Knee Airbags – Are They Effective? A Detailed Guide

Knee airbags are installed near the knees of the occupants in the front seats of a vehicle. They are effective in providing additional protection during a crash.

They serve as a complement to existing safety features such as front airbags.

Below, we will discuss the purpose of knee airbags, how they work, and the benefits of having them in a vehicle.

How Knee Airbags Work

Various sensors and other components are used to trigger knee airbag deployment. These include acceleration, rotation, proximity, and crash severity sensors.

The knee airbag is typically mounted under the dashboard or in the door trim on the side of the seat closest to the dashboard.

Dashboard - Knee airbags

Let’s discuss step by step how a knee airbag inflates and how it cushions the impact of a collision.

1. Sensor Detection:

The sensors send a signal to the airbag control module when a collision is detected. In addition, these sensors measure the speed and magnitude of the crash.

They also measure other factors, such as the angle of impact and the amount of deceleration.

This detection is necessary to determine the force required to deploy the airbag.

For instance, sensors detect a more severe collision. As a result, more airbags may be deployed to protect passengers.

Or if a frontal collision is detected, the knee airbag will get deployed to cushion the impact of the collision on the driver’s knees.

This sensor detection is different from other types of airbags. For instance, side airbags are triggered by a door-mounted sensor.

It detects the impact force through the door if a side collision occurs. But knee airbags are triggered by sensors mounted inside the car.

2. Igniter Activation:

The airbag control module is activated when the sensors detect a collision. It triggers the igniter.

The igniter is a chemical that produces gas when heated. This gas inflates the airbag cushioning material within milliseconds of the crash.

Once fully deployed, the airbag will provide a cushion to protect the driver’s knees.

However, this ignition process differs slightly from the one used for side or frontal airbags.

For instance, the airbag in side collisions relies on a pyrotechnic charge or explosive to inflate.

However, for knee airbags, the igniter and the gas it generates do the job.

The process is much faster than side airbag inflation. It provides more protection for the driver’s knees.

Additionally, knee airbags stay inflated for a longer period than other airbags.

This helps to provide an extra layer of protection against impacts. This reduces the chances of injury.

3. Gas Generation:

The activated igniter triggers a reaction that creates nitrogen gas. It is then used to inflate the airbag.

The knee airbag deploys quickly and rapidly inflates with pressurized nitrogen gas. This helps cushion the driver’s knees and reduce injury in a collision.

An igniter generates this gas triggered when sensors detect an impact on the vehicle.

The sensors are placed strategically around the car to detect any impacts or collisions.

4. Airbag Inflation:

When the igniter releases gas, it fills the nylon bag quickly to protect against impact.

The knee airbags deploy over your lower legs to protect them during an accident.

Knee airbags are much smaller and shorter than these other types of bags. But they still provide substantial protection.

Knee airbags are more effective at protecting the lower legs from direct impact than side curtain airbags.

In addition, they also help to push passengers away from the dashboard and the steering wheel. Thus, they minimize the potential for injury.

5. Protection Of Pelvis And Thighs:

Knee bags mainly work by protecting the lower legs. However, they can also help protect other areas, such as the pelvis and thighs.

The purpose is to help minimize the impact of a crash on these vulnerable areas. Serious injuries can occur when the pelvis and thighs are subjected to direct impact.

Knee airbags are designed to cushion the blow and absorb as much shock as possible.

They also stop the occupant’s body from hitting the cabin’s dashboard, steering wheel, and other objects.

This protection also reduces the strain on the upper body, such as the chest.

Reducing the force on the chest can help reduce the potential for injuries to the spine and internal organs.

Knee airbags are a great way to increase safety for drivers and passengers. They provide added protection during an accident.

They also deploy quickly and easily when needed to provide maximum safety benefits.

All cars nowadays should be equipped with this technology as it is proven to save lives in case of accidents.

Types Of Knee Airbags

Knee airbags come in different types, varying in effectiveness and deployment speed.

1. Single Stage Airbags:

Single-stage airbags are the most commonly seen type of knee airbags. They are designed to detect a collision and deploy within milliseconds.

The single-stage airbag will then quickly inflate, cushioning the lower legs from the dashboard area.

Single-stage Knee airbags

They are single-staged because they only need to deploy once, so they don’t require a dual-stage system.

Some advantages are that they can be cost-effective and are easy to install.

