Twenty RCTs were included in the review with 895 participants of which 458 received local anesthetic.
The median score for quality was 3 (range 2-5). Twelve of twenty studies showed improved pain relief after treatment.
In ten of the 12 positive studies, pain scores were significantly lower in the treatment groups compared with the control groups with visual analog scale (VAS) score reductions of between 10 and 35 mm early (1-4 hours) postoperatively.
WMD for 12 trials confirmed a statistically significant but less clinically important effect on postoperative pain scores, WMD 11 mm (95% CI: 14, 7 mm) in favour of the treatment groups compared with the control groups. Heterogeneity was not significant (p = 0.80).
In nine studies, the consumption of supplementary analgesics was reduced by 10-50% during observation periods of up to 4 hours. However, in most cases, the analgesic requirements were small to moderate.
Only in two of six studies, where time to first analgesic request was evaluated, a significant prolongation of pain relief was observed as lasting between 30 and 50 minutes.
The difference in mean dose between positive and negative studies, was not statistically significant, (P = 0.196, Mann-Whitney U test). In the study where 200 mg of prilocaine was instillated intra- articularly, no effect on postoperative pain was observed.
The influence on immediate recovery and ambulation of intra-articular local anesthesia was examined in 8 studies. One study found a statistically significant improvement where patients in the treatment group regained their ability to walk 30 minutes before patients in the control group. However, in the other 7 studies no effect of intra-articular local anesthesia on the ability to walk, normal activities, home readiness, or duration of ambulatory hospital stay was observed.
No side effects or signs of toxicity attributable to the intra- articular local anesthesia were reported (9 studies). No pattern of a possible influence of the type of surgical procedure on the effect of intra-articular local anesthesia on post-operative pain was observed.