Investigations of the Popliteus

 

Overview

 

Here is a good introduction to the functioning of the popliteus system from 2008:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2899169/

 

In recent years, the posterolateral corner of the knee has received much attention. This is because of the significant role it plays in providing posterolateral rotation and varus stability to the joint [2]. This is particularly so in the case of the popliteous muscle (PM). Several functions are attributed to it. Some of those functions are derived from its capacity to invert its origin and insertion point, depending on whether it is fixed on the femur or the tibia. In this way, its two main functions are considered to be the internal rotation of the tibia in the already extended knee and external rotation of the femur over the fixed tibia [5].

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

http://pubs.rsna.org/doi/pdf/10.1148/radiographics.20.suppl_1.g00oc02s91

 

The popliteus tendon sends attachments to the lateral meniscus (the popliteal meniscal ligament) and to the styloid process of the fibula (the popliteal fibular ligament)... The popliteus muscle is the main lateral stabilizer of the knee and also an internal rotator of the tibia... The popliteal meniscal ligament prevents the lateral meniscus from excessive forward displacement during extension of the knee... The popliteal fibular ligament acts as a pulley, fixing the muscle in position during contraction...

 

So what would happen if the pulley did not work and the popliteus muscle was not held in place during contraction...??? Or the PFL holds the popliteus muscle in place when the leg is straight / extended...???

 

 

http://www.acr.org/Education/Education-Center/Course-Materials/~/media/3FFC290B932E4F9E9767B58A279C7BDC.pdf

 

The majority of popliteus tears are extraarticular, involving the muscular or myotendinous portion, although they can be intraarticular at the level of the popliteal hiatus and at or near the femoral insertion. Such injuries can also be a mixture of intraarticular and extraarticular...

 

 

 

MRI investigations of the Popliteus

 

 

http://pubs.rsna.org/doi/pdf/10.1148/radiographics.20.suppl_1.g00oc02s91

 

The posterolateral structures may not always appear on images obtained with routine MR imaging protocols.Yu et al... propose use of a coronal oblique plane; with a coronal plane slanted parallel to the direction of the popliteus tendon..., they were able to achieve better visualization of the arcuate, fabellofibular, and popliteal fibular ligaments.

 

 

http://www.acr.org/Education/Education-Center/Course-Materials/~/media/3FFC290B9

32E4F9E9767B58A279C7BDC.pdf

 

... recommend that a specific MRI protocol, which includes the entire fibular head and styloid on all imaging sequences, be used to best identify these structures when a posterolateral knee injury is being evaluated on MRI.

 

 

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1724686/  (See PDF)

 

MRI is helpful in the evaluation of complex knee injuries. Some authors have suggested that the posterolateral structures of the knee may be better visualised by using a coronal oblique plane slanted parallel to the direction of the popliteus tendon,14 whereas others have recommended a standard knee protocol using high contrast images with fat suppression.3 5 Popliteus musculotendinous injuries are detected in 1% of all knee MRI examinations,5 commonly associated with damage to other posterolateral structures. Most of these popliteus ruptures are extra-articular, involving the muscular or musculotendinous portion but they can be intra-articular, at the level of the popliteal hiatus or at the femoral insertion.5 14 Fewer than 10% of popliteus injuries are isolated.5 14 They may appear on MRI as an avulsion of the tendon from its femoral attachment, an irregular contour of the tendon at the popliteal hiatus with surrounding high signal intensity changes due to oedema, or as swollen disorganised muscle fibres with high signal intensity changes within the popliteus muscle.5 14

 

It would appear that most popliteus musculotendinous injuries are extra-articular, and are often associated with damage to other posterolateral structures. Therefore all arthroscopic investigations would require a third insertion point to ensure a thorough examination.

 

 

Arthroscopic investigation of the Popliteus

 

I have had an arthroscopy procedure to repair a tear in the lateral meniscus of my right knee. I have been told that the surgeon would also have checked to see if there were any other problems whilst in there.

 

But with only 2 insertion points, how can they have checked thoroughly for a problem with the Popliteus tendon? Especially bearing in mind that this was what I had been asking about from the initial consultation onwards?

 

 

http://pubs.rsna.org/doi/pdf/10.1148/radiographics.20.suppl_1.g00oc02s91

 

The popliteus tendon arises below the lateral collateral ligament in a small sulcus on the lateral femoral condyle, passes under the lateral collateral ligamnet, descends into the popliteus hiatus, then passes under the arcuate ligament and becomes extraarticular before finally joining its muscle belly, which attaches to the posteromedial surfaceof the proximal tibia...

 

 

http://www.ncbi.nlm.nih.gov/pubmed/18237701

Arthroscopy. 2008 Feb;24(2):174-7. doi: 10.1016/j.arthro.2007.08.018. Epub 2007 Nov 5 found that:

Abstract

PURPOSE:This study was conducted to define what portion of the normal popliteus musculotendinous unit can be visualized during standard diagnostic arthroscopy.

Conclusions

On standard knee arthroscopy, less than half of the normal popliteus tendon is visible, and the femoral insertion and musculotendinous junction are not visualized. Because most reported popliteus injuries have occurred here, reliance on arthroscopic visualization alone is inadequate.

Clinical Relevance

The limitations of arthroscopic visualization of the normal popliteus tendon have implications for the diagnosis and treatment of posterolateral corner injuries.

 

 

It seems to me that the results of my arthroscopy cannot truly be relied upon to make a diagnosis about the popliteus complex after my jogging injury.

 

And, to me, this is further compounded by the fact that I have been, and still am, getting stabbing / throbbing pains around my knee. These stabbing pains appeared to be coming from the North, South, East and West as they entered my knee, but latterly they are predominantly at the lateral and medial sides, with the lateral being by far the worse.

 

I had had an ultrasound examination of my knee, and whilst investigating the lateral side, they also checked around the medial side. Although they recorded nothing abnormal, I had immense stabbing pains as the ultrasound scanner was moved over the medial side of my knee. This was a great surprise to me because I hadn't experienced pain here before this day. No explanation was given for this pain.

 

I wonder on whether these stabbing pains are caused by lose fragments of bone moving around my knee, extra-articularly...?

 

Or, on re-reading my post-arthroscopy paperwork, this may well be crepitus associated with chondromalacia...?