Knee Flexion

Knee Flexion

Knee Flexion refers to the bending movement of the knee joint, where the angle between the thigh and the lower leg decreases. It involves muscles like the hamstrings, gastrocnemius, and popliteus. Knee flexion is essential for activities like walking, running, and squatting.

Knee Flexion and Extension: What Is It?

Basic motions 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, a hinge joint. The patella, or kneecap, which articulates with the femur, is also involved.

Flexion: Is used to describe the bending motion that puts the lower leg and thigh closer together by reducing their angle. Your knee joint is flexed as you raise your heel to your buttocks. One of the basic movements utilized in sitting, kneeling, and leg raising is flexion.

Extension: The opposing movement of flexion, however, is this. The angle between the thigh and the lower leg is increased when the knee joint is stretched or straightened. Your knee joint is being extended when you bring your leg back to its erect position after flexing it. Extension is necessary for actions like jumping, kicking, and getting out of a sitting posture.

Coordinated movements of the muscles, ligaments, tendons, and other tissues surrounding the knee joint are required for both knee flexion and extension. The hamstrings, which are made up of the biceps femoris, semitendinosus, and semimembranosus muscles near the rear of the leg, are the main muscles involved in knee flexion. They require the knee to flex as they contract. Knee flexion is also helped 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 the moment, are mainly responsible for knee extension. The front of the thigh contains the quadriceps muscles, which are responsible for straightening the knee joint. Knee extension is the consequence of these muscles contracting and applying stress to the patellar tendon, which joins the quadriceps muscles to the tibia.

For good joint function and general lower limb mobility, it is essential to maintain a balance between knee flexion and extension. Any injuries, weakness, or imbalances impacting these motions may result in reduced range of motion, decreased stability, or difficulty carrying out daily tasks.

Knee Flexion: What Is It?

Knee flexion is the term for the bending or movement of the knee joint that causes the angle between the tibia (shin) and femur (femur) to decrease. Walking, jogging, kneeling, and sitting are all performed possible by this crucial knee movement.

Knee flexion is bending the knee joint to move the heel closer to the buttocks when standing. The hamstrings near the rear of the thigh are one of the muscles that control this movement. As they contract to draw the lower leg up towards the buttocks, the hamstrings are responsible for bending the knee. In daily life and for a variety of useful actions, the knee must be bent. This gives the lower limb a great deal of range of motion, which helps the body move forward while walking and running. Additionally, it helps people to bend, squat, kneel, and climb stairs for example.

Knee flexion measurement is required for evaluating joint function and identifying any kind of restrictions or abnormalities. In order to assess the range of motion during knee flexion, doctors frequently utilize a goniometer, a tool that measures joint angles. This information may be used to diagnose conditions, create rehabilitation plans, and track the healing process following knee-related operations or injuries.

Knee Flexor Muscles

A group of muscles at the back of the thigh called the knee flexors are crucial for knee flexion. Together, these muscles allow the knee joint to bend and raise the leg toward the buttocks. These are the primary knee flexors:

• Hamstrings: three-muscle groups situated on the lower part of the thigh. Some of them are:
• Biceps femoris: Located on the outside of the thigh, this muscle contains two heads: a long head and a short head. Inside the thigh is the muscle known as the semitendinosus. Additionally, the inside thigh contains the semimembranosus muscle.
• Gastrocnemius: The calf is formed by the gastrocnemius muscle, a big muscle in the back of the lower leg. When the foot is off the ground (when walking or running), it helps bend the knee by crossing the knee joint.
• Popliteus: A little muscle behind the knee joint is called the popliteus. By laterally rotating the tibia to expand the knee joint before flexion, it helps start knee flexion.

The strength and flexibility of these muscles are necessary for a variety of tasks, including walking, running, and bending. They assist in flexing the knee joint. To maintain knee health and avoid damage, these muscles must be properly maintained and flexible.

Flexion range of motion of the knee

Range of motion (ROM) for knee flexion is the degree of flexion or movement that the knee joint can do when flexed. It shows the angle at which the knee may be bent and is expressed in degrees.

Adults’ normal knee flexion range of motion can be regarded as 135 to 145 degrees. As a result, the heel may approach or touch the buttock when the knee joint is flexed, bringing the lower leg closer.

