Effectiveness of eccentric strengthening in the treatment of lateral elbow tendinopathy: a systematic review with meta-analysis

Key points

1. 01Short-term pain reduction favored eccentric strengthening with a large pooled effect size (SMD 1.12, CI: 0.31-1.93)
2. 02Short-term function improvement also favored eccentric strengthening with a large effect size (SMD 1.22, CI: 0.25-2.18)
3. 03Strength outcomes were not significantly improved by eccentric strengthening at any time point
4. 04All long-term (intermediate) outcomes for pain, strength, and function were non-significant
5. 05Results had very high heterogeneity (I2 up to 98%) and sensitivity analyses reduced effect sizes substantially

How it was conducted

Design

Systematic review with meta-analysis (random effects model)

Databases searched

Embase, PubMed, Google Scholar, CINAHL, Cochrane Central Register of Controlled Trials (searched December 2018)

Included studies

8 articles (5 RCTs, 3 quasi-experimental trials)

Participants

504 patients total (218 experimental, 286 control); mean ages 35-50 years; all with symptoms lasting more than 3 weeks

Comparisons

Eccentric strengthening (alone or as adjunct) vs. other strengthening forms or pain-relieving modalities

Primary outcomes

Pain (VAS), grip and wrist extension strength, and upper extremity function (DASH, TEFS, PRTEE, PRFEQ)

What they found

• Immediate pain: pooled SMD 1.12 (CI: 0.31-1.93, P < .01), I2 = 93%
• Immediate function: pooled SMD 1.22 (CI: 0.25-2.18, P = .01), I2 = 95%
• Immediate strength: pooled SMD 1.14 (CI: -0.23 to 2.52, P = .10), I2 = 97% - non-significant
• Strengthening subgroup immediate pain (all 6 studies): pooled SMD 1.00 (CI: -0.01 to 2.01, P = .05), I2 = 93%
• Sensitivity analysis of strengthening subgroup for pain (outlier removed): pooled SMD 0.51 (CI: -0.18 to 1.19, P = .15) - non-significant
• Sensitivity analysis of strengthening subgroup for function (two outlier studies removed): pooled SMD -0.07 (CI: -0.63 to 0.49, P = .81) - non-significant
• Intermediate pain: pooled SMD 1.27 (CI: -0.05 to 2.60, P = .06) - non-significant, I2 = 96%
• Intermediate strength: pooled SMD 1.31 (CI: -0.82 to 3.45, P = .23) - non-significant, I2 = 98%
• Intermediate function: pooled SMD 1.01 (CI: -0.25 to 2.28, P = .12) - non-significant, I2 = 96%
• Mean PEDro score of included studies was 6 out of 10 (range 4-7)

Limitations

• Only 8 studies included, with very high heterogeneity (I2 up to 98%) making pooled results unreliable
• Most studies used eccentric strengthening as an adjunct to other treatments, so its isolated effect cannot be determined
• Strengthening regimes varied widely in duration (3-12 weeks), supervision, and load progression, and none followed Consensus on Exercise Reporting Template guidelines
• Small sample size of studies limits detection of publication bias via funnel plots; 3 of 8 studies were quasi-experimental without randomization

Why it matters

For patients

Eccentric wrist strengthening exercises may reduce pain and improve hand function in the short term, but evidence is too inconsistent to guarantee long-term benefit and the best exercise dose is still unknown.

For clinicians

Eccentric strengthening programs of at least 6 weeks duration with 3 sets of 10-15 repetitions and pain no greater than 5/10 VAS appear to offer the most benefit, but clinicians should interpret pooled results cautiously given very high heterogeneity and reliance on adjunct therapy designs.

For readers

This meta-analysis provides preliminary support for eccentric exercise in tennis elbow, but the small number of heterogeneous studies and inconclusive long-term results mean stronger high-quality RCTs are still needed before firm treatment recommendations can be made.