Shoulder proprioceptive sense of force in chronic anterior instability: performance and clinical associations.

BACKGROUND

Proprioception, our internal awareness of limb position and movement, is essential for shoulder stability through neuromuscular control. Following traumatic anterior instability (TAI), proprioceptive impairments may develop, potentially affecting upper limb function. These deficits vary across individuals. Previous studies have focused primarily on joint position sense and kinesthesia, while sense of force (SoF) deficits in chronic TAI remain largely unexplored. Moreover, clinical assessments are multifactorial and time-limited, and little is known about how SoF relates to common clinical measures. This cross-sectional study aimed to (1) determine whether chronic TAI is associated with shoulder SoF deficits compared with the contralateral side and a control group (CG) and (2) explore potential associations between SoF, maximal voluntary isometric strength (MVIC), and clinical questionnaires used in shoulder instability assessment.

METHODS

Participants aged 18-40 with TAI underwent SoF assessment in both shoulders. A matched CG (n = 37) was tested only on the dominant arm. Proprioceptive accuracy (PA) during SoF testing, MVIC, and shoulder questionnaires (Western Ontario Shoulder Instability Index, Shoulder Instability-Return to Sport after Injury, Disabilities of the Arm, Shoulder and Hand (short version)) were collected for analysis.

RESULTS

The TAI group included 37 participants (27% female, n = 10; 73% male, n = 27), subdivided into non-surgical (TAINS, n = 18) and surgical (TAIS, n = 19) subgroups. Analysis revealed a significant main effect of intensity on PA, F(1,36) = 26.835, P < .001, η2 P = .427, but no significant main effect of group, F(1,36) = 0.545, P > .05, η2 P = .015, nor intensity × group interaction, F(1,36) = 0.131, P > .05, η2 P = .004. A significant main effect of side was observed, F(1,35) = 4.18, P < .05, η2 P = .107, with higher PA score on the affected side (10% ± 7.6) than the unaffected side (8.5% ± 6.8; Cohen's d = 0.196). Only the model for the 20% external rotation condition was statistically significant (adjusted R2 = 0.383; F(2,33) = 11.884,P < .001), with Disabilities of the Arm, Shoulder and Hand (short version) (β = 0.763, P < .001) and Shoulder Instability-Return to Sport after Injury score (β = -0.519, P = .002) emerging as significant predictors.

CONCLUSION

Chronic TAI subjects showed no difference in SoF performance compared with the CG. Associations between SoF, MVIC, and clinical questionnaire outcomes were minimal, emphasizing the importance of interpreting clinical assessments collectively rather than in isolation.