What does extension lag mean?

What does extension lag mean?

• A. Inability to fully extend the knee
• B. Inability to flex the knee
• C. Pain during extension
• D. Normal passive extension without movement

Answer: (A)

Extension lag means the knee can be moved into full extension passively, but when the person tries to actively straighten the leg, it doesn’t reach full extension. This points to weakness or inhibition of the knee extensor muscles, usually the quadriceps, often after injury or surgery with swelling or nerve/inhibition effects. That’s why the description “inability to fully extend the knee” is the best fit. It’s not about not being able to bend the knee, nor is it necessarily about pain during extension, and it wouldn’t be described as normal passive extension without movement because the key feature is the active failure to reach full extension.

Extension lag means the knee can be moved into full extension passively, but when the person tries to actively straighten the leg, it doesn’t reach full extension. This points to weakness or inhibition of the knee extensor muscles, usually the quadriceps, often after injury or surgery with swelling or nerve/inhibition effects.

That’s why the description “inability to fully extend the knee” is the best fit. It’s not about not being able to bend the knee, nor is it necessarily about pain during extension, and it wouldn’t be described as normal passive extension without movement because the key feature is the active failure to reach full extension.