Inclusion Criteria:  Suitable for medial unicompartmental knee arthroplasty Aged between 18 and 75 years inclusive Taller than 1.5m in height (the 10th percentile for the population) Functionally intact anterior cruciate ligament Able to give informed consent Able to return to GJNH for follow-up BMI under 40  Exclusion Criteria:  Inflammatory joint disease e.g. rheumatoid arthritis Previous hip procedure in the previous twelve months Previous knee surgery other than arthroscopy and medial menisectomy Previous ankle surgery Symptomatic foot, hip or spinal pathology Any medical condition limiting normal ambulation e.g. stroke, Charcot-Marie-Tooth disease, severe lymphedema, advanced cardiac disease Unable to read and understand English and follow verbal and visual instructions unless they can bring a relative or friend to all study assessments to act as a translator