If your knees could speak, what would they tell you?
Here are ten issues I think your knees would discuss with you.
Memo from your knees:
I am the largest and most complex joint in the human body. The knee has been likened to a biologic transmission. In a car, a transmission is designed to accept and transfer loads between the engine and the wheels. The knee accepts loads from the lever arm of the femur, the longest bone in the body, and transfers the load down to the lower leg and foot. Knees typically work well and can last an entire lifetime. However, they are prone to injury and can wear out over time (20% of knees develop arthritis during the course of a lifetime). Here is some advice from your knees on how to keep your “knee transmission” running strong.
1. “Keep me moving”
Blood does not flow to the bearing surface of the knee (the cartilage or the inner portions of the meniscus). Instead, the cartilage and meniscus is bathed in joint fluid that provides nutrients to it. This joint fluid is like transmission fluid and is pumped throughout the joint by moving the knee. Without motion, the cartilage and meniscus is starved of its nutrition as the joint fluid does not circulate. Therefore, keep your knee moving – take walks, bike rides, hikes, etc.
2. “Understand the loads you are putting on me.”
Different activities impart very different loads across the knee. You should know the following chart:
Cycling = 1.2 times body weight across the knee
Walking = 3-5 times body weight across the knee
Stair Climbing = 5-7 times body weight across the knee
Running = 15 times body weight across the knee
When you go running, the magnitude of load you are subjecting your knee to is 10-15x more than when you go cycling. When your knee hurts, go spinning or swimming and don’t pound your knees into the pavement on a jog.
3. “Lighten my load”
Now that you understand how loading affects a knee, it is critical that you do not put excessive loads on your knees. The best way to unload your knee is to stay slim. Body weight matters and every pound on you is magnified at the level of the knee. For every pound you weigh, your knee feels it as 3-5 pounds when you walk and as 15 pounds when you run!! Think about it – if you lose 10lbs, you reduce your knee’s load by about 50 pounds when you walk and by 150 pounds when you run. That has an enormous effect on how long your knee will last.
4. “Share my load”
The muscles around the knee are the motor that drives the knee transmission but also absorb energy and dampen the load that your knee has to transfer. In fact, during normal walking, the muscles around the knee actually absorb more energy than they generate! As such, keep the hamstrings, quadriceps, and lower leg muscles strong – they take load off of the knee and protect it.
5. “Listen to me”
Your knee can’t speak but it can tell you when something is wrong. Your knee will alert you by swelling, hurting, locking, and buckling. It does this to try to tell you something. Please do not “play through” these things and go see a doctor.
6. “Keep me flexible”
Your knee is most efficient when it has a full range of motion. Stretch often to keep your knee limber and fresh. When it loses motion, your knee will have difficulty regaining it and will often lose progressively more motion over time.
7. “Get me fixed”
If your knee does break down, it needs to be fixed. Because it is the most complex joint in the body, your knee often does not respond well to injury. It doesn’t perform well when its ligaments are destroyed and they often need to be replaced or to be protected as they heal. Your knee’s menisci are prone to injury and either trimming or repair is often needed. This maintenance can often preserve its function.
8. “Respect me as I age”
We can’t reverse the aging process. As your knee get older, its cartilage and menisci become stiffer and less pliable. It has less capacity to transmit high loads and am more susceptible to injury. As your knee get older, you need to make sure you take better care of it – keep it moving to keep it lubricated, stay slim and build muscle to unload it, and incorporate low impact activities into your lifestyle.
9. “Pills, Shots, and Physical Therapy when I break down”
20% of the US population develops knee arthritis. We don’t know why this happens but it is almost part of the human condition. While the arthritic process is not reversible, anti-inflammatory pills such as NSAIDs (ibuprofen, Naprosyn) can reduce inflammation and ease pain. Steroid shots are often effective at reducing pain and viscosupplementation (gel) shots (such as synvisc, orthovisc, etc) can help lubricate the joint (like adding new transmission fluid). Physical therapy often helps by improving muscle function to unload your knee. Weight loss is often the most effective way to help a damaged knee and can relieve 40% of knee pain.
10. “They can rebuild me”
Sometimes a knee breaks down, and pills, shots, and physical therapy are no longer effective at keeping the knee transmission functioning. Excellent operations to rebuild the transmission are now available such as partial and total knee replacement. Although these rebuilt knee transmissions have less capacity than factory “original” knees that you were born with, they can provide excellent pain relief and restoration of function. Newer techniques such as robotic knee resurfacing provide durable pain relief and rapid return to activity.