If the shaft of your strut is showing any signs of rust, as per the photo, the effectiveness of your strut will be affected.

If  your strut is showing any signs of fluid having leaked and caused debris ,dust or dirt to accumulate, as per the photo, the effectiveness of your strut will be affected.

If the shaft and/or the housing of the strut is damaged, as per the photos,  the effectiveness of your strut may be affected.This image is also showing severe rust damage.

Due to wear, damage or other reasons, the strut components are binding, interfering with each other and creating a “mechanically painful”   (and likely causing an incorrectly functioning strut) sound.

This one might be more obvious. If a strut has completely failed, then its function to assist in lifting or control closing, is gone and heavy components moving in an uncontrolled manner can cause personal injury. In this instance, look for any/all of the above listed failure points to determine the cause.

If none of the above is the cause, but the strut is not functioning correctly, it may just need to be re-gassed, that is, the gas inside the strut has , over time, leaked to such an extent, it no longer functions, so it may just be necessary to re-gas the strut to bring it back to full function. Alan, your friendly re- gas expert, will be able to advise you on this.