Assessment of the structural validity of three foot and ankle specific patient-reported outcome measures.

Background: The structural validity of the Lower extremity functional scale (LEFS), the Visual analogue scale foot and ankle (VAS-FA), and the Western Ontario and McMaster Universities osteoarthritis index (WOMAC) has not been compared earlier in patients after foot and ankle surgery.

Methods: Altogether 165 previously operated patients completed the foot and ankle specific instruments, the 15D health-related quality of life (HRQoL) instrument, and general health (VAS).

Results: The LEFS, the VAS-FA and the WOMAC had slight differences in their measurement properties. The VAS-FA had the best targeting and coverage. All three foot and ankle measures accounted for mobility and usual activities when compared to the different aspects of generic HRQoL.

Conclusions: The LEFS, the VAS-FA and the WOMAC have relatively similar psychometric properties among foot and ankle patients, yet the VAS-FA provides the best targeting and coverage.