This is Part 3 of a series of articles on threats to a proper knee surgery recovery. In this installment we discuss achieving full knee extension after knee replacement. I encourage you to explore the other articles in the series which you can find by clicking on the link below.

Physical therapists, surgeons, exercise physiologists, personal trainers all emphasize full terminal knee extension for their knee patients after surgery. Why?

Let’s start with defining our terms. Terminal Knee Extension is achieved when the angle of your leg is 0º when extending it out in front of you. 0º means it is perfectly straight. PTA Yvonne LaCrosse defines extension and flexion in this short video.

Here are five key results of the lack of proper knee straightening. Lack of a straight knee:

We interview Dr. Carl Freeman one of the co-authors of the study who explains the findings of his study as well as explores the value of pre-hab based on a recently published look at pre-habilitation before surgery and how that compares to pre-hab on X10. Dr. Freeman also discusses why the X10 pre-hab program is so much more effective than traditional pre-hab programs.

There is a lot of published research regarding an extension deficit and ACL repair. I thought a few notable facts would be helpful which I share below:

“Knee extension deficit is frequently observed after anterior cruciate ligament reconstruction or rupture and other acute knee injuries. Loss of terminal extension often occurs because of hamstring contracture and quadriceps inactivation rather than mechanical intra-articular pathology. Failure to regain full extension in the first few weeks after anterior cruciate ligament reconstruction is a recognized risk factor for adverse long-term outcomes, and therefore, it is important to try to address it.” (2)

A patient who presents with an extension deficit after an acute knee injury or surgery can be challenging to manage. The medical provider who first evaluates the patient must differentiate between two separate situations: In the “locked knee,” a displaced intra-articular structure mechanically prevents full extension, whereas the “pseudo-locked knee” occurs without the presence of any true mechanical block to motion.(1) Although frequently observed in clinical practice, the pathophysiology of the latter scenario had remained unclear for decades. In 1986 Allum and Jones 1 observed that spasms of the hamstrings were related to an extension deficit after knee injury, but no explanation was given. More recently, there has been increased interest in the subject, and multiple authors have postulated that the extension deficit, also observed after knee surgery, may be due to a process called “arthrogenic muscle inhibition” (AMI). (2, 3) AMI is believed to be responsible for the failure of quadriceps activation that is associated with hamstring contracture. (6)

Extension can be a real issue for both Total Knee Replacement and ACL Repair patients. It can be hard to solve. And there is a condition where fluid (swelling) can play a negative role in recovering extension (called AMI above). This means that we want to eliminate all of the swelling in the joint to achieve full knee function and full extension.

Simply put:

As with infection, deep vein thrombosis, poor flexion, lack of strength, and other health complications, poor knee extension can be managed. This series of articles is all about knowing the facts, the obstacles to a great recovery, so we can avoid them completely. I welcome your thoughts in the comments section below.

We call it a “Meta-Blog.” In these articles we step back and give you a broad perspective on all aspects of knee health. We explore surgery and recovery and such subjects as ‘Lack of Full Knee Extension’.

This is a one-of-a-kind blog. We gather together great thinkers, doers, and writers. And it is all related to Knee Surgery, Recovery, Preparation, Care, Success and Failure. Meet physical therapists, coaches, surgeons, and patients. And as many smart people as we can gather to create useful articles for you. You may have a surgery upcoming. Or in the rear-view mirror. Maybe you just want to take care of your knees to avoid surgery. In all cases you should find some value here. Executive Editor: PJ Ewing ([email protected])