The knee joint is the most common joint in the body to see conditions such as arthritis, tears, general pain and instability to develop. This has a lot to do with the design of the knee and the amount of wear and tear we place on it over the course of our lives. The knee is a somewhat unstable joint by design. It is a rounded bone, your femur, that sits on top of a flat bone, your tibia. This makes it an unstable joint and one that allows for a lot of slippage and movement of the bones on one another. Compound that with the fact that when we stand and place weight on our lower body, we are creating a closure of the joint itself under our body weight. These two factors are what leads to increased levels of pressure and friction in everyone’s knee joints.
However, there are five factors that are designed to prevent this friction and prolong the life of our knees IF these factors are functioning properly:
- Around every joint in your body you have a capsule: The job of this capsule is to act like plastic wrap and hold everything in place and reduce excessive amounts of movement in the joint. In most people, this capsule, this plastic wrap, is too tight and creates excessive pressure and closure on the knee joint. This creates more wear and tear and friction on the cartilage and the signs and symptoms of problems like arthritis get started.
- Due to its bony design, the knee has multiple ligaments to hold the bones in place and prevent to much excessive movement. In most people, while these ligaments are intact, but they do not stop excessive rotation of the lower leg. This extra rotation of the tibia allows for increased friction and thus the development of issues.
- The knee joint has some of the largest muscles around it to control its movement. These being your quadriceps and hamstrings. While these muscles do provide support to the knee joint, unfortunately, they are only well-equipped to control forward and backwards slippage of the joint, not side to side. Most knee problems develops because we don’t have good control of side to side slippage in the knee joint. The control to prevent side to side movement comes from muscles in your hips such as your gluteals, abductors and piriformis. By design these have to pull along a long tendon either to the inside or the outside of the knee to prevent this side to side slippage. While most people, even the most elite athletes, have fairly good strength in their quads and hamstrings, they do not have the necessary strength in their hips and glutes. This is the biggest problem that leads to knee pain and problems.
- These same large knee muscles (quads, hamstrings, and calf) tend to get very tight with any activity. Because they are such large, long and controlling muscles around the knee, any tightness or shortening in them causes a significant increase in joint closure and thus, increases in friction and pressure in the joint.
- Finally, your knee cap is a very mobile bone. It is designed to provide support to the knee and prevent some additional side to side slippage and rotation. However, it does not do a great job of this in most people. Your knee cap is designed to only move up and down in the groove in the femur when you bend and straighten your knee. Whether you realize it or not, frequently your knee cap is moving side to side at the same time it is moving up and down. This side to side shifting of the knee cap is allowing for side to side movement of the tibia on the femur and thus, increasing friction in the knee joint.
By Mike Bills, MS PT
