Risk classification for primary knee arthroplasty.

We devised a 4-group classification for primary TKA patients: C0, fit patient, simple arthritis; CI, fit patient, complex arthritis; CII, medically unfit patient with simple pattern; and CIII, unfit patient with complex arthritis. Patient fitness and arthritis complexity were based on the literature. One hundred twenty-two patients, operated on by the senior author, were retrospectively placed into one of these 4 groups.