Knee extensor functional demand in individuals with knee osteoarthritis.

Area of Science:

• Biomechanics
• Kinesiology
• Orthopedics

Background:

• Knee extensor (KE) weakness is common in knee osteoarthritis (KOA), potentially causing disability.
• Increased muscle functional demand and compensatory gait strategies are linked to KOA disability.
• Muscle functional demand is the percentage of maximal strength utilized during a task.

Purpose of the Study:

• Quantify KE functional demand in individuals with KOA.
• Assess the impact of walking speed on KE functional demand.
• Examine relationships between KE functional demand and relative joint work.

Main Methods:

• Gait analysis was performed on 14 individuals with symptomatic KOA at preferred and faster walking speeds.
• Isokinetic dynamometry measured KE maximum voluntary isometric torque.
• KE functional demand, relative joint work, and powers were calculated; statistical analyses included paired t-tests and Pearson's correlation.

Main Results:

• KE functional demand increased significantly from 36.0% at preferred speed to 49.8% at faster speed (p < 0.05).
• Knee flexion moment also increased significantly with faster walking speed (p < 0.001).
• Significant correlations were found between faster speed KE functional demand and relative ankle negative power (r = -0.57) and positive work (r = 0.66) (p < 0.05).

Conclusions:

• As KE functional demand approaches 50% of capacity, individuals with KOA may reduce knee effort.
• Ankle-based compensation strategies are employed to meet increased walking demands in KOA.
• Altered joint work and power distribution suggest adaptive mechanisms in KOA gait.