Total hip replacement surgery is a very successful operation with good long-term results. Hip resurfacing arthroplasty is offered as a treatment option for young and active patients with osteoarthritis of the hip. It has been proposed as a treatment option for younger patients because of claims that it preserves femoral bone stock and has better functional outcomes. The assessment of gait after hip replacement surgery may be able to determine functional differences between patients who have undergone total hip replacement / arthroplasty (THA) versus hip resurfacing.

A group of 58 patients, part of a ungoing randomized trial comparing resurfacing hip arthroplasty to metal-on-metal total hip arthroplasty, will be invited to a single gait analysis on a trendmill. All patients have reached a follow up of five years. Patient 's gait will be assessed during two walking sessions, in both sessions spatio-temporal, kinetic and kinematic parameters will be recorded.

• At first when flat walking with increasing speeds to their top walking speed.
• Secondly: when walking at a fixed speed with an increasing incline to their top walking incline.

Inclusion Criteria:

• Patient part of randomised controlled trial (RCT) of hip resurfacing versus MoM total hip arthroplasty for symptomatic osteoarthritis of the hip
• Patient must be able to consent to the study (written informed consent)
• Patients who are functioning well post-operatively and not under routine follow up
• Patients who are able to walk without any safety rail assistance on the treadmill

Exclusion Criteria:

• Patient not originally randomised during an RCT of hip resurfacing versus MoM total hip arthroplasty
• Patients who suffer from any neurological or musculoskeletal conditions that might make a gait test dangerous.
• Patients whose cognitive function prevents them from understanding the study
• Patients who have had or are awaiting revision surgery for their hip