The actual range of motion, however, can vary from person to person based on factors including age, physical condition, past injuries, and different anatomical variances. Based on these variables, certain persons may have varying degrees of knee flexion.

Evaluation of knee flexion range of motion is crucial for the diagnosis and follow-up of a number of conditions, including surgical rehabilitation, ligament damage, muscle strains, and osteoarthritis of the knee. A goniometer, a joint angle instrument, is frequently utilized by doctors to precisely measure the range of motion in knee flexion. This assessment informs therapy and rehabilitation plans by assisting in determining the degree of restrictions or abnormalities.

To measure the range of motion of your knee flexion:

• Set up the space: look for a calm, open spot where the individual may sit or lie down without discomfort. Make sure there is enough space for your legs to move freely.
• Clearly explain the instructions: To the individual whose knee motion you are assessing, describe the procedure. As you gently move their leg, let them know that they should notify you if they feel any pain or discomfort.
• Starting position: Request that the individual sit on a sturdy surface with their legs out in front of them or lie on their back.
• Ankle Support: While evaluating mobility, place one hand behind the person’s ankle to support and stabilize the leg.
• Extension assessment (zero degrees): Make sure the knee is entirely straight or slightly bent when the person’s leg is fully extended. The knee should ideally be completely extended (straight), with no visible bend.
• Flexion assessment: Bring the heel to the buttock by slowly and carefully bending the person’s knee. Motivate them to relax and allow their legs to move freely. Until you can no longer bend the knee comfortably, keep an eye on the degree of flexion.
• Measuring range of motion: One specific tool that may be used to assess range of motion is a goniometer. Align the goniometer’s fixed arm with the hip joint by placing it on the subject’s thigh. Place the moving hand along the leg so that it is in line with the knee joint. At the point where the two arms of the goniometer connect, read it’s a measuring instrument.
• Note the measurement: Indicate the degree of bending attained by marking the measurement on the goniometer.
• Check for pain or discomfort: During the range-of-motion evaluation, inquire whether the patient is experiencing any knee pain, discomfort, or resistance.

Stop the movement and refrain from pushing over a comfortable range if this occurs. For an appropriate assessment and advice, it is advised that anybody with a history of knee problems or a recent accident speak with a physician.

Knee Flexion Special Test

When measuring knee flexion, medical practitioners may use several specialized tests to evaluate specific problems or injuries. Here are a few popular specific knee flexion tests:

Test of passive knee flexion:

The patient is placed in the supine posture for this examination. In an attempt to achieve the maximum range of motion, the examiner carefully flexes the patient’s knee. The test detects any restrictions and assists in determining the patient’s passive knee flexion range.

Heel-to-buttock testing:

While the patient is in a prone position, the examiner attempts to bring the patient’s heel to the buttock by bending the knee. The test evaluates the capacity for complete knee flexion and can detect any restrictions or discomfort during motion.

Test for Gastrocnemius Length:

Sometimes knee flexion can be restricted by the gastrocnemius muscle, which is a calf muscle. The patient stands with their hands on a wall, one leg straight back, the heel on the ground, and the other leg forward, with the knee bent slightly, for this test. The patient will struggle to maintain complete ground contact with the heel when the leg is extended if the gastrocnemius muscle is not very flexible.

Ober’s test:

This test evaluates the iliotibial (IT) band’s flexibility, which has an impact on knee flexion. The patient is on his side with his upper body flexed at the hip and knee and his lower leg outstretched. Once the patient’s pelvis has been stabilized, the examiner carefully extends and abducts the lower leg. The leg remains up when the IT band is tight, suggesting a restricted range of motion.

Thomas’s test:

Thomas’ test may provide information on knee flexion even if its primary purpose is to evaluate hip flexion. One leg hangs on the table while the patient rests on it with the other knee bent to the chest. Limited knee flexion may also be indicated if the hanging leg’s hip flexors or quadriceps are too tight to allow for complete knee flexion.

Goniometry:

A measuring method called goniometry is used to evaluate a joint’s range of motion, including knee flexion.
The knee flexion angle is frequently measured with a goniometer, a specialized instrument.
The subject’s legs are straight as they rest on a level surface. After focusing the goniometer at the knee joint, the subject is instructed to bend their knee as much as they can.
The knee joint’s angle is measured and noted.
Generally speaking, a knee’s natural flexion is between 135 and 155 degrees.

