Quadriceps activation failure.

Not being able to properly tighten your upper leg (quadriceps) presents difficulties during rehabilitation after knee surgery, especially during a anterior cruciate ligament rehabilitation. This results in your inability (or inability) to actively extend your knee. There are several factors that contribute to quadriceps activation failure. Fortunately, we also have good techniques for reteaching the conscious control of the quadriceps. This recurs in every knee rehabilitation. Especially in the first phase after surgery. In this blog, we'd like to tell you more about the background of quadriceps activation failure and the options we have for treating it properly.

The quadriceps femoris is a four-headed muscle at the front of the thigh. These muscles mainly provide knee extension. The rectus femoris is the only one that also has a function over the hip because it has its attachment above the hip joint. This helps with hip flexion. The quadriceps are important in our movement pattern because proper knee extension and sufficient control and strength are needed for various daily activities. Think of activities such as walking, running, getting up from a chair but also climbing stairs. We also see that proper stretching and control of the quadriceps are important for getting a quiet knee (no swelling, pain, heat) after knee injury or knee surgery.

Trochantor major syndrome

Causes for quadriceps activation failure

In many knee injuries but certainly after virtually every knee surgery, quadriceps activation failure is seen at the onset. In the first phase of knee rehabilitation, much attention is paid to regaining this activation. This is because it is known that being able to stretch properly is very important to also be able to walk properly. In addition, we see that people with good knee extension are more satisfied with their rehabilitation than those who do not get good extension. A number of factors are known to have a relationship with quadriceps activation failure. For example, we see that after knee surgery, people move and load much less than normal. This causes a rapid decrease in muscle strength and muscle mass, making it more difficult to control the muscles. Something that is also seen as a common cause for quadriceps activation failure is AMI (arthogenic muscular inhibition) .AMI is a reflex response after surgery or knee injury. The term represents the inability to tighten the muscle for no apparent anatomical reason. In fact, there is no damage to the muscle or to the nerves that control the quadriceps. In practice, we see quadriceps activation failure persisting long after the onset of these symptoms. AMI is likely the result of a protective mechanism after severe knee injury. However, quadriceps activation failure can significantly interfere with the rehabilitation process. A natural phenomenon but not always useful.

Motor control

Motor control is a fancy word for control over the direction and movement of our body. Among other things, our central nervous system plays an important role in this along with the various sensors in muscles and tendons. In quadriceps activation failure, we see that the nerve stimulus that provides control of the muscle cannot be processed as well or at all. By training, we can increase this stimulus frequency, resulting in a stronger tightening of the muscle.


Physical therapy for quadriceps activation failure


At Fysio Fitaal in Tilburg we use NMES (neuromuscular electrostimulation). By means of electrodes we give an extra impulse from the outside which causes a better tightening of the muscle. It is as the name says a neuromuscular tool, we mainly try to influence the stimulation which causes the muscle to tighten. In this way we stimulate the conscious tightening and relaxing of the upper leg muscles. This is basically always done actively, so while you are exercising yourself. We can also use exentric exercise therapy during rehabilitation. Muscle tightening can be concentric, eccentric and isometric. Concentric means the muscle shortens. Eccentric means the muscle delivers force while the muscle fibers lengthen, and isometric is when you deliver force in the same position, so the muscle does not shorten or lengthen. A muscle can deliver more force eccentrically than concentrically alone. So you can brake more pounds than lift them up. Eccentric training is an effective method to improve quadriceps activation and strength.

Advice from us. What can you do yourself?

So regaining good control of the quadriceps control is important for your movement pattern, but also the for the progress of your rehabilitation. Do you have good control of the leg? Then you can work on a good gait pattern and the next steps in your rehabilitation. We have listed some exercises that can be helpful in learning quadriceps control.

Exercises you can do at home! 

Exercise 1: learning to tighten quadriceps while seated.

You sit on a mat (the floor) and bring the toes toward yourself. This brings the knee into full extension and you tighten the thigh muscles. You lift the leg and slightly and hold this for a few seconds. Then you lower the leg again, bringing the leg back to a relaxed position. The toes move away from the body. And the upper leg relaxes again. You do this several times in total succession.

Exercise 2: extend knee from stance 

You stand upright possibly behind a chair. You make sure the elastic band is approximately in the hollow of your knee. Now you are going to stretch your knee by moving from your toes to your heel. So you are going to unroll your whole foot. Make sure your upper body stays nice and straight to avoid compensation from the hip.

Exercise 3: extending the knee

You sit or lie in bed with your legs stretched out on the bed. You place a rolled up towel or pillow under the knee. You then try to stretch the knee as far as possible, pressing the back of the knee into the towel. You then slowly lower the foot back onto the bed. You repeat this exercise again preferably ten times. 

Exercise 4: extend and flex the knee in supine or seated position

The flexion and extension movement is an important movement of the knee. Often these knee movements are limited after injury or surgery. In the supine position, this movement is safe and easy to practice by sliding the foot along the ground.

physio fitaal physiotherapy
Richie Brewer

Physical therapist, sports rehabilitation

Evidence-based and measurable physical therapy. That's how we make care as efficient and targeted as possible. By collecting data during your rehabilitation, we know what you do, and therefore how you improve over time. In this way, together we ensure that you will soon be able to sport and move again without any complaints!