osteophytes, marked joint space narrowing, severe sclerosis and definite bony deformity



  • Indications
    • First line treatment in majority of cases
  • Exercise Therapy
    • Can either be land-based or water-based depending on patients needs, function and access
    • Decreased activity: cartilage degeneration, decrease of glycosaminoglycan, impaired joint mechanics and flexibility
    • Light-to-moderate physical activity provides functional and mechanical benefits
    • Strong evidence of benefit: focus on aerobic/cardiovascular conditioning and lower extremity strength training[14]
    • Avoid: high impact activities
    • Goal: long-term adherence should be maximized to increase success
  • Aquatic Therapy
    • Alternative to land based activity with less impact
    • Patients may better tolerate aquatic therapy, decrease the exacerbation of symptoms
    • Can be used as a bridge to get to land-based modalities[15]
  • Weight Loss
    • Obesity: predispose patients to suffer from knee OA, deleterious molecular and mechanical effects
    • Adipocytes source of inflammation (adipokine, IL6, TNF alfa, and C-reactive protein)
    • During ambulation, the knee joint has to support 3–5x the body weight
    • 10% risk reduction of knee OA per kilogram of body-weight decreased[16]
    • The Framingham study: weight loss of 12 lb resulted in a 50% risk reduction for knee OA[17]
    • Reduction in body fat %: 1 point reduction leads 28% increase in function, 9.4% improvement in the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score[18]
  • Medications
    • Acetaminophen
      • Overall safe in patients without hepatic disease
      • Inferior to NSAIDS, some studies have shown non superior to placebo for pain control
    • Oral NSAIDS
    • Topical NSAIDS
      • Safer with comparable or slightly inferior efficacy to systemic NSAIDS for OA[19]
    • Duloxetine
      • At 10 weeks, superior to placebo for pain, function in patients with OA[20]
    • Tramadol
      • Some benefit in the treatment of severe, moderate OA
      • Less risk of abuse, respiratory depression compared to other opioids[21]
    • Opioids
      • Non-superior to NSAIDS for OA pain, WOMAC scores[22]
      • Risks outweight benefits
  • Supplements
  • Corticosteroid Injection
    • Some controversy over efficacy and available data leading to mixed recommendations from societies
    • Identifying appropriate candidates has been challenging
    • Low KL (0-1) related with better response compared to severe changes (3-4)[23]
  • Adductor Canal Block (ACB)
    • Ultrasound guided block which anesthetizes the saphenous nerve
    • Ming et al found it superior to CSI for analgesia, quality of life, function at 3 months[24]
    • Lee et al had positive findings in a retrospective case-control study[25]
    • Salihovic et al found it decreased pain and increased ambulation[26]
  • Viscosupplementation
    • Conflicting evidence over efficacy resulting in mixed recommendations from societies
    • Greatest efficacy may be seen in patients with higher levels of knee pain, younger and with lower KL score[27]
  • Regenerative Medicine
  • Insufficient evidence to recommend


  • Indications
    • Failure of conservative measures
    • Younger patient with unicompartmental OA
  • Technique
    • Total Knee Arthroplasty
    • High Tibial Osteotomy
    • Unicompartmental Arthroplasty

Rehab and Return to Play


  • Needs to be updated

Return to Play

  • Needs to be updated

Complications & Prognosis


  • Non-surgical therapy
    • 81% of patients who do not achieve pain control with pharmacotherapy prefer not to have surgery (need citation)


  • Chronic Pain
  • Need for surgery
  • Impact on activities of daily living
    • Difficulty ambulating, walking
    • Trouble lifting
    • Trouble dressing

