BACKGROUND:
Stiffness is an uncommon but disabling problem after total knee
arthroplasty. The prevalence of stiffness after knee replacement has not been
well defined in the literature. In addition, the outcomes of revision surgery
for a stiff knee following arthroplasty have not been evaluated in a large
series of patients, to our knowledge. The purposes of this study were to
define the prevalence of stiffness after primary total knee arthroplasty and
to evaluate the efficacy of revision surgery for treatment of the
stiffness.
METHODS:
We defined a stiff knee as one having a flexion contracture of 15°
and/or <75° of flexion. Two separate groups were evaluated. First, the
results of 1000 consecutive primary total knee replacements were reviewed to
determine the prevalence of stiffness. Second, the results of fifty-six
revisions performed because of stiffness, sometimes associated with pain or
component loosening, after primary total knee arthroplasty were evaluated.
RESULTS:
The prevalence of stiffness was 1.3%, at an average of thirty-two months
postoperatively. The patients with a stiff knee had had significantly less
preoperative extension and flexion than did those without a stiff knee (p <
0.0001). There were no significant differences in age, gender, implant design,
diagnosis, or the need for lateral release between the patients with and
without stiffness. The second cohort, of knees revised because of stiffness,
were followed for an average of forty-three months. The mean Knee Society
score improved from 38.5 points preoperatively to 86.7 points at the time of
follow-up; the mean Knee Society function score, from 40.0 to 58.4 points; and
the mean Knee Society pain score, from 15.0 to 46.9 points. The mean flexion
contracture decreased from 11.3° to 3.2°, the mean flexion improved
from 65.8° to 85.4°, and the mean arc of motion improved from
54.6° to 82.2°. The arc of motion improved in 93% of the knees, and
flexion increased in 80%. Extension improved in 63%, and it remained unchanged
in 30%.
CONCLUSIONS:
The prevalence of stiffness in our series of 1000 primary knee
arthroplasties was 1.3%. Revision surgery was a satisfactory treatment option
for stiffness, as the Knee Society scores improved, the flexion contractures
diminished, and 93% of the knees had an increased arc of motion. However, the
results suggest that the benefits are modest.