Continuous peripheral nerve blockade is a common technique in the analgesic management for many procedures. Leakage of local anaesthetic from around the nerve catheter insertion site can increase the chance of catheter dislodgement, risks infective complications, and could divert anaesthetic away from the nerve causing the block to fail. We conducted a randomised controlled trial to assess whether the type of nerve catheter influenced local anaesthetic leak rate. One hundred and ten patients scheduled for elective unilateral total knee arthroplasty were randomised to receive a perineural catheter with either a catheter over needle (CON) system (Pajunk (R) E-Cath) (Pajunk (R) GmbH, Medizintechnologie, Geisingen, Germany), or catheter through needle (CTN) system (Pajunk (R) SonoLong) (Pajunk (R) GmbH, Medizintechnologie, Geisingen, Germany). There was no statistically significant difference in the rate of leaking catheters between groups (CON 1.8% versus CTN 3.7%; P=0.618), however, the overall leak rate was much lower than anticipated from pilot data. The CON system was on average faster to insert (CON 357 seconds versus CTN 482 seconds; P=0.004), but associated with poorer needle visibility under ultrasound (Likert scale 1-5, mean [SD], CON 3.31 [0.96] versus CTN 3.89 [0.84]; P=0.001). All seven instances of inadvertent catheter dislodgement occurred in the CTN group (P=0.006). There was no statistically significant difference between groups in the proportion of patients who had adequate analgesia on day one (CON 80% versus CTN 86.5%; P=0.294) and day two postoperatively (CON 85.5% versus CTN 91.8%; P=0.369). Our findings show the overall leak rate to be very low with both catheter systems; however, the CON system may have advantages in terms of speed of use and rate of inadvertent catheter dislodgement.