Twenty RCTs (n=1,731 patients) were included in the meta analysis. The included trials were generally of good quality, with the mean Jadad score of 3.1 (ranging from 1 to 5 points). Thirteen RCTs performed intention-to-treat analyses.
Short-term follow-up (at week four to eight): Compared with controls, steroid injection was associated with a significant short-term improvement of pain (ES 1.30, 95% CI 0.55 to 2.04; SRM 0.96, 95% CI 0.63 to 1.30) and physical function (ES 0.66, 95% CI 0.03 to 1.30; SRM 1.06, 95% CI 0.45 to 1.66). Based on the evaluation of the effect size, the effect was moderate to large for these outcomes.
Long-term follow-up (at week 48): Compared with controls, steroid injection was associated with a significant long-term increase of pain (SRM -0.28, 95% CI -0.53 to -0.03) and a reduction of physical function (SRM -0.47 (95% CI -0.72 to -0.22). There were no significant differences in the outcomes of pain effect size and physical function effect size between the two groups.
Significant heterogeneity was observed in the four to eight week outcomes of pain effect size (I2 not reported; p<0.001), pain standardised response mean (I2=65.7%; p=0.003) and physical function standardised response mean (I2=87.8%; p<0.001). Results of statistical heterogeneity in the week 48 outcomes were not presented.
Sensitivity/subgroup analyses showed that steroid injections were not significantly better than non-steroidal anti-inflammatory
drugs at short-term follow-up; steroid injections were significantly more effective in acute or sub-acute tendonitis than in chronic tendonitis (p<0.001). Sensitivity analysis did not materially affect the results in terms of location of joint involved and types of steroids.
The main adverse events of steroid injections were transient pain after injection (10.7% of corticosteroid injections) and skin modification (4.0%).
Results evaluating the efficacy of steroid injections at week one to three and 12 to 24 were also reported.