Abstract Background Although the short-term effects of tumor necrosis factor alpha (TNF-α) and interleukin-17A (IL-17A) inhibition on the structural changes in psoriatic arthritis (PsA) using high-resolution peripheral quantitative computed tomography (HR-pQCT) have been reported, no studies have investigated the long-term structural changes in PsA patients receiving routine care. We reported longitudinal changes of erosions and enthesiophytes using HR-pQCT and their relationship with treatments in PsA patients over a 5-year period. Methods HR-pQCT examination at the second and third metacarpal heads (MCH2 and MCH3) was performed in 60 PsA patients at baseline and after 5 years. The size of each individual lesion was quantified. Erosion and enthesiophyte progression were defined as change exceeding the smallest detectable change (SDC). Results A total of 108 bone erosions and 99 enthesiophytes were detected at baseline. Three new bone erosions but no new enthesiophytes were evident at 5 years. A significant increase in mean (±SD) erosion (0.58 ± 1.50 mm³, P < 0.001) and enthesiophyte (0.47 ± 0.76 mm³, P < 0.001) volume was observed. Erosion and enthesiophyte progression were found in 37/111 (33.3%) and 50/99 (50.5%) lesions, respectively. During this 5-year period, 26 (43%) out of the 60 patients achieved sustained Disease Activity index for PSoriatic Arthritis (DAPSA) low disease activity (LDA) (SDL group, defined as achieving DAPSA-LDA at both baseline and 5 years). Fourteen (23%) out of 60 patients received a TNF inhibitor throughout the 5-year period (TNFi group). Fewer erosions progressed (12/51 [23.5%] vs 25/60 [41.7%], P = 0.047) and the increased in enthesiophyte volume was significantly less (0.28 ± 0.67 vs 0.61 ± 0.80 mm³, P = 0.048) in the SDL group than in the non-SDL group. However, no significant difference between the TNFi and non-TNFi groups was detected in terms of the change in volume or progression of bone erosion and enthesiophyte. Conclusion Damage accrual in terms of bone erosion and enthesiophyte was observed in PsA patients over a period of 5 years despite receiving routine clinical care. Nonetheless, sustained control of disease activity may be able to prevent these bony damages.