Instability in total knee arthroplasty: loose as a goose

As total knee arthroplasties last longer and are used in younger patients, as well as for a variety of other reasons, greater interest in postoperative tibiofemoral instability has developed. Initial evaluation emphasizing correlation of symptoms and findings together with elucidation of the specifics of the instability are mandatory. Gap inequality, gap asymmetry, and the causes of each are noted. Soft tissue repair or reconstruction alone has not been very successful for such instabilities. Some aspect of revision with component change is generally necessary, and some correction of alignment, gap features, and other issues, with advancement to a higher order of constraint, will generally be necessary.