As we all know, there are many changes that occur with aging. Overall posture starts to change. We aren't as stable in the upright position as we once were. Around the knee the
quadriceps muscle strength is less. Aging often brings arthritic changes that affect the knee.
At the same time there is a reduced amount of joint position sense. Position sense (knowing where the joint is in space) is called proprioception. Scientists aren't sure what comes first, the arthritis or the decreased proprioception.
It's even possible that arthritic and disc changes in the neck can lead to changes in knee proprioception. One study has shown that patients with pressure on the spinal cord
in the neck have altered knee proprioception. Another study confirms that patients with arthritis in one knee have decreased joint position sense in the other knee.
More study is needed to sort these factors out. In the meantime, make an appointment with your family doctor. It might be a good idea to rule out anything more serious going on
and get a baseline. You may just need a conditioning or strengthening program.