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Patients age 55 and younger were found to have worse pain, function, and quality of life following total knee arthroplasty (TKA) compared with patients age 75 years and older, according to a study presented at the 2023 annual meeting of the American Academy of Orthopaedic Surgeons.

Total knee arthroplasty is one of the most performed surgical procedures in the US, with the number of procedures expected to reach 7.4 million by 2030. While the mean age for patients undergoing TKA is 67.2 years, younger and more-active patients are undergoing TKA.

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“There was controversy in the existing literature examining knee replacement outcomes by age, as some studies concluded young patients do better, other studies showed they do worse, and then there were studies saying there was no difference based on age,” said lead author David Ayers, MD, FAAOS, orthopaedic surgeon, University of Massachusetts Chan Medical School.

“These studies included relatively small sample sizes and different types of methodologies, so we wanted to improve upon our base knowledge by analyzing a large data sample.”

Study Methodology

The researchers used data from the Function and Outcomes Research for Comparative Effectiveness in Total Joint Replacement (FORCE-TJR) consortium, which is managed by Dr. Ayers at the University of Massachusetts Department of Orthopedics and Physical Rehabilitation. This consortium includes more than 235 surgeons from hospitals across the country, providing a representative sample of national data.

The study, “Age-Related Differences in Pain, Function and Quality of Life Following Primary Total Knee Arthroplasty,” analyzed 11,602 patients who underwent a unilateral TKA, with patients segmented into cohorts by ages: under 55, 55-64, 65-74 and 75 and older.

The following patient data were collected prior to surgery and at 1 year postoperative:

• Demographics
• Comorbidity conditions using the Charleson Comorbidity Index
• Patient-reported outcome measures (PROMs), including Knee Injury and Osteoarthritis Outcomes Scores (KOOSs) to determine their levels of pain, function, and quality of life
• Short-form health survey (SF-12), which provided a Physical Composite Score and Mental Composite Score to assess the overall physical, social, and emotional status of the patient

Study Findings

The study authors found that prior to surgery, younger patients (55 and younger) reported worse pain, function, and quality of life compared with older patients, especially those 75 and older. At 1 year after TKA, younger patients still reported slightly worse pain, function, and quality of life, but better function scores than patients older than 75.

“There’s a misnomer that patients under 55 who need a knee replacement are athletes or physically active individuals who have been exercising all their life but had a previous injury which caused osteoarthritis,” Dr. Ayers said.

“Instead, we found that overall, this group had a higher incidence of obesity (BMI>35) and medical comorbidities and were more likely to be current smokers. These factors and any previous injuries to the knee can result in arthritis, which can be significant enough to lead to TKA.”

All Age Groups Benefit

Despite the difference in pain and quality-of-life scores among the age groups, the study showed that all 4 age groups greatly benefited from TKA, experiencing major improvements in pain, function, and quality of life.

“Because of the successful nature of TKAs and with improved anesthetic techniques and rapid recovery protocols, age does not always correlate to being an optimal candidate for TKA, as it has more to do with a patient’s medical fitness level,” Dr. Ayers said.

“If a patient is in good health, they can undergo the surgery. Based on our findings, orthopaedic surgeons can recommend TKA as an appropriate and life-changing operation for people with advanced arthritis who do not respond to conservative care, even those over 75 years of age.”

The team is currently testing a program that will provide a predictive algorithm based on a patient’s demographics and comorbidities, offering patients an analysis of their expected pain, function, and quality of life scores 1 year after surgery.