Level 2 Evidence: Prospective Cohort Study

  • Naomi Roselaar
  • Niv Marom
  • Robert G. MarxEmail author


In the hierarchy used to classify evidence-based research in medicine, level 2 evidence includes prospective cohort studies. A prospective cohort study includes a research question developed prior to patient enrollment. This research design is particularly useful for assessing patient outcomes following a specific treatment or for assessing a specific patient characteristic. Prospective cohort studies may be susceptible to selection bias and low rates of follow-up. Prospective cohort studies can be either controlled or uncontrolled.


Evidence Prospective Cohort Therapeutic Prognostic Controlled Uncontrolled 


  1. 1.
    Benson K, Hartz A. A comparison of observational studies and randomized, controlled trials. N Engl J Med. 2000;342(25):1878–86.CrossRefGoogle Scholar
  2. 2.
    Blokland D, Thijs KM, Backx FJG, Goedhart EA, Huisstede BMA. No effect of generalized joint hypermobility on injury risk in elite female soccer players: a prospective cohort study. Am J Sports Med. 2017;45(2):286–93. Scholar
  3. 3.
    Bryant DM, Willits K, Hanson BP. Principles of designing a cohort study in orthopaedics. J Bone Joint Surg Ser A. 2009;91:10–4. Scholar
  4. 4.
    Burns PB, Rohrich RJ, Chung KC. The levels of evidence and their role in evidence-based medicine. Plast Reconstr Surg. 2011;128(1):305–10. Scholar
  5. 5.
    Concato J, Shah N, Horwitz RI. Randomized, controlled trials, observational studies, and the hierarchy of research designs. N Engl J Med. 2000;342(25):1887–92. Scholar
  6. 6.
    Hanzlik S, Mahabir RC, Baynosa RC, Khiabani KT. Levels of evidence in research published in The Journal of Bone and Joint Surgery (American Volume) over the last thirty years. J Bone Joint Surg. 2009;91(2):425–8. Scholar
  7. 7.
    Hennekens C, Buring J. Epidemiology in medicine. 1st ed. Boston: Little, Brown; 1987.Google Scholar
  8. 8.
    Hentz R, Meals R, Stern P, Manske P. Levels of evidence and the journal of hand surgery. J Hand Surg Am. 2015;30(5):891–2.CrossRefGoogle Scholar
  9. 9.
    JBJS Inc. Journals level of evidence. The Journal of Bone and Joint Surgery. Published 2015.
  10. 10.
    Kapadia BH, Boylan MR, Elmallah RK, Krebs VE, Paulino CB, Mont MA. Does hemophilia increase the risk of postoperative blood transfusion after lower extremity total joint arthroplasty? J Arthroplast. 2016;31:1578–82. Scholar
  11. 11.
    Koh KH, Ahn JH, Kim SM, Yoo JC. Treatment of biceps tendon lesions in the setting of rotator cuff tears: prospective cohort study of tenotomy versus tenodesis. Am J Sports Med. 2010;38(8):1584–90. Scholar
  12. 12.
    Sedgwick P. Prospective cohort studies: advantages and disadvantages. BMJ. 2013;347:f6726. Scholar
  13. 13.
    Sedgwick P. What is recall bias? BMJ. 2012;344:e3519.CrossRefGoogle Scholar
  14. 14.
    Skolasky RL, Maggard AM, Wegener ST, Riley Iii LH. Telephone-based intervention to improve rehabilitation engagement after spinal stenosis surgery: a prospective lagged controlled trial. J Bone Joint Surg. 2018;100:21–30. Scholar
  15. 15.
    Slobogean G, Bhandari M. Introducing levels of evidence to the journal of orthopaedic trauma: implementation and future directions. J Orthop Traumatol. 2012;26(3):127–8.Google Scholar
  16. 16.
    Song JW, Chung KC. Observational studies: cohort and case-control studies. Plast Reconstr Surg. 2010;126(6):2234–42. Scholar
  17. 17.
    Wright JG, Swiontkowski MF, Heckman JD. Introducing levels of evidence to the journal. J Bone Joint Surg. 2003;85(1):1–3.CrossRefGoogle Scholar

Copyright information

© ISAKOS 2019

Authors and Affiliations

  1. 1.Hospital for Special SurgeryNew YorkUSA

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