Test of Sitting and Reaching:

The sit and reach test may provide an indirect indication of the degree of knee flexion, even though its primary purpose is to evaluate thigh and lower back flexibility.
Your legs should be out in front of you while you sit on the floor.
On the ground between your feet, in front of your heels, place a ruler or tape measure.
Slide your arms along the measuring tape or ruler as far forward as you can.
The flexibility of the hamstrings, which affects knee flexion, is indicated by the distance above the toes.
A broad picture of the lower limbs’ general flexibility, including knee flexion, is given by this test.

It is necessary to remember that healthcare professionals with the required education and experience commonly perform these examinations. They assist in the identification of particular conditions or injuries involving knee flexion by providing useful information.

Manual Muscle Testing For Knee Flexion

A technique called manual muscle testing of the knee is used to evaluate the function and strength of certain muscles around the knee joint. It measures the strength of a muscle group by introducing resistance to its movement. A general reference to manual muscle testing for the main knee muscle groups is provided here:

Muscle testing

The hamstring, sartorius, gastrocnemius, plantaris, gracilis, and popliteus muscles are all part of the knee flexors. The primary knee flexors are the hamstring muscle group.

• Biceps femoris
• Semitendinosus
• Semimembranosus

Position of the patient

The position of the patient must be comfortable.
Patients are expected to dress comfortably so that they can move freely and completely.
To evaluate students in grades 3 through 5 Patients should lie with their knees extended and on their stomachs.

The patient should be side-lying with their knee extended to evaluate grades 0–2.

Position of the Therapist

When the patient is in the prone position, the therapist must be positioned by the patient’s side.

The patient must be side-lying, and the therapist must stand behind them, supporting the lower leg with movement as needed.

What is the test procedure?

In the range that is available, the patient performs the knee flexion themself.

Use the distal tibia and fibula to apply resistance force in the opposite direction of knee flexion to evaluate grades 4–5.

Following that, the therapist should assign a grade to the knee flexor strength based on the previously mentioned criteria. Grade 0 would indicate no sign of muscular contraction, while grade 5 would indicate the ability to completely flex the knee against maximal resistance.
The following is how grades are assigned:

• Grade 0: No contraction was detected
• Grade 1: There is no movement but a noticeable flicker or contraction trace.
• Grade 2: Movement that is gravity-free (horizontal)
• Grade 3: The motion should be resisting gravity without experiencing any resistance.
• Grade 4: There should be mild to moderate resistance and the movement should be opposed to gravity.
• Grade 5: Excellent strength in the face of total resistance

The therapist must make sure the patient is performing the action only with their knee flexors and not compensating with their hip flexors or back muscles. During the test, the therapist should also make sure the patient is not in any pain or discomfort.

All things considered, manual knee flexor muscle testing can provide important data on a patient’s muscle strength and function, which can direct therapy and recovery strategies.

Knee Flexion Exercise

For better knee flexion, it is essential to perform exercises that focus on the hamstrings and calf muscles. The following exercises can improve knee flexion:

Stretching the hamstrings:

Do hamstring stretches to gain more flexibility and range of motion. For hamstring stretches, you can try sitting, standing, or lying down. Each leg should be stretched many times, with each hold lasting 20 to 30 seconds.

Sliding walls:

Place your back against the wall and stand with your feet hip-width apart. Maintaining a bent knee and toe alignment, slowly down the wall into a squat position. Go as low as you can while maintaining a 90-degree angle at your knees. After holding for a few seconds, push through your heel to stand again. Do 10–15 repetitions in two or three sets.

Calves:

Proper knee flexion requires strong calves. Maintain a shoulder-width distance between your feet and raise yourself as high as you can on your toes. Reduce your heels gradually. Leg lifts can be done with both legs at the same time, or with only one leg for more difficulty. Doing two to three sets of ten to fifteen repetitions is the aim.

Knee bend when seated:

With your feet flat on the floor, take a seat on a chair or bench.
As you gently lift one leg off the floor and bring the heel to your buttocks, bend the knee as much as you can.
Hold this stance for a few seconds, then slowly lower your legs back to the floor.

To finish the exercise, use the opposite leg.
Aim for 10 to 15 repetitions per leg.

