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The Popliteus

Introduction/anatomy 

As you may have learned in previous blogs, the knee region is made up of several structures. These are both passive structures (ligaments, meniscus, bone) and active structures (muscles). Several large muscles provide the ability to move in the knee. We are probably all familiar with these as well. 

  • At the front, the quadriceps provide the stretching of the knee. 
  • At the back, the hamstrings take care of bending and rotating the knee. 

Located deeper at the back of the knee we find another muscle; the popliteus. This muscle runs from the back/outside of the knee inward (see image). On the outside, the muscle attaches to what we call the lateral epicondyle of the femur. This is the most protruding bone point on the outside of the knee. Also, in this region, the popliteus has fibers that "fuse" with the lateral knee ligament and lateral meniscus. It is a muscle that runs relatively horizontally and then diagonally. So not primarily straight down like the quadriceps do. The popliteus further attaches to the back on the medial (inner) side of the tibia. 

Function

Because of the course of this muscle, it has an important function in rotating the knee inward when it is extended. In addition, it is a muscle that is active in the bending of the knee and has an important supporting role for the posterior cruciate ligament. Together they ensure that the knee has sufficient stability to prevent the lower leg from sliding backwards in relation to the upper leg. Because the muscle has a function in the inward rotation of the knee, it also provides extra stability when the leg rotates outward. The popliteus also inhibits this movement. 

Injuries

Complaints to this muscle can arise in a variety of ways. This can be both acute (as in a trauma) and gradual. With complaints that develop gradually, the chance that there is injury (damage) is small. This is because injury generally requires large sudden forces whereby damage also occurs at that time. So you really remember a clear genesis moment to which a trauma (such as a fall) is connected.

Overload 

In the case of complaints that arise gradually, we are more likely to speak of an overuse complaint. Such an overload can occur for various reasons. The most common are; 

  • Reduced control due to dysfunction of muscles in the foot, knee or hip. 
  • Increasing training intensity (too quickly). 
  • Too little rest/recovery time between load moments. 
  • Changes in running such as surface, uneven load or footwear. 

An overuse complaint of the popliteus is something that we see occurring mainly in people who run a lot or walk in hilly areas (mainly downhill walking). This is because the muscle simply has to show more activity during such activities. Complaints that can occur with this symptom are; 

  • Feeling as if the knee area is thickened (swollen), this can also feel pinched. 
  • Pain symptoms when running or walking down hill. 
  • A limitation in mobility of the knee during extension or flexion.

Trauma

If symptoms have developed after trauma, injury may present itself. Injuries involving the popliteus often involve injury to other structures as well. For example, damage to the outer meniscus and/or lateral knee ligament often also occurs. Damage to the posterior cruciate ligament may also occur. Given the location where this muscle attaches and the functions it has, this is actually quite logical. Forces that are large enough to injure this muscle are also exerted on the other structures with which the muscle shares a function or has an attachment. Often, these are movements whereby too much rotational force is applied to the knee or movements whereby the lower leg is shifted backwards with very great force in relation to the upper leg. In this case, the symptoms are also reminiscent of injuries to meniscus or posterior cruciate ligament. This means that, for example, pain and swelling can be present, movement can be limited and a feeling of instability is not unusual. 

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The relationship between the lateral meniscus and popliteus is beginning to appear increasingly relevant. New insights imply that after trauma the fibers between the popliteus and lateral meniscus can be damaged. Something that untreated can lead to permanent instability of the lateral meniscus. 

This cause for instability symptoms has already been demonstrated in several patients with symptoms in which no abnormalities were actually visible on MRI. Also, in these cases, physical examination aimed at lateral or posterolateral instability did not provide clarity. The only exception was that the Figure-4 test was positive in all these patients. In this case, recognizable pain was present at the lateral side of the knee. These patients were examined by keyhole surgery and any instability was repaired. 

Physiotherapy at Fysio Fitaal

At Fysio Fitaal in Tilburg we are specialized in the treatment of various knee problems and the counseling of patients after surgery. Are you suffering from unexplained knee complaints or are you facing a rehabilitation? Contact us and together we will ensure a speedy recovery with a personalized plan!

 

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