Go to the bottom of the trousers and open the Velcro tab

Once opened you should have access to the ankle zip

Once open this is what you should see

Open the hidden Velcro strip - this is sewn under the zip on the same side as the velcro tab

Once opened you can access inside the trousers, and feel for the armor pocket. Pull the pocket down and out of the opening

Open the Velcro tab on the pocket and remove the knee armour!