Alignment, Alignment, Alignment! Is as important as it gets for healthy knees.
Starting with the feet since they are the base and the grounding for the rest of the body. If the feet are not aligned and balanced then it translates misalignment in the knees, causing possible knee pain and deterioration. Two common alignment problems are when the feet either supinate or pronate causing stress on the knees. The feet roll inward or outward. putting stress on the inside or outside of the knee.
I tell my students the feet need attention too. We put shoes on in the morning and they don't come off until the evening. Yoga works the feet building flexibility and strength. In my Chair Yoga classes we work the feet. You can check out two poses for the feet in the "Yoga Minute" video series, #9 and #27.
The knee cartilage protects the knee joint. But without regular movement of the knee, the cartilage in the knee becomes dry and brittle causing damage. This happens with sedentary lifestyles. Including jobs that you're required to be seated at all day and then come home and sit the rest of the evening in front of the TV. When you move and exercise the knees move lubrication around the joints and the joints absorb nutrients helping to keep them healthy. In the "Yoga Minute" video series there are many poses that exercise the knees as well as the rest of the body.
If your seated at a desk all day you might want to consider a height adjustable standing desk from Varidesk. One of my students purchased one of these desks after I told them how being seated all day is unhealthy . She loves her standing desk.
Safety precautions for the knee: When doing some standing poses you want to keep the knee from coming forward past the knee. This can strain and injure the knee especially the ACL. Basically if you drop a plum line straight down from the knee it should line up with the heel. If you have pain or discomfort (tension) in the front or the insides and/or outsides of the knees while exercising you need to back out of the pose until the pain or discomfort disappears. If you have discomfort above the knee you should be okay since it's working the quadriceps muscles. When moving into deep bends, align the bending knee or knees over the ankles and inline with the second toe. The tendency is for the knee to be pulled in with the knee lining up on the inside of the toe causing possible injury.
When doing poses with straight legs you are prone to hyperextension in the knee, try to maintain a micro bend to help protect the knees especially if feeling any pain or discomfort. Also, with all poses especially with bent knees keep your weight evenly distributed between the four corners of your foot when coming out of the pose. I have experienced pain in my knee if I have more weight on the ball or heel of the foot. When I made the correction of having the weight distributed across the whole sole of the foot there was no more pain. A squat is different, you want the majority of the weight on the front of the heel when lifting your bodies weight.
There is much more that could be talked about when it comes to the knees. I hope this gives you some ideas how to keep your knees healthy and of course seek a doctor or physical therapist for more information.
Happy & Healthy,