Unicompartmental Versus Total Knee Replacement for Medial Compartment Knee Osteoarthritis

For patients with osteoarthritis affecting only the inner part of the knee, surgeons can offer either a partial knee replacement, which resurfaces the worn compartment alone, or a total knee replacement. Both are recommended treatments, but there is no agreement on when to choose one over the other. Partial knee replacement preserves the anterior cruciate ligament and more of the natural knee, and recovery is usually quicker, but it is used in only about one in ten knee replacements in the United Kingdom. Studies comparing the two have mostly relied on patient questionnaires, which may not be sensitive enough to detect differences in how the knee actually functions. Studies that have measured movement directly have concentrated on level walking, which is not demanding enough to separate the two operations. Difficulty with stairs is one of the longest lasting problems patients report after knee replacement. The FLEX-UNI trial will compare the two operations using three-dimensional motion analysis during more demanding everyday activities. Forty patients who are suitable for a partial knee replacement will be randomly allocated to receive either a partial or a total knee replacement. Patients and the researchers measuring their movement will not know which operation was performed. The main measurement is how far the operated knee bends while stepping down from a 20 cm step, measured one year after surgery. Movement during walking, stair climbing, slopes, sitting and standing, and balance will also be measured, along with questionnaires, x-rays, and complications. Results will be compared against measurements from people with healthy knees.

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 the study centre for follow-up * BMI under 40 Exclusion Criteria: * Inflammatory joint disease e.g. rheumatoid arthritis * Previous hip procedure within 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