Knee Extension

Knee Extension

Knee Extension refers to the movement of straightening the knee joint, typically performed by the quadriceps muscles at the front of the thigh. It is a vital motion for activities like walking, standing, and climbing stairs. Knee extension exercises are often used in rehabilitation to restore strength and mobility after injury or surgery.

Knee Flexion and Extension: What Is It?

Important movements at the knee joint, such as knee flexion and extension, allow for various activities, including jogging, walking, and ascending stairs. The thigh bone (femur) and the shinbone (tibia) are joined by the knee joint, which is a hinge joint. There is also involvement of the patella, or kneecap, which articulates with the femur.

Flexion: It’s utilized to describe the bending motion that pulls the lower leg and thigh closer together by reducing their angle. When you lift your heel to your buttocks, your knee joint is flexed. Flexion is a basic motion used in sitting, kneeling, and leg lifting.

Extension: The opposed movement of flexion, likewise, is this. The angle between the thigh and the lower leg increases when the knee joint is stretched or straightened. When you flex your leg and then return it to its erect posture, you are extending your knee joint. Extension is needed for actions like jumping, kicking, and getting out of a seated position.

Both knee flexion and extension need coordinated motions of the muscles, ligaments, tendons, and other structures that surround the knee joint. The hamstrings, which are made up of the biceps femoris, semitendinosus, and semimembranosus muscles near the back of the leg, are the main muscles involved in knee flexion. When they contract, the knee is forced to flex. Knee flexion can be assisted by other muscles, such as the gastrocnemius (calf muscle).

The quadriceps muscles, which include the rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius, on the opposite together, are mainly responsible for knee extension. The front of the thigh contains the quadriceps muscles, which are in the role of straightening the knee joint. Knee extension is the result of these muscles contracting and applying stress to the patellar tendon, which joins the quadriceps muscles to the tibia.

For good joint function and normal lower limb movement, it is essential to maintain a balance between knee flexion and extension. Any injuries, weakness, or imbalances impacting these movements may result in a limited range of motion, decreased stability, or trouble carrying out daily tasks.

Knee Extension: What Is It?

The term “knee extension” means that the knee joint straightens out, increasing the angle between the lower leg and thigh. The quadriceps muscles at the front of the thigh, which are important in knee extension, are usually connected to this movement.

Walking, running, jumping, and kicking are just a few of the activities that need knee extension. Additionally, it is a crucial movement in lower body exercises including leg presses, pulses, and squats. Maintaining knee stability, avoiding injuries, and improving the functional range of motion all depend on strengthening the muscles used in knee extension, particularly the quadriceps.

Knee extension is regularly assessed in clinical settings to evaluate the quadriceps muscles’ strength and integrity as well as the knee joint’s general function. Knee flexion contracture, or the inability to fully extend the knee, can be a sign of several diseases or injuries, including neurological issues, joint stiffness, and muscular weakness.

It’s important to understand that proper technique and form are necessary for knee extension in order to prevent excessive stress on the joint and surrounding tissues. It is advised that you consult with a certified medical professional, such as a physiotherapist or sports medicine expert if you have specific questions or concerns regarding knee lengthening or rehabilitation.

Knee Extensors Muscles

The quadriceps, as they are commonly known, are the primary extensor muscles of the knee. Located on the front of the thigh, these muscles work to extend the knee joint. There are four separate muscles in the quadriceps group:

• Rectus Femoris: The Rectus Femoris is the only quadriceps muscle that crosses the hip and knee joints. It is situated in the center of the front of the thigh.
• Vastus Lateralis: The quadriceps group’s largest and most lateral muscle. Situated on the outside of the thigh, it facilitates the extension of the knee.
• Vastus Medialis: This inner thigh muscle assists in knee stability during knee extension by acting as a vastus medialis. Typically, it targets activities supposed to fix issues with patellar tracking.
• Vastus Intermedius: The vastus intermedius, which is situated deep between the vastus lateralis and vastus medialis, assists in knee extension and improves quadriceps strength in overall.

