As you may have learned in previous blogs, the knee region consists of several structures. These are both passive structures (ligaments, meniscus, bone) and active structures (muscles). Several large muscles provide ability to move in the knee. We are probably all familiar with these as well.
- At the front, the quadriceps take care of stretching the knee.
- At the back, the hamstrings take care of bending and rotating the knee.
Deeper to 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. The popliteus also has fibers in this region 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 as the quadriceps do. The popliteus further attaches to the back on the medial side (inside) of the tibia (tibia).
Because of its course, this muscle has an important function in rotating the knee inward when it is extended. In addition, it is a muscle that is active in bending 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 shifting backward relative to the upper leg. Because the muscle has a function in turning the knee inward, it also provides extra stability when the leg turns outward. The popliteus also inhibits this movement.
Complaints to this muscle can occur in a variety of ways. This can be either acute (as in a trauma) or gradual. With complaints that develop gradually, there is little chance that there is injury (damage). This is because injury generally requires large sudden forces where damage occurs at that time. So you then really remember a clear moment of origin to which a trauma (such as a fall) is connected.
In complaints that arise gradually, we are more likely to speak of an overuse complaint. Such overuse can occur for a variety of reasons. The most common are;
- Reduced control due to dysfunction of muscles in the foot, knee or hip.
- (Too rapidly) increasing training intensity.
- Not enough rest/recovery time between load moments.
- Changes in running such as surface, uneven load or footwear.
An overuse complaint of the popliteus is something we see occur mainly in people who do a lot of running or walking in hilly areas (mainly when walking downhill). This is because the muscle simply needs to show more activity during such activities.
Complaints that may occur with this symptom are;
- Feeling as the knee hollow is thickened (swollen), this can also feel pinching.
- Pain symptoms when running or walking downhill.
- A limitation in mobility of the knee during extension or flexion.
If symptoms developed after trauma, injuries may present themselves. 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 can also occur. Given the location where this muscle attaches and the functions it has, this actually makes sense. Forces large enough to injure this muscle are also exerted on the other structures with which the muscle shares a function or has an attachment. These are often movements in which the rotational force on the knee is too great or movements in which the lower leg is moved backwards with great force. In this case, the symptoms will be similar to those of a meniscal or posterior cruciate ligament injury. This means that, for example, pain and swelling may be present, restriction in movement and also a feeling of instability is not strange.
The relationship between the lateral meniscus and popliteus is beginning to look increasingly relevant. New findings imply that after trauma, the fibers between the popliteus and lateral meniscus can be damaged. Something untreated can lead to permanent instability of the lateral meniscus.
This cause for instability complaints has already emerged in several patients in complaints where no abnormalities were actually visible on MRI. Also in these cases, physical examination aimed at lateral or posterolateral instability did not provide any clarity. The only exception was that the Figure-4 test was positive in all these patients. There were recognizable pain symptoms on the lateral side of the knee. These patients were examined by keyhole surgery in which any instability was repaired.
Physical therapy at Fysio Fitaal
At Fysio Fitaal in Tilburg, we specialize in the treatment of various knee problems and assisting patients after surgery. Have you been walking with unexplained knee problems or are you facing rehabilitation? Please contact us and together we will provide you with a personalized recovery plan!
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