Single-stage airbags have a faster deployment speed than other types of airbags. They generally provide more protection.

2. Dual Stage Airbags:

Dual-stage airbags have a two-stage deployment system. They will first deploy quickly, then another layer is d, employed shortly after for added cushioning.

The second layer of protection protects the legs from more severe impacts during collisions.

This type of airbag is highly effective in providing an extra layer of safety.

But they tend to be more costly. In addition, they require complicated installation, making them less widely used than single-stage airbags.

Although more expensive, dual-stage airbags offer superior protection compared to single-stage airbags.

Safety Benefits Of Knee Airbags

Knee airbags help reduce fatalities and injuries in the event of a crash. Statistics show that knee airbags reduce the risk of injury from 7.9% to 7.4%.

This result, however, was not statistically significant. Knee airbags can help protect the legs from impacts and reduce the severity of leg injuries during a crash.

And with the addition of a knee airbag, the chances of lower extremity injuries are reduced by 5%.

Let’s discuss how knee airbags protect us:

1. Protect Knees And Lower Body:

Knee airbags deploy downward and outward from the dashboard to cushion the driver’s knees and lower body.

The airbag absorbs some of the impacts of a crash. In addition, it helps to keep your lower body in position during a collision.

Not only does the knee airbag helps to reduce leg injuries, but it also protects against any strain on your upper body and neck.

Some vehicles have knee airbags placed directly below your seat belt. This helps further to secure the driver’s lower body during a crash.

2. Work With Other Safety Features:

Knee airbags are just one part of an overall vehicle safety system. They work alongside seat belts, side curtain airbags, and other features.

Cushion the driver's knees and lower body -  Knee Airbags

Thus, they provide maximum protection for occupants during a crash. In many vehicles, knee airbags deploy along with the front airbag.

Together they provide additional cushioning for the driver’s legs and hips. This helps to reduce injury severity even further.

However, knee airbags are supplemental protection. They are not a replacement for seat belt use.

3. Prevent Specific Types Of Injury:

Knee airbags are most effective at preventing specific types of injuries, such as:

Tibial plateau fractures

Femoral fractures, and

Head injuries from contact with the dashboard

The airbag cushions the lower legs and hips and absorbs some of the impacts. This helps minimize injury severity in these specific areas.

With any airbag, some risks are associated with deployment. For example, an occupant’s legs may be too close to the dash and be injured by the airbag.

To reduce this risk, automakers usually install knee airbags in vehicles. Here occupants are seated far enough away from the dashboard for appropriate protection.

Limitations And Concerns

The knee airbag is effective in many situations, but some limitations exist. Let’s look at some of these.

1. Less Protection Against Serious Injuries:

It may not protect against serious injuries or fatalities. These result from an impact on the dashboard.

This can lead to serious injuries such as:

– Head trauma

– Spinal cord injury

– Abdominal trauma, and

– Upper extremity fractures.

These injuries are typically caused by the force of the dashboard compressing against the occupant’s body.

2. Risk Of Injury From Airbag Deployment:

Due to the nature of airbags, there are also certain concerns about airbag safety.

For example, occupants can suffer minor or severe injuries by airbag deployment due to improper seating positions or incorrect inflation rates.

Additionally, defective or counterfeit airbags may not deploy at all in case of an accident.

These situations can cause serious injury or even death. However, airbag technology has improved over time.

But it is important to understand the risks of airbag deployment before purchasing.

3. Danger Of Counterfeit Or Defective Airbags:

Another concern with airbag technology is the danger of counterfeit or defective airbags.

Counterfeit airbags are often made with inferior materials. As a result, they may not deploy correctly in an accident.

Counterfeit airbags

Defective airbags can also fail to deploy altogether. As a result, they can leave occupants unprotected in case of a collision.

Some counterfeit and defective airbags have even been found to cause harm. Thus, buying from a trusted dealer is important when purchasing an airbag-equipped vehicle.

4. Limitations Of Knee Airbags:

Knee airbags help protect the lower body in a collision. However, they have several limitations and do not offer protection against all types of injuries.

For example, knee airbags may be less effective in rollover accidents or side impacts.

They may also be ineffective if the occupant is not wearing a seatbelt or sitting properly.

Airbags can only deploy once and must be replaced after each deployment.

This could leave occupants unprotected in case of a second impact during the same incident.

Finally, knee airbags are a fairly new technology that may be more expensive than other vehicle safety features.

