BACKGROUND: The analgesic effect of the adductor canal block (ACB) after knee surgery has been evaluated in a number of trials. We hypothesized that the ACB would provide substantial pain relief to patients responding with moderate to severe pain after arthroscopic knee surgery.

METHODS: Fifty subjects with moderate to severe pain after arthroscopic knee surgery were enrolled in this placebo-controlled, blinded trial. All subjects received two ACBs; an initial ACB with either 30 ml ropivacaine 7.5 mg/ml (n = 25) (R group) or saline (n = 25) (C group) and after 45 min a second ACB with the opposite study medication, according to randomization. Primary outcome was pain during 45 degrees active flexion of the knee at 45 min after the first block, assessed on a 0-100 mm visual analogue scale. Secondary outcome measures were: pain at rest and during flexion of the knee, worst pain experienced during a 5-m walk, patient's evaluation of muscle strength during walk, and amount of sufentanil administered during the 90-min study period.

RESULTS: Regarding primary outcome, mean pain score difference between groups was 34 (95% CI: 25 to 44) mm, P < 0.001, in favour of the R group. At rest, mean pain score difference was 32 (23 to 41) mm, P < 0.001, and during walk: 21 (6 to 36) mm, P = 0.01 in favour of the R group. There were no differences between groups regarding other secondary outcome measures.

CONCLUSION: The ACB is a relevant option for patients with moderate to severe pain after arthroscopic knee surgery.