Context and aim: The addition of alpha-2 agonists clonidine and dexmedetomidine to intra-articular (IA) infiltration of local anaesthetics (LA) may prolong the duration of action of analgesia following arthroscopic knee surgery. The objective of this systematic review and meta-analysis was to evaluate the analgesic effect of addition of alpha-2 agonists to LA when used for day case arthroscopic knee surgery. Methods: PubMed, EMBASE, Cochrane Library, Google Scholar, conference abstracts and bibliographic references were searched for RCTs comparing IA LA to IA LA+ adjuvant. The primary outcome was the duration of analgesia (determined by the time to first request for additional analgesia post-operatively). Secondary outcomes were Visual Analogue Scale (VAS) scores at various time intervals, opiate consumption over 24 h and incidence of hypotension and bradycardia. The data were analysed using RevMan software. Results: Eight trials (390 patients) were included with patients receiving dexmedetomidine and clonidine in addition to LA. Alpha-2 agonists significantly prolonged the duration of action of LA [SMD 3.00 [95% CI2.39, 3.62] (p < 0.00001)] (Mean Difference 282 min). VAS scores were statistically significantly lower at one [SMD À1.06 [95% CI À1.98, À0.13] (p = 0.02)], two [SMD À1.29 [95% CI À2.11, À0.47] (p < 0.002)] and eight hours [SMD À0.86 [95% CI À1.25, À0.47] (p < 0.0001)], when alpha-2 agonists were used. Total opiate consumption was reduced in the experimental group (SMD À3.19 [95% CI, À4.74, À1.64] (p < 0.0001)] (Mean Difference 15.45 mg). There were no significant differences in adverse effects. Conclusions: Addition of alpha-2 agonists to IALA significantly prolongs duration of analgesia and reduces VAS scores in the immediate postoperative period following day case arthroscopic knee surgery.