How Common Is TKA in Individuals Under Age 21, and Why Is It Performed?

Total knee arthroplasty (TKA) is rarely performed in patients under 21 years old but may be done in this population due to conditions such as inflammatory arthritis or juvenile idiopathic arthritis (JIA), malignant or non-malignant tumors, or trauma. However, the number of patients under the age of 21 undergoing TKA in the US is unknown.

To bring some clarity to issues surrounding TKA in this very young population, researchers from Hospital for Special Surgery retrospectively analyzed data from the Kids’ Inpatient Database (KID), a national weighted sample of all inpatient hospital admissions of patients under 21 years old in approximately 4200 hospitals in 46 states.

Their findings were presented at the recent American College of Rheumatology Convergence 2022 meeting.

Study Methods and Findings

The researchers used International Classification of Diseases (ICD-9 and ICD-10) codes to identify patients who underwent TKA between 2000 and 2016 and to determine the primary diagnosis. Descriptive statistics such as means and percentages, along with their 95% confidence intervals (95% CI), were calculated using the appropriate sample weights as recommended by the Agency for Healthcare Research and Quality for use with the KID dataset.

The total weighted number of TKAs performed from 2000 to 2016 in patients younger than age 21 was 1331, with the number of TKAs performed in this age group annually remaining relatively stable.

The researchers further found that:

  • The mean age of patients undergoing TKA was 14.8 years (95% CI, 14.4-15.2)
  • 51.2% of the cohort was male and 48.8% was female
  • Most TKAs in this young population were performed in urban teaching hospitals and in facilities with a large number of beds
  • 70.3% of TKAs were performed for a primary diagnosis of a tumor, with the number of malignant tumors increasing slightly over the study period
  • Use of TKA for inflammatory arthritis/JIA decreased by more than 70% over the study period, likely due to improvements in medical management of inflammatory arthritis/ JIA patients

“This was one of the first studies to take an in-depth look at TKA in this very young population,” said Cynthia A. Kahlenberg, MD, MPH, a study co-author and an orthopaedic surgeon at HSS. “Our study was able to confirm that tumors were the most common reason for knee arthroplasty in [these patients].”


Gibbons J, Kahlenberg CA, Jannat-Khah D, Christ AB, Goodman S, Sculco P, Figgie M, Mehta B. A United States Nationwide Analysis of Total Knee Arthroplasty in Patients < 21 Years Old (Abstract 08780). Presented at the American College of Rheumatology Convergence 2022, November 10-14, 2022, in Philadelphia, Pennsylvania.

Leave a Reply

CME Updates