Maintenance And Replacement

When it comes to knee airbags, regular maintenance and inspection are key. Most manufacturers recommend servicing and replacing them every three years or 60,000 miles.

This can ensure they are in proper working condition. Let’s take a look at what to check when servicing and or replacing knee airbags:

1. Sensors Are Connected and Working:

Make sure all sensors connected to the knee airbag are working properly. Sensors are responsible for detecting an impact and triggering the airbag in time.

And once triggered, the airbag will deploy to protect the occupant. However, if sensors are not connected properly or working, the airbag may not work in times of need.

2. Inspect for Leaks and Damage:

Inspect all parts of the knee airbag for leaks and any signs of damage. If a leak is present, it could mean that the seal has failed or there is a crack in the airbag material.

In either case, the airbag must be replaced. Additionally, inspect that no wires or cables are damaged, and all connections are working properly.

3. Replace After Service Interval:

Knee airbags should be replaced after a certain service interval.

The recommended replacement time is usually between 10 to 15 years. This depends on the make and model of the vehicle.

To replace the airbag, first, remove it from the dashboard of the car or truck.

This process requires some tools and special safety equipment, so leaving it to a professional is best.

Once the airbag is removed, inspect the new one for any apparent defects.

Ensure all the wiring and hoses are connected properly and securely, then install them in place of the old ones.

4. Airbag Cushion Is Intact:

Check that the airbag cushion is not damaged or cracked. If it is, it will need to be replaced.

Some airbags may also have a pressure relief valve. It should be checked for proper functioning.

Finally, the mounting bolts and screws must be tightened securely to ensure proper installation.

Every three  years or 60,000 miles.

With any luck, the replacement will be successful. You’ll have a fully functioning knee airbag that can provide you with years of safe driving.

5. Hinges Are In Good Condition:

Inspect all hinges connected to the knee airbag. Hinges allow the knee airbag to deploy in a crash, so they must be in good condition.

Check for any signs of wear and tear or damage. They should be replaced immediately if worn, damaged, or otherwise compromised.

The process of replacing a knee airbag is relatively simple. But it does require the use of specialized tools.

For example, you’ll need to disconnect the battery and remove several components. Then you will gain access to the knee airbag.

Once these steps are complete, you can proceed with replacing the airbag. Make sure that all connections are secure before completing the installation.

And the associated costs can vary depending on the make and model of the vehicle.

Future Developments

Research and development efforts are continuing to improve knee airbag technology. The aim is to make them even safer, more reliable, and cost-effective.

One of the main focuses of current research is using smaller inflators in combination with advanced sensors.

This could lead to faster inflation times and more precise airbag deployment. In addition, new materials and manufacturing processes are being explored.

They can reduce costs and maximize the durability of the airbags. Developers are also looking into using artificial intelligence and machine learning algorithms.

They can help make better deployment decisions in case of a crash.

Knee airbag technology has come a long way since its introduction in automobiles.

Developers are now focusing on making the technology more cost-effective.

They are also expanding their capabilities to keep up with the ever-changing safety requirements of modern vehicles.

With these advances, knee airbags will remain a prominent part of automotive safety systems for many years.

Verdict – Should You Opt For Knee Airbags

Knee airbags offer a great deal of protection in the event of a crash. So it makes sense to invest in them.

They provide extra cushioning and stability for passengers during a collision. It can help reduce the risk of serious injuries.

Plus, they are relatively inexpensive and easy to install. So if you are looking for a way to upgrade your car’s safety system, then knee airbags are definitely worth considering.


Knee airbags are a great safety feature of modern automobiles. They protect the lower limbs, hips, and head during an accident.

They reduce the severity of injuries in these areas by cushioning the impact. In addition, they provide enough space between the occupant and the dashboard.

Airbags come with risks associated with their deployment. But automakers have taken steps to minimize these risks by installing knee airbags.

Their maintenance and replacement are important to ensure proper functioning.

Follow the manufacturer’s guidelines concerning airbags—this way; drivers can enjoy increased safety and security on the road.

With knee airbags, you can drive with confidence. In addition, you will know that your knees will be adequately protected in case of a crash.

Overall, these features are essential for a safe ride in any car.

About the author

David Englert is a 40-year-old mechanic specializing in airbags. With years of experience in the field, he has developed a deep understanding of the intricate workings of airbag systems. He is highly regarded in the industry for his expertise and attention to detail.

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