Minimal Clinically Important Difference After Triamcinolone Acetonide Injection for Knee Osteoarthritis

Objective: – This study aimed to define the minimal clinically important difference (MCID) after triamcinolone acetonide (TA) injections for knee osteoarthritis, see if the value changes over time, and report the proportion of patients achieving MCID monthly for 6 months.Study Design: – Retrospective case series; level of evidence, 4.Setting: – One large university-affiliated practice (13 providers).Patients (or Participants) – Two hundred seventy-seven patients receiving TA (40 mg) with 4cc 1% lidocaine for knee osteoarthritis (OA) were retrospectively reviewed.Intervention: – Patients receiving TA (40 mg) with 4cc 1% lidocaine for knee OA.Main Outcome Measure: – Knee Injury and Osteoarthritis Outcome Score (KOOS) preinjection and monthly for 6 months. MCID values, representing moderate clinical improvement, were calculated as 0.5 standard deviations from preinjection scores.Results: – Of 277 injections (116 men, 161 women; mean age 61.3 years), MCID values varied across KOOS subscales (7.98-12.35). At the 1-month through 6-month follow-ups, the proportion of patients reaching the MCID on the KOOS pain scale was 50.5%, 47.7%, 36.2%, 37.1%, 44.8%, and 39.4%, respectively. Twenty-three percent of patients received a repeat injection within 6 months. Patients who did not meet the calculated MCID for pain by 1 month had a 2.19 times higher odds ratio of receiving a repeat injection within 6 months.Conclusions: – This study establishes MCID values for KOOS subscales in patients with knee OA receiving TA injections using a distribution-based method, which are similar regardless of duration of follow-up within 6 months. Patients can expect significant pain improvement within the first month, with declining effects thereafter. Lack of early pain improvement correlates with a higher likelihood of repeat injection, supporting the need for follow-up assessments to guide ongoing treatment.