Together, these muscles provide the force required to extend the knee joint. It’s crucial to remember that the hamstrings, which are situated in the back of the thigh, also oppose the quadriceps. They give stability and control over the movements of the knee joint by acting as knee flexors and coordinating with the quadriceps.

Maintaining knee stability, preventing injuries, and maximizing functional range of motion all depend on the proper strengthening and rehabilitation of the knee extensors, which include the quadriceps. These muscles are the focus of exercises including squats, leg presses, pulse, and leg extensions, which enhance their power and endurance. For individual advice and exercise recommendations, it is always advised to speak with a doctor or certified fitness instructor.

Knee Extension Range of Motion

Knee flexion contracture, another name for knee extension, is usually considered to have a normal range of motion (ROM) of 0 degrees. Stated differently, the knee is at a 0-degree angle when it is fully extended. This indicates that the leg and thigh are parallel.

It’s crucial to remember, still that for some persons, even mild hypertension (over 0 degrees) stays within the normal range. Hyperextension is the ability of the knee joint to extend beyond the neutral 0-degree position. The knee may naturally extend a few degrees above 0 degrees in certain individuals without resulting in issues or discomfort.

However, a variety of conditions, including joint stiffness, inflammation, and muscular strain, can limit knee extension. When the knee cannot extend to 0 degrees or is not completely stretched, flexion contracture of the knee develops. Conditions like arthritis, ligament damage, muscle imbalances, and post-operative problems can all result in knee flexion contracture.

A goniometer, an experienced instrument for measuring joint angles, can be used in clinical settings to evaluate knee extension range of motion. This measurement helps medical practitioners in determining the knee joint’s range of motion and flexibility as well as any restrictions or abnormalities.

It is advised that you consult with a physician, such as an orthopedist or physical therapist if you have issues moving your knees or are worried about your knee range of motion. Depending on your particular requirements, they can offer a comprehensive evaluation, diagnosis, and suitable treatment or rehabilitation plans.

To determine your knee extension range of motion, follow these steps:

• Preparation of the patient: Ask the patient to lie with their legs extended on a level surface, like a bed or examination table.
• Position: Ensure that the knee is fully extended and the patient’s leg is relaxed and straight. While the examination is being performed, the patient should feel at ease and relaxed.
• Beginning position: To stabilize the patient’s knee, place one hand behind it and place the other over the ankle.
• Active range of motion (AROM): While extending the leg, instruct the patient to actively extend the knee. Instruct the use of gentle, fluid motions for these activities.
• Measure and observe: Watch how the patient’s knee joint moves while it is extended. Recognize the patient’s limitations, pain, and discomfort. Determine the extent of knee extension using visual clues.
• Measurement of the goniometer (optional): To gain a more precise measurement for knee extension, if one is available, you can use a goniometer, a specialized instrument for measuring joint angles. Position the goniometer’s moving arm parallel to the lower leg’s long axis (tibia) and its fixed arm parallel to the femur’s (thigh) long axis. Measure the angle created when the patient extends their knee after aligning the goniometer’s center with the knee joint’s axis.
• Repeat the technique: To verify clarity and observe any irregularities in the patient’s movement, repeat the procedure a few times.
• Document findings: Include measurements and findings in the patient’s examination notes or medical file.

Any restrictions, discomfort, or abnormalities observed during the knee extension test should be noted. It is crucial to keep in mind that the range of motion of knee extension should be evaluated by a physician, physical therapist, or orthopedist. To properly evaluate the knee joint and interpret the results, they require the requisite skills and knowledge.

Knee Extension Special Test

In clinical settings, knee sprains and associated conditions are assessed using several specific tests. Below are a few examples:

Active test for the knee joint:

This test evaluates a person’s capacity for active knee joint extension. With their legs extended wide, the person tries to straighten their knee as much as they can while lying on their back. By extending the knee using a goniometer, the researcher examines and calculates the angle achieved.

