Patients with knee osteoarthritis who later underwent total knee replacement did not report worse spine-related outcomes one year after lumbar fusion than patients who did not have a subsequent knee replacement, a retrospective study found. The researchers had expected the later-replacement group to report worse disability and function, but the main comparison did not show that pattern.
What the researchers compared
Investigators reviewed records from one tertiary center between 2016 and 2025. They included patients with knee osteoarthritis who underwent lumbar fusion and had completed a one-year ODI score. Patients with hip osteoarthritis at the time of surgery or a previous total knee or hip replacement were excluded.
The final cohort contained 148 patients: 104 in the no-subsequent-TKA group and 44 in the group that later underwent TKA. Researchers divided the patients according to future arthroplasty status, then compared demographics, clinical variables and outcomes using descriptive statistics, chi-squared tests and t-tests. A P value below 0.05 was the reported threshold for statistical significance.
ODI was the study's main patient-reported disability measure. It was recorded before surgery and at 3, 6 and 12 months. The main endpoint was the difference in 12-month ODI. Back and leg VAS scores, along with the number of revisions and time to revision, were secondary outcomes.
The main result
Before surgery, ODI scores were similar: 42.9 in the no-subsequent-TKA group and 46.8 in the later-TKA group. At 12 months, the scores were 21.9 and 27.2, respectively, a difference that was not statistically significant, with P = 0.137.
The reported changes from baseline were also similar, at -20.96 and -19.61 points in the two groups, with P = 0.730. In practical terms, patients who later had knee replacement did not show a clearly different one-year change in the spine disability score.
Pain scores told a similar story. Before surgery, VAS Back scores were 6.22 and 6.84, while VAS Leg scores were 6.83 and 6.53. Neither comparison was statistically significant, and postoperative back and leg scores followed similar trends, with all reported P values above 0.05.
A difference in knee severity
The groups did differ in the severity of knee osteoarthritis at the time of spine surgery. Grade 4 knee osteoarthritis on the Kellgren-Lawrence scale was recorded in 56.8% of later-TKA patients, compared with 20.2% of patients who did not later undergo TKA. The difference had P < 0.001. The average interval between lumbar fusion and knee replacement in the later-TKA group was 679 days.
The measured demographic and comorbidity variables did not show a significant difference. Average age was 64.6 years in the no-subsequent-TKA group and 65.5 years in the later-TKA group; women made up 55.8% and 50.0%, respectively. The analysis reported no significant differences by age, race or sex, and found no significant differences in diabetes, smoking, osteoporosis or overall comorbidity score.
No clear difference in surgical follow-up
Perioperative and revision measures also did not differ significantly. The groups were similar in surgical approach, preoperative diagnosis, number of levels fused and revision count. The reported time to revision was 897 days versus 1,736 days, but that comparison did not reach statistical significance, with P = 0.088. Intraoperative complications and readmissions within 90 days also showed no significant between-group difference.
What the findings can and cannot say
The authors interpret the findings as showing that knee osteoarthritis, or the possibility of a later knee replacement, should not be considered a contraindication to lumbar fusion. Their conclusion rests on comparable 12-month spine-specific patient-reported outcomes and similar revision findings.
The study cannot determine whether one operation should come before the other or whether the timing of knee replacement affects recovery. It was a retrospective review from a single center, so selection bias and limited generalizability are possible. The later-TKA group had only 44 patients, which may have made modest differences harder to detect, and patient-reported follow-up stopped at 12 months. The no-subsequent-TKA group may have included people with milder knee disease or barriers to surgery, while manual grading of some knee images may have introduced variability.
Paper data and sources
Original title: Subsequent Knee Arthroplasty Does Not Influence Patient-Reported Outcomes Following Lumbar Fusion
Authors: Mathew J, Miloh R, Ng M et al.
Journal/Repository: Global Spine Journal
Status: Peer-reviewed
First online: 2026-10-11
DOI: Not available
Original paper · Full text