Knee Ligaments

By Andrew Heideman PT/ATC

Knee Tendons medical vector illustration scheme, anatomical diagram. Educational information.

What you (K)need to know about the Knee Ligaments!

How many times have you been watching your favorite sporting event and heard an athlete that sprained a knee ligament, or even worse, tore it? Or, maybe you yourself have experienced some knee pain and don’t really know what to do about it?

Head, shoulders, knees and toes, knees and toes:

We learn this song as children, but do we actually know the functions of these structures or what to do if they get injured? The knee is a hinge joint, which is particularly important for weight bearing activities, such as walking, running and going up/down stairs. The load is distributed over the kneecap and can be up to 5 times the body weight, particularly when going down stairs. To better understand about knee ligaments and injuries associated with the knee, one must understand the structures and anatomy of the knee.

Knee Anatomy:

The four common ligaments of the knee are the Lateral Collateral Ligament (LCL), the Posterior Cruciate Ligament (PCL), and the two that are the most common to the public the Medial Collateral Ligament (MCL), and the Anterior Cruciate Ligament (ACL). The Patellar Ligament is also commonly referred to as the patellar tendon, but it is the ligament that connects the bottom of the knee cap (patella) and the top of the shin (tibia). Right above the patella is the quad tendon (quadriceps tendon) that connects the patella to the quads (muscles of the thigh). The meniscus is split into the medial and lateral aspects of the knee. These are cartilaginous “pillows” that rest on top of the tibia. The meniscus provides a cushion for the thigh bone (femur) to rest on the lower leg or shin.

The Collateral Knee Ligaments:

  • The LCL and the MCL are on each side of the knee to help with the side to side stability of the knee.
  • The MCL attaches the femur to the tibia while the LCL attaches the femur to the fibula (the smaller, non-weight bearing bone on the outside of the lower leg).

The Cruciate Knee Ligaments:

  • The ACL and the PCL are fibrous structures that make an X in the center of the knee. Both are connected on the femur and the tibia.
  • The PCL helps prevent the tibia from sliding backward when walking, running, etc. It goes from the back of the tibia to the front of the femur.
  • The ACL helps prevent the tibia from sliding forward apart from the rest of the leg. It goes from the front of the tibia to the back of the femur.

Injuries to the Knee Ligaments:

The ACL tends to be the most common injured ligament in the knee. The PCL has a better blood flow and healing tends to be better.

  • Sprains are categorized into three levels:
    1. Grade I Sprain – This is where the ligament stretches but does not tear.
    2. Grade II Sprain – When the ligament tears a little bit but does not completely tear.
    3. Grade III Sprain – This is a complete rupture of the ligament.

How to Diagnosis Knee Ligament Injuries:

If you think you have a knee ligament injury, ask yourself did you hear a pop when you got hurt? Is there swelling or maybe some discoloration of your knee? Does you knee feel unstable or loose? Any or all of these are signs of knee ligament injuries. If you suspect that you have a knee ligament injury then you should consult a medical professional. They will be able to perform a physical exam and point you in the right direction if they think you need further testing. Usually an X-ray will be the first test ordered to rule out fractures (broken bones). The next test would be a MRI. This will look at soft tissue injuries such as ligament tears or meniscal injuries. After the medical professional has given you a diagnosis they will give you a prognosis (plan of treatment). Some injuries are worse than others and require surgery.

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