Hamstring curls standing:

If necessary, use a chair or wall for support and place your feet shoulder-width apart.
Bring your heel to your butt by bending the opposing knee as if you tried to kick it.
Hold this position for a few while, then slowly lower your legs back to the floor.

Do the same with the opposite leg.
As you gain strength, progressively increase the number of repetitions you do on each leg from 10 to 15.

Knee Flexion in Prone Position:

Place your legs straight and lie face down on a mat or bed.
As you bend the second knee and bring your heel to your glutes, keep your thigh on the surface.

After maintaining the pose for a few while, slowly lower your legs again.
On the opposite leg, do the same technique.
Perform 10–15 reps on each leg.

Leg Extensions While Seated:

Your feet should be level with the floor and your back should be straight when you sit.
Lift one leg in front of you and try to keep the knee as straight as possible.
Return your legs to the extended position with carefully after a few seconds.

Continue with the opposite leg.

Knee flexion stretch while seated:

• With your feet on the ground, take a seat on the edge of a chair or bench.
• Keep the heel of one leg on the ground while you extend it out in front of you.
• Bring your heel closer to your glutes, bend your knee, and slowly glide your leg back towards you.
• After 15 to 30 seconds of holding the extended position, softly touch the front of the knee and thigh.
• Release the strain gradually and return the leg to the starting position.
• With the opposite leg, repeat the stretch.
• Aim for two to three repetitions of each leg.

Do not forget to begin with a weight or resistance level that challenges you while maintaining the correct technique.

Heel Slides

To assist bring the knee into more flexion, wrap a towel or strap around the ankle or foot if your range of motion is becoming better but you still need to advance. Repeat ten to fifteen times, two to three times a day, daily, or as tolerated.

Kneeling Progression

A kneeling progression is a little more complex. These can assist reduce the knee to a kneeling posture in addition to increasing knee flexion.

As far as it is comfortable, begin with quadruped rock backs, rocking your butt back to your heels. Advance to a half-kneeling rock back, which will bias one knee, and then to a tall kneeling rock back, where you will go from a tall kneeling posture to a low kneeling position. Sit your butt as close to your heel as you can while still in a half-kneeling stance.

Benefits Of Knee Flexion Exercises

• Knee flexion is essential for daily tasks, including sitting, walking, crouching, and climbing stairs.
• Improved Balance and Stability: A strong, flexible knee flexion lowers the chance of falls by promoting improved balance and stability.
• Increased Mobility: For general mobility and an active lifestyle, it is essential to maintain a healthy range of knee flexion.
• Functional Independence: People may continue to be independent and carry out daily tasks without trouble when their knee joint is healthy and has enough flexibility.
• One of the most important aspects of rehabilitation following knee surgery, such as total knee replacement (TKR) or other knee operations, is knee flexion.
• Regaining Range of Motion: Functional rehabilitation requires the ability to regain and sustain a complete range of motion, which is achieved with exercises that focus on knee flexion.
• Reducing Stiffness: Exercises that encourage knee flexion and early mobilization can assist improve joint function and lessen stiffness.
• Pain management: To reduce knee pain and enhance general knee health, strengthen the muscles surrounding the knee, especially those engaged in flexion.

• Particular Advantages:
• Muscle Strength: The hamstring muscles, which are in the role of bending the knee, are strengthened via knee flexion exercises.
• Better Muscle Function: The length-tension relationship of muscle fibers may be improved by larger knee flexion angles, which enables them to produce force more efficiently.
• Improved Performance: For a variety of physical activities, such as sports and exercise, a good range of knee flexion is essential.
• Decreased Risk of Injury: The risk of knee injuries can be decreased by maintaining and strengthening knee flexion flexibility.
• Better walking: A regular and effective walking pattern depends on adequate knee flexion.

FAQs

References:

• Patel, D. (2023w, July 11). Knee flexion and Extension – movement, ROM, function, exercise. Samarpan Physiotherapy Clinic. https://samarpanphysioclinic.com/knee-flexion-and-extension/
• Patel, D. (2023h, May 27). Manual muscle testing of the knee – quadriceps, hamstring muscles. Samarpan Physiotherapy Clinic. https://samarpanphysioclinic.com/manual-muscle-testing-of-knee/
• Comella, T. (2023, December 13). Improving knee flexion range of motion. E3 Rehab. https://e3rehab.com/knee-flexion/