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What Happens When I "Tweak" My Knee

Understanding the Screw Home Mechanism of the Knee and how it affects your knee's longevity


The human body is a marvel of intricate design, and nowhere is this more evident than in the knee joint. One of the captivating features of the knee joint is the "screw home" mechanism. This mechanism plays a pivotal role in the smooth functioning of the knee during activities like walking, running, and even climbing stairs. In this blog post, we'll delve into the screw home mechanism of the knee, its significance, and the potential complications that arise when it doesn't work as intended.


The Screw Home Mechanism Explained

The screw home mechanism is a biomechanical phenomenon that occurs during the last stages of knee extension. As you straighten your knee from a bent position, the tibia (shin bone) undergoes a slight external rotation relative to the femur (thigh bone). This external rotation tightens the ligaments in the knee joint, allowing the joint surfaces to stabilize and lock in place. This is crucial for maintaining stability and conserving energy during activities that involve repetitive knee movements.


Significance of the Screw Home Mechanism

The screw home mechanism serves a twofold purpose. Firstly, it provides stability to the knee joint when it's fully extended. Imagine the importance of a stable knee joint when standing upright or engaging in weight-bearing activities. Secondly, this mechanism contributes to the efficient transfer of energy during walking and running. As the knee joint locks in extension, the leg functions as a rigid lever, minimizing energy expenditure and maximizing locomotion efficiency.


Complications When the Screw Home Mechanism Fails

When the screw home mechanism doesn't function properly, it can lead to a range of complications and discomforts:

  1. Instability: A malfunctioning screw home mechanism can compromise the stability of the knee joint, making it more susceptible to injuries and misalignments. This instability can result in a higher risk of falls and accidents.

  2. Pain and Discomfort: A faulty screw home mechanism can cause pain and discomfort in the knee joint. This pain may be exacerbated during activities that involve knee movement, such as walking, running, or climbing stairs.

  3. Gait Abnormalities: The screw home mechanism is closely tied to normal gait patterns. When it fails, it can lead to abnormal gait patterns, causing uneven wear and tear on joint surfaces and potentially leading to long-term joint problems.

  4. Reduced Efficiency: As mentioned earlier, the screw home mechanism aids in energy conservation during movement. Without it, the efficiency of movements like walking and running can be compromised, leading to quicker fatigue and reduced performance.

  5. Degenerative Changes: If the screw home mechanism consistently fails, it can contribute to degenerative changes within the knee joint. These changes might accelerate the development of conditions like osteoarthritis, which can be painful and debilitating.

In conclusion, the screw home mechanism of the knee is a remarkable example of the body's intricate mechanics.


If you feel like you "tweaked" your knee at some point and it hasn't fully recovered, you may have disrupted your knees screw home mechanism. We can identify this through exam and x-ray. Schedule a no charge consultation today!


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