Extension loss after injury or surgery
Failure to regain full extension after injury or surgery may be due to -
- a weakness or inhibition of the extensor muscles (called 'extension lag' or 'quadriceps lag')
- a mechanical cause such as adhesions in the tissues that normally lubricate the joint, or a physical obstruction preventing extension (extension block).
By comparing the extension when seated and actively extending the knee to the situation when prone and passively allowing the knee to extend, one can determine how much of the problem relates to a muscle weakness of inhibition and how much is due to a mechanical problem.
The clinician must determine which of the two possibilities is preventing the patient from fully extending the knee.
