Introduction. New methods to reduce inpatient stay, post-operative complications and recovery time are continually being sought in surgery. Many factors affect length of hospital stay, such as, analgesia, patient and surgeon expectations, as well as provision of nursing care and physiotherapy. Development of the use of postoperative local anaesthetic infiltration delivered intra-articularly by a catheter appears to be an effective analgesic method which reduces patient's opioid requirements and allows early physiotherapy without motor blockade of muscles. Our study aimed to explore if the use of local anaesthetic infiltration intra-articularly following joint athroplasty affected the patient's duration of hospitalisation. Methods. Looking retrospectively at arthroplasty audit data, we compared two groups of age and sex-matched patients who underwent primary hip arthroplasty (replacement and resurfacing) and knee arthroplasty performed by a single surgeon using the same surgical techniques. The surgeon began to utilize local anesthetic infiltration intra-articularly in 2009. The first group included patients operated on the year prior to the change and the second group were those operated on within a year of the change of practice. There were 103 patients (27 resurfacings, 28 knees, 48 hips) in the local anaesthetic group and 141 patients (48 resurfacings, 36 knees, 64 hips) in the non-local anaesthetic group. The length of stay was investigated for plausible Normality using the Shapiro Wilks statistic. Between-treatment group differences were examined using one-way analysis of variance (ANOVA). Factors observed were, use of local anaesthetic (yes/no), joint (hip/knee) and day of surgery (weekend/not weekend). Between treatment group differences in gender and complications were investigated using Chi-squared methods. Results. Patients who received local anaesthetic had shorter stays, irrespective of the joint or day of operation. Patients undergoing hip arthroplasty discharged sooner when local anaesthetic was used compared with those without (mean 4.0 days and 4.4 days respectively P=0.04). Patients undergoing knee replacement also discharged sooner when local anaesthetic was used compared with those without (mean 4.9 days and 6.1 days respectively P=0.09). When knee and hip figures were combined and analysed to measure the significance of effects of treatment on the length of stay, local anaesthetic use was found to be statistically significant in reducing length of stay (P=0.01). There were no between-treatment group differences in proportions of complications, gender or day of surgery. Conclusion. The findings of this study highlight that local anaesthetic infiltration reduces duration of in-patient stay following knee and hip joint athroplasty and there is no associated significant increase in immediate post-operative complications