How the Shoulder Gets Injured in a Car Accident

The shoulder is the most mobile joint in the body, and mobility is bought at the price of stability. It is held together largely by soft tissue rather than bone, which makes it well suited to reaching overhead and poorly suited to absorbing a sudden violent load. A collision delivers exactly that load.

The seatbelt is part of the story

In a frontal or offset impact, your body continues moving forward at the speed the car was traveling until something stops it. The shoulder harness is what stops the upper body, and it concentrates that entire deceleration across a narrow band of tissue running from the collarbone to the opposite hip. The belt does its job and keeps you in the vehicle. It also loads the shoulder complex harder than almost anything else in daily life.

This is why shoulder pain after a crash so often appears on the driver's left or the passenger's right, following the line of the belt.

What actually gets damaged

The rotator cuff is a group of four muscles whose tendons wrap the head of the humerus and hold it centered in a shallow socket. A sudden traction force can strain or tear these tendons, particularly the supraspinatus, which passes through a tight space beneath the acromion.

The labrum is a rim of cartilage that deepens the socket. Bracing against the steering wheel at the moment of impact drives the arm bone backward into that rim, and labral tears from this mechanism are common in people who saw the crash coming and tensed up.

The AC joint, where the collarbone meets the shoulder blade, is a small joint with a large job. Belt compression can sprain its supporting ligaments, producing pinpoint pain right on top of the shoulder that worsens when you reach across your body.

Why it often shows up late

In the hours after a collision your body is running on adrenaline and your attention is on the vehicles, the police report, and getting home. Soft tissue injury announces itself on the inflammatory timeline instead, which means stiffness and aching that build over the first day or two and are frequently worst on the second morning. Patients often tell us the shoulder felt fine at the scene.

A shoulder that is guarded and underused after an injury also stiffens quickly. Range of motion lost in the first few weeks is harder to recover later, which is the practical argument for getting evaluated early rather than waiting to see whether it settles.

How we approach it

We start with orthopedic testing to identify which structures are involved, because a cuff strain, a labral injury, and an AC sprain each respond to different work. Treatment addresses the joint mechanics of the shoulder along with the neck and upper back, since the shoulder blade rides on the rib cage and cannot move properly if the thoracic spine is locked down.

If you were in a collision and your shoulder is not moving the way it did before, call us at (725) 255-7333. We see patients in Henderson, southwest Las Vegas, and North Las Vegas.