The Knee Society system for evaluating total knee replacements uses separate assessments for knee rating and functional assessment. This eliminates the problem of declining scores due to patient infirmity.
Patient categories:
A: unilateral or bilateral (opposite knee successfully replaced)
B: unilateral, other knee symptomatic
C: multiple arthritis or medical infirmity
Knee Score
|
Parameter |
Finding |
Points |
|
pain |
none |
50 |
|
|
mild or occasional |
45 |
|
|
mild or occasional, stairs only |
40 |
|
|
mild or occasional, walking and stairs |
30 |
|
|
moderate and occasional |
20 |
|
|
moderate and continuous |
10 |
|
|
severe |
0 |
|
range of motion |
|
1 point for each 5°, maximum 25 for 125° |
|
anteroposterior stability (maximum movement in any position) |
< 5 mm |
10 |
|
|
5-9 mm |
5 |
|
|
>= 10 mm |
0 |
|
mediolateral stability (maximum movement in any position) |
< 5° |
15 |
|
|
6 - 9° |
10 |
|
|
10-14° |
5 |
|
|
>=15° |
0 |
|
flexion contracture (deduction) |
5-9° |
-2 |
|
|
10-15° |
-5 |
|
|
16-20° |
-10 |
|
|
> 20° |
-15 |
|
extension lag (deduction) |
< 10° |
-5 |
|
|
10-20° |
-10 |
|
|
> 20° |
-15 |
|
alignment (deduction) |
0-4° |
0 |
|
|
5-10° |
-3 points for each degree |
|
|
11-15° |
-3 points for each degree |
|
|
> 15° |
- 20 |
where:
• deduction for flexion contracture > 20° in AMA Guides is (-20) rather than (-15)
• to get 0 points deduction in flexure contracture, assume < 5° is 0 points
• to get 0 points deduction in extension lag, assume no extension lag is 0 points
• the deduction for alignment can be interpreted in at least 2 ways: (1) 2 separate ranges with points assigned for each degree in that range; (2) the deduction for the second range is added to that for the first range. In the former, an alignment of 9° is assigned a higher deduction than that for 12°. In the latter, an alignment of 14° has a higher deduction than for 16°.
• deduction for alignment of 0-4° and 5-10° are switched in Knee Society guide and the AMA Guide; the AMA Guide pattern was used
total points for knee score =
= (points for pain) + (points for range of motion) + (points for anteroposterior stability) + (points for mediolateral stability) + (minus points for flexion contracture deduction) + (minus points for extension lag deduction) + (minus points for alignment deduction)
knee score =
= MAX (0, total points for knee score)
Interpretation
• maximum score 100 points (well-aligned knee, no pain, 125° of motion, negligible anteroposterior and mediolateral instability)
• minimum score 0
Function Score
|
Parameter |
Finding |
Points |
|
walking |
unlimited |
50 |
|
|
> 10 blocks |
40 |
|
|
5-10 blocks |
30 |
|
|
< 5 blocks |
20 |
|
|
housebound |
10 |
|
|
unable |
0 |
|
stairs |
normal up and down |
50 |
|
|
normal up, down using rail |
40 |
|
|
up and down using rail |
30 |
|
|
up with rail, unable to come down |
15 |
|
|
unable to use stairs |
0 |
|
assistance device (deduction) |
cane |
- 5 |
|
|
2 canes |
- 10 |
|
|
crutches or walker |
- 20 |
where:
• 1 block is approximately 100 meters
total points for function score =
= (points for walking) + (points for stairs) + (minus points for assistance device)
function score =
= MAX(0, total points for function score)
Interpretation:
• maximum score 100 (able to walk an unlimited distance, able to go up and down stairs without use of rail, and without need for an assistance device)
• minimum score 0
Specialty: Surgery, orthopedic