Knee extension test in a passive manner:

During this examination, the examiner checks the subject’s leg and, when the subject relaxes, softly extends the knee joint. The examiner monitors the range of motion gained and looks for any restrictions or pain when passively extending the knee.

Ober’s test:

The purpose of this test is to evaluate the iliotibial (IT) band’s tightness or contracture. A man with his legs bent is lying on his side. Lifting the leg, the examiner allows it to hang loosely off the table. After that, they gradually bring their legs down to the table. If the leg remains upright and does not touch the table, it is a sign of a tight IT band.

Ely’s testing:

The rectus femoris muscle’s tension or contraction is assessed by this test. The examiner brings the heel to the buttock by bending his knee while the subject is lying prone. A person has rectus femoris if, when the knee is bent, the hip elevates off the table.

Thomas’s test:

This test helps in evaluating hip flexor tension, which may have an impact on knee extension. On the edge of a table, a man is lying on his back with one knee pulled up to his chest. With the knee outstretched, one leg hangs over the table. A hip flexor strain is indicated if the extended leg lifts off the table or is unable to lie down.

To evaluate knee extension, identify possible restrictions, and notice specific conditions or muscular imbalances, these tests are usually combined with other clinical evaluations. Health professionals who have received the necessary training for performing and appropriately interpreting these tests, such as orthopedists or physical therapists, are usually carrying out procedures properly.

Manual Muscle Testing For Knee Extension

One method for evaluating the strength and functionality of specific muscles surrounding the knee joint is manual muscle testing. To assess a muscle group’s strength, resistance is applied to the group’s movement. The following is an introduction to manual muscle testing for the main knee muscle groups:

Muscle testing

Quadriceps muscle

Position of the patient

The patient must be able to sit comfortably.
To perform all of the tasks without any limitations, patients must dress comfortably.

The patient should sit for a brief period to evaluate grades 3 through 5.

For the test, grades 0–2 The most suitable position for the patient is side-lying.

Position of the Therapist

Fixing the femur on the side being evaluated requires the therapist to kneel close to the patient.

The lower limb should be supported by the therapist using movement when the patient is side-lying.

What is the test procedure?

Thigh stabilization: To stabilize the patient’s thigh, the therapist should put one hand below it.

The therapist’s second hand should be placed on the patient’s lower leg, somewhat above the ankle.

It is recommended that the therapist ask the patient to push their foot toward the ceiling in order to straighten their knee.

Knee extension is done by the patient himself.

Give the distal tibia and fibula resistance force in the opposite direction of knee extensions to evaluate grades 4 and 5.

The therapist should apply pressure on the lower leg to prevent this movement.

Increase resistance: Until the therapist determines that the patient is doing their best effort, gradually increase the resistance.

Grade the strength: The knee extensor strength should be assessed by the therapist using the previously mentioned criteria, with a range of 0 to 5.
Here is the grading method:

• Grade 0: No feeling of contraction
• Grade 1: There is no movement, only a noticeable flicker or contraction trace.
• Grade 2: Motion that is gravity-free, such as horizontal
• Grade 3: The motion must overcome gravity without becoming resistant.
• Grade 4: There should be mild to moderate resistance to the movement as it goes against gravity.
• Grade 5: Excellent strength in the face of complete resistance

Make sure you use the correct technique: Make that the patient is solely using their knee extensors and not compensatory through using their back or hip extensors.

Verify that there is no pain or discomfort for the patient during the test by checking for it.

Precaution

Check for contraindications: The therapist should look for any conditions that could prevent the knee manual muscle test from being performed, such as recent surgery, an acute injury, or inflammation in the knee joint.

Warm-up: Before doing the test, the therapist should make sure the patient’s muscles are adequately warmed up to avoid any injuries.

Proper positioning: To avoid putting unnecessary strain on the knee joint, the patient should be in a comfortable position with enough support.

Resistance should be increased gradually by the therapist to avoid any injury-causing rapid movements throughout the test.

Patient communication: To make sure the patient is not in any pain or discomfort during the test, the therapist should keep in touch with them.

