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KAT: The Knee Arthroplasty Trial

  • Musculoskeletal disease and trauma

Around 90,000 knee replacements are performed annually in the UK, at an estimated hospital cost of £700 million per year. However, before the KAT trial, remarkably little was known about the actual cost of the procedure, hospital stay or complications in the short, medium or long term, or which type of prosthesis offered the best value for money.

KAT comprises a pragmatic, randomised controlled trial evaluating three knee replacement technologies: metal backing of the tibial component compared with a single high‑density polyethylene component; patellar resurfacing compared with no resurfacing; and polyethylene mobile bearing compared with fixed bearing arthroplasty.

Recruitment was completed in 2003, with more than 2,300 participants randomised across 34 UK centres.

Ten‑year clinical and economic results for the first three comparisons showed that participants had poor functional status and quality of life before surgery, although all study groups demonstrated marked improvement within three months. Around 15% of patients were readmitted to hospital regarding their knee or underwent additional knee surgery within 10 years of their primary operation. There were no statistically significant differences between randomised groups in functional status, quality of life or complications over the first 10 years after total knee replacement.

Patellar resurfacing dominated no resurfacing, non‑significantly improving quality of life and reducing cost. Metal backing improved quality of life at a small cost, at £35 per QALY gained compared with all‑polyethylene. Mobile bearings were associated with increased cost and small improvements in quality of life, costing £1,666 per QALY gained, although there was substantial uncertainty around this conclusion.

KAT papers have been cited in NICE guidelines on patellar resurfacing and osteoarthritis, as well as in reporting guidelines.

Twenty‑year results for the patella comparison have been accepted for publication in The Lancet, and papers on the other comparisons are in preparation.