We investigated the prevalence of psoriatic arthritis and joint complaints in a large population of Italian patients hospitalised for psoriasis. A total of 936 patients were evaluated for psoriatic arthritis according to the European Spondyloarthropathy Study Group (ESSG) criteria. They were visited by a dermatologist who evaluated specific joint signs and symptoms (i.e. arthralgia, stiffness, swelling, ankylosis, paresthesia) and assessed skin disease severity. Information on socio-demographic variables and other factors of clinical interest was also collected. Seventy-one patients (7.7% of the sample) had psoriatic arthritis (PsA). Overall, 90% of patients with PsA referred arthralgia, 70.4% stiffness, 67.7% swelling, 25.4% paresthesia, and 23.9% had ankylosis. However, among patients with plaque psoriasis who did not fulfil the criteria for PsA, 12.3% referred paresthesias, 7% arthralgia, 4.2% stiffness, 3.7% swelling, and 1.2% had ankylosis. Among 114 patients referring arthralgia, 42 (39.6%) did not meet the ESSG criteria for PsA. Therefore, patients with plaque psoriasis refer joint symptoms quite frequently making it difficult to distinguish patients with psoriatic arthritis from patients with joint complaints.