Effect of adductor canal block on medial compartment knee pain in patients with knee osteoarthritis Retrospective comparative study

Knee osteoarthritis (KOA) is a common disease in middle-aged and elderly people. Pain is the chief complaint of symptomatic KOA and a leading cause of chronic disability, which is most often found in medial knees. The aim of this study is to evaluate the efficacy of pain relief and functional improvement in KOA patients treated with ultrasound-guided adductor canal block (ACB). This is a 3-month retrospective case-controlled comparative study. Two hundred patients with anteromedial knee pain owing to KOA that was unresponsive to 3-month long conservative treatments. Ninety-two patients received ACB with 9mL of 1% of lidocaine and 1mL of 10mg triamcinolone acetonide (ACB group), and 108 continued conservative treatments (control group). The main outcome measure was visual analog scale (VAS) of the average knee pain level for the past one week. Secondary outcomes were the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), the timed up and go test, numbers of analgesic ingestion per day, and opioid consumption per day. During the 3-month follow-up, 86 patients in ACB group and 92 in control group were analyzed. There was no significant difference, with the exception of the duration of symptoms, between the 2 groups in age, sex, body mass index, and Kellgren-Lawrence grade. Repeated-measures analysis of variance and post hoc tests showed improvement of VAS (at month 1), WOMAC(at month 1), and opioid consumption per day (at month 1 and 2) in ACB group. No adverse events were reported. To our knowledge, this is the first study to assess the efficacy of ACB for patients with KOA. ACB is an effective and safe treatment and can be an option for patients who are either unresponsive or unable to take analgesics.