Global functional and disability are equivalent for psoriatic arthritis (PsA) and rheumatoid arthritis (RA) despite lower levels of peripheral joint damage in PsA for equivalent disease duration.1 Turner et al2 have recently shown that RA is associated with moderate to high levels of foot and ankle-related impairment and disability. We have extended this observation to patients with PsA and included provision of foot care.

A total of 104 consecutive patients with PsA (60 women, 44 men) of mean (SD) age 51 (12) years and a mean disease duration of 10 (9) years were assessed by a single clinician (DET). Foot and ankle-related impairment and disability were measured using the Foot Impact Scale for Rheumatoid Arthritis (FIS-RA).3 Standard clinical indices, visual analogue scales and clinical examination were used to measure or diagnose: self-reported foot pain, global pain and health status; the number of tender and swollen foot joints; forefoot and rearfoot deformity; enthesitis involving the Achilles tendon, plantar fascia and tibialis posterior tendon; dactylitis; and skin psoriasis and nail dystrophy. Current foot care, disease-modifying antirheumatic drug (DMARD) and biological therapy were recorded.

The main clinical findings are shown in table 1. The results show that nearly two-thirds of patients with PsA report foot pain and that a moderate to high level of related impairment and disability are present. Deformity in the forefoot such as hallux valgus, claw and hammer toe occurred more frequently (involving 95% of patients) and with greater severity than in the rearfoot (predominantly pes planovalgus in 65% of cases). Foot joints were mildly tender but swelling was uncommon. In contrast, enthesitis was frequently present with tibialis posterior involved in over one-third of cases. Dactylitis was observed in nearly one-quarter of patients. Skin psoriasis and nail dystrophy were found in 8% and 13% of cases, respectively. Mild to moderate levels of patient self-rated global pain and health status was observed. DMARD use was high and 12 patients received biological therapy.

The novel finding in this study is that PsA is associated with moderate to high levels of foot-related impairment and disability; despite this, about one in five patients receive foot care. In addition, the observed frequency of specific clinical features support those described in other observational studies.4 This result further extends the observation that inflammatory joint conditions lead to significant impairment and functional loss at important peripheral joint sites such as the foot. Indeed, the FIS-RA scores reported for this PsA cohort are similar to those reported in RA patients with established disease of ≤10 years.2 While deformity, joint swelling and tenderness may be milder in PsA than in RA, for example, the contribution of other factors such as enthesitis and skin and nail psoriasis, as recognised by Sokoll et al1 in a global model of disability, may also be important to foot-related disability.

In conclusion, PsA is associated with clinically important levels of foot and ankle-related impairment and disability. We therefore recommend that greater attention is paid to the feet of these patients and that appropriate treatment is provided for inflammatory joint and skin lesions as well as associated mechanical problems.