Knee-lock or Screw-home

Knee-lock or Screw-home

shapeimage_1-29If we are working to maintain full ROM in the joints, then why not lock out the knee?

First it is important to recognize that there are movements that may be contraindicated do to a structural complication but for those with healthy joints avoiding the movement could actually increase the risk of injury.  Two such injuries are Lack of Vastus Medialis Involvement and weakness leading to patella tracking problems, which I was having problems with.  Since I began Locking out my knees in my practice, knee pain and patella tracking problems are resolved which has let me to look deeper into the notion that locking out th e knee is bad especially considering that the normal ROM of a  knee is full flexion to full extension, pain free.


A small loss of flexion of the knee affects gait and puts pressure on the kneecap and possibly cause damage.  While any loss of extension prevents what is referred to as the ‘knee-lock’ or ‘screw-home’ where the leg is able to support the body weight with the quads relaxed. This lock-back or screw-home cannot properly occur if there is any loss of extension and this overloading puts the quads – and the hamstrings under a lot of strain. The body has to rely on muscle and ligament more for support and stability, which can create fatigue, pain and increased risk of injury or re-injury.  Any one who has gone thruPT for 


knee surgery is put thru a series of leg extension exercise in an effort to help regain that full ROM needed to restore and maintain a healthy knee, straight leg is at 0 degrees. A flexed knee is at about 140 degrees. It is a common misconception that 0-140 degrees is a range of motion, but most people have some hyperextension, too, taking their ROM into negative numbers.


•normal ROM is usually minus 5 to 143 degrees in women

•normal ROM is usually minus 6 to 140 degrees in men.

How many times do you hear, don’t hyperextend the knee?  Really?  You think by opening up the knee to its full extension is going to create hyperextension?  I will not go into the anatomy of the knee here, but know that a hyper extended knee is an injury that is the result of a bad fall or impact that pushes the knee beyond extension damaging tendons, and ligaments.

Standing in chronic or constant extension can be harmful but so can keeping the knees soft. If you keep a constant soft knee in your practice you will find excessive tension put on the quads and undo stress to the joint and muscles and ligaments.  BALANCE is what we are looking for.


When you have hyper mobile joints it is very important to learn how to not only control the joint in neutral, but to recover when it does go too far.  But few actually present with this diagnosis and as long as you are moving with in a pain free ROM, who am I or any one to tell you you are hyper extending the knee.  It could be as simple as the shape and curve of the leg bones and have absolutely nothing to do with joint imbalance.


“There is little if any research to indicate that locking out the knee or elbow will cause damage to normal joints with properly performed exercises. In the knee joint, full extension is the position where the least amount of contact occurs between the underside of the patella and the trochlea(3). As the knee goes into flexion the amount of contact increases(1). In the normal, uninjured knee or elbow, full extension is the strongest weight-bearing position during axial loading.”

1. Escamila, R. Knee biomechanics of the dynamic squat exercise. Med. Sci. Sports Exerc. 33(1):127-141. 2001

3. Grelsamer, R.P., and J.R. Klein, The biomechanics of the patellofemoral joint. J. Occup. Sports Ther. 28(5):286-298. 1998



It is important to include the full ROM in your practice, especially the knees ankles and hips.  Ligaments bend, but do not really stretch well and are sensitive to stretching, tearing, pressure, etc.  They really only come into play once the muscle-tendon has been pushed beyond its safe ROM.  According to Vern Gambetta, author of “Athletic Development” and director of Gambetta Sports Training Systems in Sarasota, Fla., move your joints and body in their full range of motion.  Although tendons do not have high ranges of motion, they provide a normal range of motion for all of your joints without compensation of movement


If you go into full extension and if there is not pain, then you are not creating injury.  This flexibility prevents strain and pain and possible injury.  Muscles get stronger faster then tendons and ligaments do, and if we overlook the strengthening aspect of the tendons and ligaments and only focus on the muscles strength we are creating an environment for injury.  .


The only time we are really aware of our tendons and ligaments is when we injure them or over use them and we often neglect the idea of training these tissues to avoid injury.  In order to develop strength and stability in the tendons and ligaments we must do things that stress them.  This creates stronger joints and prepares Today’s Athlete for high intensity workouts and sometimes-just life.  Over strengthening the muscles in relationship to the tendons and ligaments can lead to over stretching and injury.  As we build stronger ligaments, tendons and fascia you help to build a body less susceptible to injury doing sports, whiles stretching or other activities.

The best way to make joint strong is by strengthening the muscles/ligaments around it. By locking, you are giving these muscles a break, Locking out will place stress on your joints, hence making them stronger. If you don’t occasionally lockout, your joints will never be strong and you risk shortening the muscles created a state of chronic flexion.


In our yoga practice we are looking to find a balance between ease and Effort, a balance of strength and flexibility and Mobility.  This will allow your tendons to stay strong, healthy, resilient and better able to withstand the demands put upon it.

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