Table 1.

Knee function assessment scale.

Normal Knee Function (All of the following must be met)	Mildly Limited Knee Function (Meet all* of the following and 1 or more of the others)	Severely Limited Knee Function (Meet any 1 of the following)
No conscious pain, stiffness, or instability in the knee when resting, exercising, or exercising	Mild knee pain (VAS < 4) and/or mild swelling during or after exercise, without signs of locking or instability, and the pain or swelling is relieved by rest	More than moderate knee pain (VAS ≥ 4) and/or significant swelling during or after exercise, accompanied by stiffness and instability, and the pain or swelling does not resolve after 2 weeks of rest and symptomatic treatment.
Normal gait	Normal gait*	Abnormal gait
Bilateral thigh circumference difference <5%	Bilateral thigh circumference difference ≥5% but <10%	Bilateral thigh circumference difference ≥10%
Floating patella test (−)	Floating patella test (−)*	Floating patella test (+)
Patellar compression test (−) and patellar grinding test (−)	Patellar compression test (+) or patellar grinding test (+)	–
Knee joint stabilization	Knee joint stabilization*	Knee joint instability
The injured knee joint has no limitation to flexion and extension, and its active and passive flexion and extension activities are the same as the uninjured side	The injured knee joint is not restricted in extension, and the bilateral difference between active and passive knee flexion is <10˚	The injured knee joint is restricted in extension, or the bilateral difference between active and passive knee flexion is ≥10˚
Knee flexor and extensor strength (Grade Ⅴ)	Knee flexor and extensor strength (Grade Ⅴ)*	Knee flexor or extensor strength (less than Grade Ⅴ)
LSI ≥ 85% in any of the following: one-legged single jump, one-legged triple jump, one-legged cross jump, 6-meter timed one-legged jump	LSI < 85% in all of the following: one-legged single jump, one-legged triple jump, one-legged cross jump, 6-meter timed one-legged jump	–
Knee imaging is normal or shows no evidence of clinically significant changes	Knee imaging is normal or shows no evidence of clinically significant changes*	Knee imaging shows clinically significant changes

VAS, visual analogue scale; LSI, limb symmetry index.

^*Key test items in knee function assessment.