A healthy knee is a delicately balanced and, in some ways, quite an odd system of joints.
There are three separate joints at the knee;
The main joint, where the thigh bone rests on the shinbone.
The knee-cap, which rests on the thigh bone.
And the small joint between the shinbone and the top of the second, and much smaller, bone of the lower leg.
This amazing arrangement can easily be affected by problems in the lumbar spine.
For example, a vertebral joint gets stiff at the base of the spine.
This will alter the normal movement of one or both knees.
Now, the knee may well be able to cope with this, and you may not notice any symptoms, especially if you aren’t very active.
And there may be no symptoms in the stiff low back.
But often the knee begins to grumble when you take up some new activity (commonly, running), or you gain weight, or you get less fit.
So bear in mind that a knee that begins to niggle for no apparent reason may have a cause quite far away from the knee.
The low back is a frequent culprit here.