The knee is essentially a hinge joint. Itís primarily built to allow bending and straightening (flexion and extension). This is a simple function. If that were all it had to do, it could be a very strong joint, resistant to all types of injuries. Think of the hinges on your door Ė strong and useful.
According to www.arthroscopy.com, the knee is the most commonly injured joint in the body. How can this be, if it performs such a simple function?
Each knee supports our total body weight every time we take a step. Walking after all, is a series of controlled falls. If the surface is flat and smooth, this is fairly simple. If the surface is uneven or textured, the hip, knee and ankle coordinate to balance and transfer weight allowing for the postural challenges with each step: the more uneven the surface, the more challenging.
Each time the foot hits the ground the body does immediate unconscious calculations, pooling information from the eyes, the feel of the ground and previous experience, to determine the best place to step, how large the step should be, where to place the foot, when to transfer weight and how much muscle strength to exert.
Wrong judgments at this point can result in trips, slips, falls, and resulting potential injury.
So the knee has to have more than a simple hinge action. In fact, detailed studies of gait have identified several other motions. One of these is a rotational type movement. In fact, simple walking involves 3 rotations in the lower limb. The knee must be able to adjust to all of them, beginning with a medial rotation (slight inward motion), to a lateral rotation (outward) as the heel begins to rise and during the swing stage, another medial rotation.
The major bones involved are the FEMUR (from hip to knee), the TIBIA (larger bone from knee to ankle, and the FIBULA (the thinner bone from knee to ankle). To allow for smooth operation of a closed system (inside the joint capsule) and to decrease wear and tear to the two major bones, the bones are lined with an articulating cartilage. There is also a cushioning surface on the Tibia called the Meniscus. This acts as a shock absorber.
The Femur is connected to the Tibia by two ligaments that tie them crosswise deep inside the knee (Cruciate or cross ligaments). There are also ligaments on each side of knee that assist in stabilization. In the front of the knee is the protective Patellar bone. This is connected to both the Femur and the Tibia by ligaments.
Outside this construction, the quadriceps and hamstrings cross the knee.
So, what affects your gait and how can ergonomics assist you?
Ergonomics dealing with the knee like all ergonomics, includes the basic concerns regarding biomechanics and posture - the relationship of your body to the world it's functioning in.
If you are not injured and have no physical problems, the main issues that ergonomics might focus on kneeling and squatting or lifting and carrying.
Lifting and squatting are major topics, so in this article the focus is walking.
Remember, walking is a complex act. If you carry things that affect your posture (unevenly weighted, carried on one side) or are awkward, it becomes even harder. Using stairs while carrying something that is large enough to block your vision or heavy enough the affect your balance or that doesnít have a good place to grip can create safety issues. If an elevator is available, thatís a better choice.
I have found that stair rails are very handy as assists for balancing large loads. This does depend on the design and height of the stair-rail and on the load, so use these techniques with caution. You can balance the load on the railing for a short rest, or while you readjust the load. You can also rest the load on the railing and slide it upward. This is safer going up, because the load rests against you as you move. Going down, gravity will be glad to assist you, but you may not be so glad of the result.
Vision and balance are more often issues going down stairs. If you cannot see the stairs and are at all uneasy, use the heel of the lead foot to locate the front of the riser you are on. Then slide your foot down until it is safely on the next riser. Then repeat this until you reach the bottom.
Sore knees can be caused by many issues, from arthritis or cysts to torn ligaments or meniscus, to tendonitis or muscle strain or simple overuse. A good site to visit for more specific information is the Mayo Clinic Symptom Checker at http://www.mayoclinic.com/health/symptom-checker/DS00671/SYMPTOM=43E2A918-2A5D-9994-E7C9F2A8BD7DC6A8&TAB=Knee%2520pain
If you have sore knees and must use stairs, work from the knowledge that your knees are essentially weight bearing joints. If the pain is sharp, strong, accompanied by swelling or persistent, you should see your doctor for a diagnosis and at a minimum get some strengthening exercises. The stronger your muscles are, the easier stair walking generally becomes.
I injured my knee one time and went to physical therapy for several weeks. I was helped initially by a techniqe calle 'taping' This involves a careful application of special tape to aide the muscles in maintaining themselves in proper alignment while they were weakened. Then, exercises which I still do today.
If you must use stairs, start by lining your hips up with the stairs. Stand up straight. Then, place your foot straight on the stair and breathe in. Then, as you breathe out, use the muscles of your hip - not your knee Ė to raise yourself up to the next riser. Do not rush. If you need to rest partway up, do so.
In going down stairs, the major issue is control. Remember, walking is controlled falling and on stairs this is even more evident. Hold on to the railing. Do not rush. Control is your friend.
If you use a cane, be sure you get adequate training in stair walking using your cane to assist. There is a trick to it that will make your life easier and safer. Your Occupational or Physical therapist will be able to help you. If you try to just hold your cane, it will get in the way and your return to good bilateral balance will be slowed.
There is a specialty field in ergonomics involved in the effect of shoe wear and a study of how different clothing affects the way you move (Really!). These studies affect design of clothing particularly for Fire and Police Personnel, mineworkers, astronauts and other special use groups. Over time some of these designs ideas leak into the general knowledge of manufacturers.