Introduction: Urinary retention is a widely recognised postoperative complication. Although anecdotally lower limb arthroplasty is linked with high rates of urinary retention, there are no current accepted standards for determining which patients are at higher risk and should therefore be offered intra operative catheterisation. Materials and Methods: One hundred patients, 55 females and 45 males, who underwent uncomplicated total hip or total knee replacements at Furness General Hospital were recruited between January and April 2017. Results: Post-operative urinary retention was seen frequently, with 38 patients (38%) requiring post-operative catheterisation. Twenty-one males (46%) developed postoperative retention compared to 17 (30%) of females, representing a statistically significant increase in risk seen in male patients. (p 0.009). Post-operative urinary retention requiring catheterisation was associated with increasing age, with those over 75 years having a significantly higher risk than those less than 75 years irrespective of gender (p 0.04). There was no significant difference in urinary retention rates between patients who had general (n=21) or spinal anaesthetic (n=79) with 33% of GA patients and 39% of spinal anaesthetic patients requiring catheterisation (p 0.17). Conclusion: There are increased rates of urinary retention seen in lower limb arthroplasty patients than those described in the general surgical population, with male patients and all those over 75 years of age having a significantly higher risk. Clinically, it may therefore be sensible to consider offering routine intra operative catheterisation to this cohort of patients.