Validity and reliability of the Turkish version of the 20-item jaw functional limitation scale

Purpose: This study aimed to translate the 20-item Jaw Functional Limitation Scale (JFLS-20) into Turkish (JFLS-20-TR) and investigate the psychometric properties of the JFLS-20-TR.

Methods: This study included 232 patients with temporomandibular disorder (TMD) and 130 individuals without TMD. Structural (with confirmatory factor analysis [CFA]), convergent (with pain intensity, Fonseca Anamnestic Index [FAI], and Oral Health Impact Profile [OHIP-14]), discriminant (with maximum mouth opening [MMO]) and known-group validity were investigated to assess the construct validity. Cronbach's alpha for internal consistency and the intraclass correlation coefficient (ICC_2,1) for test-retest reliability were calculated. Additionally, content and face validity, smallest detectable change (SDC₉₅), and floor/ceiling effects were evaluated.

Results: According to CFA, the model fit indices were acceptable for JFLS-20-TR, confirming structural validity. Strong correlations were found between the global and subdomain scores of the JFLS-20-TR and pain intensity (r ≥ 0.80), FAI (r ≥ 0.83), OHIP-14 (r ≥ 0.76), and MMO (r ≥ -0.79) scores, confirmed the convergent and discriminant validity of the JFLS-20-TR. In addition, JFLS-20-TR differentiated between patients with TMD and individuals without TMD (p < .05). Internal consistency (Cronbach's alpha values: 0.91-0.93) was excellent, and test-retest reliability (ICC_2,1 values: 0.91-0.95) was high. Content and face validity were satisfactory. The SDC₉₅ values ranged from 0.79 to 1.43. No floor or ceiling effects were observed.

Conclusion: The JFLS-20-TR is a valid, reliable, and useful tool for assessing jaw functional limitations in Turkish-speaking patients with TMD.