Dashboard Knee: How Collisions Damage the Knee Joint

Sit in your car and look at how far your knee is from the dashboard. For most drivers it is a few inches. In a frontal collision your body moves forward until something stops it, and for the lower body that something is usually the dash or the steering column.

The classic mechanism

The knee is bent at roughly ninety degrees when you are seated. Impact drives the front of the shin bone backward relative to the thigh bone. The structure that resists exactly that motion is the posterior cruciate ligament, and this is why posterior cruciate injury is strongly associated with car crashes while the anterior cruciate is more associated with sports.

It is a quieter injury than an ACL tear. There is often no pop and no immediate giving way. Instead patients report a deep ache, a vague sense of instability going down stairs or downhill, and swelling that develops over the following day.

What else takes the hit

The kneecap is directly in the line of force. It can be bruised, and the cartilage on its underside can be damaged, producing pain at the front of the knee that shows up with stairs, squatting, and long periods seated with the knee bent.

The menisci are wedges of cartilage that cushion the joint. Axial loading combined with any rotation, which is common when a driver brakes hard with the foot planted and the body twists, can tear them. Meniscal pain tends to be felt along the joint line and often comes with catching, clicking, or a sense that the knee is not tracking cleanly.

Passengers with a foot braced against the floorboard and drivers standing on the brake pedal also transmit force up through the ankle and shin, which is why calf and ankle complaints often accompany knee complaints on the braking leg.

Why the knee gets missed

When someone arrives with neck pain, back pain, and a headache, the knee is fourth on the list. It also tends to hurt most with activities people naturally avoid in the first week. Then they return to normal life and discover the knee has not kept up.

A knee that is protected and unloaded also loses quadriceps strength quickly, and a weak quadriceps changes how the kneecap tracks. That turns an acute injury into a mechanical problem that persists after the original tissue has healed.

How we handle it

We test the ligaments individually, check meniscal signs, and assess how the kneecap tracks through range. We also look above and below, because hip and ankle mechanics drive a great deal of knee pain. Where imaging or surgical opinion is warranted, we say so and coordinate it.

If your knee hit the dash, have it looked at. Call (725) 255-7333. Henderson, southwest Las Vegas, and North Las Vegas.