See Also


  1. Hunter D.J., Bierma-Zeinstra S. Osteoarthritis. Lancet. 2019;393:1745–1759. doi: 10.1016/S0140-6736(19)30417-9.
  2. Nguyen U.-S.D.T., Zhang Y., Zhu Y., Niu J., Zhang B., Felson D.T. Increasing Prevalence of Knee Pain and Symptomatic Knee Osteoarthritis: Survey and Cohort Data. Ann. Intern. Med. 2011;155:725–732.
  3. Palazzo C, Ravaud JF, Papelard A, Ravaud P, Poiraudeau S. The burden of musculoskeletal conditions. PLoS One 2014; 9: e90633.
  4. Zhang Y., Jordan J.M. Epidemiology of Osteoarthritis. Clin. Geriatr. Med. 2010;26:355–369.
  5. GBD 2015 Disease and Injury Incidence and Prevalence Collaborators Global, regional, and national incidence, prevalence, and years lived with disability for 310 diseases and injuries, 1990–2015: A systematic analysis for the Global Burden of Disease Study 2015. Lancet. 2016;388:1545–1602.
  6. GBD 2015 Disease and Injury Incidence and Prevalence Collaborators Global, regional, and national incidence, prevalence, and years lived with disability for 310 diseases and injuries, 1990–2015: A systematic analysis for the Global Burden of Disease Study 2015. Lancet. 2016;388:1545–1602.
  7. Prince M.J., Wu F., Guo Y., Gutierrez Robledo L.M., O’Donnell M., Sullivan R., Yusuf S. The burden of disease in older people and implications for health policy and practice. Lancet. 2015;385:549–562.
  8. 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.
  9. Kang I, Sang WH. Anserine bursitis in patients with osteoarthritis of the knee. South. Med. J. 2000; 93:207Y9.
  10. Shane Anderson A., Loeser R.F. Why is osteoarthritis an age-related disease? Best Pract. Res. Clin. Rheumatol. 2010;24:15–26.
  11. Harris E.C., Coggon D. HIP osteoarthritis and work. Best Pract. Res. Clin. Rheumatol. 2015;29:462–482.
  12. Driban J.B., Hootman J.M., Sitler M.R., Harris K.P., Cattano N.M. Is Participation in Certain Sports Associated With Knee Osteoarthritis? A Systematic Review. J. Athl. Train. 2017;52:497–506.
  13. Silverwood, V., et al. "Current evidence on risk factors for knee osteoarthritis in older adults: a systematic review and meta-analysis." Osteoarthritis and cartilage 23.4 (2015): 507-515.
  14. Esser S, Bailey A. Effects of exercise and physical activity on knee osteoarthritis. Curr Pain Headache Rep. 2011;15(6):423–430
  15. Tanaka R, Ozawa J, Kito N, Moriyama H. Efficacy of strengthening or aerobic exercise on pain relief in people with knee osteoarthritis: a systematic review and meta-analysis of randomized controlled trials. Clin Rehabil. 2013;27(12):1059–1071.
  16. Messier SP, Gutekunst DJ, Davis C, Devita P. Weight loss reduces knee-joint loads in overweight and obese older adults with knee osteoarthritis. Arthritis Rheum. 2005;52(7):2026–2032.
  17. Felson DT, Zhang Y, Anthony JM, Naimark A, Anderson JJ. Weight loss reduces the risk for symptomatic knee osteoarthritis in women. The Framingham Study. Ann Intern Med. 1992;116(7):535–539
  18. Christensen R, Astrup A, Bliddal H. Weight loss: the treatment of choice for knee osteoarthritis? A randomized trial. Osteoarthritis Cartilage. 2005;13(1):20–27
  19. Lin J, Zhang W, Jones A, Doherty M. Efficacy of topical non-steroidal anti-inflammatory drugs in the treatment of osteoarthritis: meta-analysis of randomised controlled trials. BMJ. 2004;329(7461):324.
  20. Wang ZY, Shi SY, Li SJ, et al. Efficacy and Safety of Duloxetine on Osteoarthritis Knee Pain: A Meta-Analysis of Randomized Controlled Trials. Pain Med. 2015;16(7):1373–1385.
  21. Cepeda MS, Camargo F, Zea C, Valencia L. Tramadol for osteoarthritis: a systematic review and metaanalysis. J Rheumatol. 2007;34(3):543–555.
  22. rebs EE, Gravely A, Nugent S, et al. Effect of Opioid vs Nonopioid Medications on Pain-Related Function in Patients With Chronic Back Pain or Hip or Knee Osteoarthritis Pain: The SPACE Randomized Clinical Trial. JAMA. 2018;319(9):872–882.
  23. Arden NK, Reading IC, Jordan KM, et al. A randomised controlled trial of tidal irrigation vs corticosteroid injection in knee osteoarthritis: the KIVIS Study. Osteoarthritis Cartilage. 2008;16(6):733–739
  24. Ming, Lee Hwee, et al. "Adductor canal block versus intra-articular steroid and lidocaine injection for knee osteoarthritis: a randomized controlled study." The Korean Journal of Pain 35.2 (2022): 191-201.
  25. Lee DH, Lee MY, Kwack KS, Yoon SH. Effect of adductor canal block on medial compartment knee pain in patients with knee osteoarthritis: Retrospective comparative study. Medicine (Baltimore). 2017;96(12):e6374. doi:10.1097/MD.0000000000006374
  26. Salihovic, Mensur, et al. "Effectiveness of Ultrasound-Guided Canal Adductor Blockade for Chronic Pain and Functioning in Knee Osteoarthritis: A Prospective Longitudinal Observational Study." BioMed Research International 2022 (2022).
  27. Pelletier JP, Raynauld JP, Abram F, Dorais M, Delorme P, Martel-Pelletier J. Exploring determinants predicting response to intra-articular hyaluronic acid treatment in symptomatic knee osteoarthritis: 9-year follow-up data from the Osteoarthritis Initiative. Arthritis Res Ther. 2018;20(1):40.
  28. Shahid M, Kundra R. Platelet-rich plasma (PRP) for knee disorders. EFORT Open Rev. 2017;2(1):28–34.
Created by:
John Kiel on 7 July 2019 05:42:40
Last edited:
25 January 2024 20:08:26