Safety precautions: To avoid any injuries or accidents during the test, the therapist should take the required safety measures, such as utilizing the appropriate tools and making sure the area is secure.

Knee Extension Exercise

Many exercises are available to improve knee extension and strengthen the quadriceps and other muscles involved in knee extension. The following exercises for knee extension are usually suggested:

Knee Extension

How to Do It:

Sit in a chair or on a platform with your hips and knees at a 90-degree angle. To help you increase your range of motion, roll up a towel and place it under one knee. Then, straighten out the leg by using the towel below it. Squeeze the quad as much as you can, holding for two to three seconds before putting it back to rest. Repeat for three sets of ten reps on each side.

Straight leg lift:

With one leg bent and the other extended, lie on your back. Lift the extended leg straight off the ground by contracting its quadriceps. Lower it once more after holding it for a few seconds. Repeat a few times, then change legs.

Quad Sets:

Place your feet in front of you and sit or lie down. Press the back of your knee onto the floor or another surface to contract your quads while maintaining a straight leg. Do this for several sets.

Box Squat with Load

The knee joint will be functionally straightened with this movement.  Focusing on slowing down this motion to guarantee appropriate muscle fiber recruitment.

How to Do It:

Stand in front of a box and hold a dumbbell or kettlebell in front of your chest to start.
Completely lower the box until you are seated on it. Hold for a few seconds, then stand up again, contracting your quadriceps as you go.
For three sets of ten reps, repeat.

Step Up

Another useful exercise for knee extension is the step-up. To make it more difficult, use a weight and hold it up to your chest, just like in the last exercise.

How to Do It:

To perform this exercise, locate a box or other stable surface, place one foot up on it, step up by firmly squeezing the quadriceps to straighten out the front knee, and then slowly lower the lower leg back to the floor. Repeat three sets of ten repetitions on each side.

Terminal Knee Extension with Bands

The goal of this exercise is to improve knee extension’s terminal end, or the final few degrees before the joint fully straightens. Build a thicker band or move farther away from the anchor point to increase the effect.

How to Do It:

Secure a lengthy loop band to a post or other solid object. Just behind your knee, hook your foot into the loop.
Step back until the band is tense. Straighten the knee against the resistance after bending it to relieve part of the stress.
Do this for three sets of ten reps on each side.

Short Arc Quads:

While lying on your back, place a towel or foam roller beneath your knees. Maintaining a flat thigh, slowly straighten your knees as you raise your legs off the towel or roller. Hold the extended posture for a little while before lowering it again, repeating several times.

Wall slide:

Place your back against a wall and place your feet shoulder-width apart. Slide up the wall into a partial squat while maintaining your knees in line with your toes. Repeat a few times.

A stationary bicycle

Strengthening the quadriceps and facilitating knee extension are two benefits of stationary bike riding. Focus on fully extending your knees with each pedal stroke and begin with a resistance level that is comfortable for you.

It is crucial to begin these exercises at a level by your present degree of strength and flexibility. Speaking with a healthcare professional, such as a physiotherapist, is advised if you have knee conditions or issues. They can offer individualized advice, identify the best exercises, and provide the correct form and technique to stop additional injury.

As you advance in the exercises, progressively raise the level of effort or difficulty while paying attention to your body. For best results and to lower the chance of damage, consistency and good form are essential.

FAQs

References:

• Patel, D. (2023c, July 11). Knee flexion and Extension – movement, ROM, function, exercise. Samarpan Physiotherapy Clinic. https://samarpanphysioclinic.com/knee-flexion-and-extension/
• Patel, D. (2023b, May 27). Manual muscle testing of knee – quadriceps, hamstring muscles. Samarpan Physiotherapy Clinic. https://samarpanphysioclinic.com/manual-muscle-testing-of-knee/
• CSCS, C. R. (2023, August 16). A physical therapist shares 4 exercises to strengthen knee extension. Men’s Health. https://www.menshealth.com/fitness/a44702238/knee-extension-exercises/