Knee Walker Quick Release Device Failures Expert Article

This article discusses the use of quick release mechanisms on rollators, knee scooters/walkers, and other mobility aids, with an introduction to quick release operation and associated failures.

Knee Walker Expert Witness

Quick Releases Failures on Rollators, Knee Walkers, and Other Mobility Aids

A quick release (QR) is a device found on thousands medical walking aids, such as rollators, sold in the United States each year. Its function is to fix the foldable steering column in the upright position. The benefit of this feature is tool-free folding of the device for shipping and storage. The device consists of a threaded rod with a lever-actuated cam on one end. The tension that allows the quick release to safely stay closed is provided by the actual stretch of the threaded shaft. When the device is not adjusted properly failures can be caused by too little or too much tension:

  • If the QR is too loose it can come open while using, leading to the potential of a sudden loss of both the user’s support from the handlebars and the inability to control direction. Either of these situations can lead to a loss of control and a fall.
  • If the QR is too tight the shaft can be permanently elongated, preventing proper closing tension from being achieved. This too can lead to the QR opening unexpectedly.

Figure:1 Anatomy of Quick Release Mechanism

Avoiding Quick Release Failures

The adjusting nut opposite the lever-actuated cam must be spun such that clamping force is generated that will stretch the QR shaft by a very specific distance (usually less than 1 millimeter). To a first-time user of these devices, this information should come from an informed medical device shop employee or other trained professional. Proper operation of a quick release seems straightforward, but instruction and practice may be necessary to ensure that a QR is closed safely and consistently.

Initial Setup Difficulties

The initial adjustment can be done by an employee at the location where the rollators are sold and/or rented. The training and supervision of these employees is critical to the safe and secure adjustment of the quick release. In a case involving a claim of improper rollator setup, it can be valuable to inspect training documentation for personnel who assemble, adjust, and sell or rent these devices.

Bicycle Component Crossover

The rollator image identifies the components sourced from the bicycle industry. Hand-operated brake levers pull standard bicycle brake cables through brake housings. The quick release device that allows tool-free height adjustment of the handlebar is the same as a bicycle seat post clamp. The hinge at the bottom of the steering stem is the same design commonly found on folding bicycles.

Figure 2: Bicycle Components Used on Knee Walkers

Alternative Designs for Rollator Steering

In many occasions the only time the quick release is operated is after shipping from the factory or distributor and before sale or rent. Because of this, one alternative would be for the quick release to be eliminated, and a clamp that requires a hex wrench to be substituted. In that way, the adjustment could be made at the time of sale with less chance of later improper adjustment by untrained users.

Rollator Component Failure Investigations

Our experts are regularly retained in rollator design, assembly, maintenance, and repair cases involving falls, collisions, traumatic brain injuries, and deaths that are associated with the use and misuse of these devices. The scope of our investigations can encompass user action, instruction, assembly, design, inspection, and maintenance.

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