Relationship between pain and proprioception among individuals with rotator cuff-related shoulder pain

Background

Individuals with rotator cuff-related shoulder pain (RCRSP) have altered proprioception. The relationship between shoulder pain and proprioception is not well understood.

Purpose

This study aimed to investigate the relationship between shoulder pain and proprioception.

Study design

This was a cross-sectional comparative study.

Methods

Twenty-two participants with RCRSP (mean age 27.6 $\pm$ 4.8 years) and 22 matched pain-free participants (23.4 $\pm$ 2.5 years) performed two upper limb active joint position sense tests: (1) the Upper Limb Proprioception Reaching Test (PRO-Reach; reaching toward seven targets) in centimeters and (2) Biodex System at 90% of maximum internal rotation in degrees. Participants performed three memorization and three reproduction trials blindfolded. The proprioception error (PE) is the difference between the memorized and estimation trials. Pain levels were captured pre- and post-evaluation (11-point Likert Numerical Pain Rating Scale). Relationships between PE and pain were investigated using independent t-tests and Spearman rank correlations.

Results

Overall, 22.7% RCRSP participants indicated an increase in pain following the PRO-Reach (X̅ increase of 1.4 ± 1.5 points), while 59% did so with the Biodex (X̅ increase of 2.3 ± 1.8 points), reflecting a clinically important increase in pain. Weak-to-moderate correlations between pain and PEs were found with the Biodex (r = 0.39-0.53) and weak correlations with the PRO-Reach (r = −0.26 to 0.38). Concerning PEs, no significant differences were found between groups with the Biodex (p = 0.32, effect size d = −0.31 [−0.90 to 0.29]). The RCRSP participants demonstrated lower PEs with the PRO-Reach in elevation compared to pain-free participants (global X̅ = 4.6 $\pm$ 1.2 cm vs 5.5 $\pm$ 1.5 cm; superior 3.8 $\pm$ 2.1 cm vs 5.7 $\pm$ 2.9 cm; superior-lateral nondominant targets 4.3 $\pm$ 2.2 cm vs 6.1 $\pm$ 2.8 cm; p = 0.02-0.05, effect size d = 0.72-0.74 [0.12-1.3]).

Conclusions

Individuals with RCRSP demonstrated better upper limb proprioception in elevation, suggesting a change to interoception (sensory reweighting) in the presence of pain.