What is actually happening when a knee feels like it is giving way?
Combination of muscle weakness, cartilage tears, and/or ligament instability, allowing the knee to give way. (See below for a list of possible ligaments involved.)
Do people have falls from this instability?
Yes, people fall, and may start using an assistive device such as a cane, walker (frame), crutches, or wheel chair to prevent falls.
Can someone who doesn't have a prosthetic in the knee experience instability?
Yes, if the ligaments of the knee or torn or stretched the person may have instability, giving way, and/or pain which may lead to falls.
Scenarios in an intact knee may include injury or rupture to the following tendons, ACL (anterior cruciate ligament), PCL (posterior cruciate ligament), MCL (medical collateral ligament), LCL (lateral collateral ligament), and patellar tendon. A cartilage tear can also cause knee instability.
Depending on the prosthesis you have, injury or rupture to any of the above ligaments can cause instability. Here is an article about the different types of knee implants.
Multiple types of knee implants are available for different types of knee replacement, types of patients, and preferences of surgeons. Total knee replacement implants replace your arthritic or damaged knee joint eliminating bearing surfaces that are causing you pain. Based upon your age and...
bonesmart.org