Protect Your Body: Knee Anatomy

When a first responder runs, the force of impact on the knee can be dramatic, and the entire knee anatomy, including the kinetic chain that connects the knee to surrounding muscles and bones, plays a huge role in knee health.

But it’s not just running that can be a risk factor: lunging, bending at the knee, and even stepping off stairs and curbs are potential movements that can lead to an injury.

Here are the main components of the knee that we believe everyone who has an active job should know.

Knee anatomy: Meniscus 

These “cushions” are between the femur (upper bone) and tibia (lower bone).  There is the lateral meniscus (outside of the knee) and medial meniscus (inside of the knee).  These structures undergo a lot of stress when the knee bends. Meniscus strain increases from 50 degrees of knee flexion to 90 degrees.  Considering this is a position our knees are in a lot, it would make sense that meniscal injuries are common among public safety workers.

If you have a meniscus injury some things that may bother you or cause you pain:

  • Running
  • Bending to pick up an object
  • Pain when rising after sitting for long period of time
  • Going up or down stairs

Usually, with a meniscus injury, pain will be in the lateral or medial (outside or inside) joint line or back inside part of your knee. You can usually touch and feel the area of pain. In extreme cases, you may feel deep clicking in or locking of the joint. This is typically associated with a meniscus tear called a “bucket handle tear” and usually requires surgical intervention.

Knee anatomy: ACL (anterior cruciate ligament)

The ACL is the knee injury that people are most familiar with. The ACL is a ligament inside of the knee that prevents the tibia (bottom bone) from sliding forward on the femur (top bone). In the first 10 to 30 degrees of knee flexion, there is a great degree of stress on the knee. That becomes even greater when there is a component of rotation. Typically, you will hear a pop in the knee when the injury occurs, as well as experiencing some pain and swelling.  Pain will be deep within the joint and not necessarily one that you can touch.

If you have an ACL injury you may experience pain or a sense of “instability” with the following:

  • Instability in moving side-to-side
  • Bending at the knee to pick something up
  • Pain stepping off a curb or step down from truck


Knee anatomy: MCL (medial collateral ligament)

MCL is a ligament that prevents gaping of the knee joint on the inside, and tears of this tissue are common. A lot of movement that first responders do – running, bending at the knee – put this ligament under stress. With this type of injury, you may or may not hear a pop in the knee when the incident occurs, but pain and swelling will be to the inside of the knee. There may also be some bruising, and the area will be very sensitive to the touch.

If you have an MCL injury you may experience pain with the following:

  • Moving side the side
  • Bending your knee
  • Rising after sitting for long period of time 
  • Moving after having leg straight for long period of time


Knee anatomy: Fibular head

The fibular head (on the outside of the knee) is held in place by the posterior ligament and fibular (aka lateral) collateral ligament. There is also a bursa just behind the fibular head. A common movement that puts this ligament at risk is when a foot gets trapped, but the knee moves. This will usually result in sharp pain on the outside of the knee. If this ligament is torn, the fibular head of the knee will have more instability and could cause the bursa to swell.  This can often be missed or misdiagnosed as a LCL tear or IT Band friction syndrome.

If you have a ligamentous injury to the fibular head, some things that may bother you or cause you pain:

  • Bending the knee while leaning over it, as if almost in a squat
  • Side to side movement

As experts in physical and athletic training, as well as having researched movement for decades, we know that changes to your exercise routine can and will help you prevent injuries to the components of the knee we’ve outlined above.

Want a visual perspective on this important joint? Click here for a video that offers great additional information.

Tune in next week for our favorite exercises to combat knee injuries, and if you have any questions about the material we’ve shared, please comment below and we’ll answer as soon as we can.

Dr. Trent Nessler

Dr. Trent Nessler

President of Rebound Vitality - Innovative wellness for first responders

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