Written by Sander van Bergen24-10-2013 12:14:14. Posted in Knee

Test your knowledge: the ‘popliteus musculotendinous unit’

Question:

This week we’ll discuss an important anatomic structure which is present in the popliteal fossa of all human knees: the ‘popliteus musculotendinous unit’ (PMTU). This is an important part of the posterolateral structures in the knee and basically runs from the proximal tibia to the distal lateral femur condyl. However, the PMTU has more complex, multiple extensive connective tissue attachments.  

- Do you know the attachment places of the popliteal muscle? 
- What is the main function of this muscle in relation to its attachment? (multiple answers possible!) 

See the answer of this question below the image!

Answer:

The popliteus muscle is attached to the posteromedial surface of the proximal tibia (triangular shaped) and forms the interior part of the floor of the popliteal fossa. The tendon runs between the fibrous capsule and the synovial membrane to the lateral surface of the lateral condyle, but dorsal and medial of the lateral collateral ligament (LCL) of the knee. When the knee is extended, the attachment of the tendon is located posterior to the lateral collateral ligament, in flexion the tendon moves under the LCL to anterior. The popliteus musculotendinous unit has multiple extensive attachments: among others to the arcuate ligament complex and the oblique popliteal ligament, other fascicles are fusing into the lateral meniscus. A strong attachment to the fibular head is commonly found and is described as the popliteofibular ligament.   

The popliteal muscle tendon unit (PMTU) is likely to have more than one function: 
-  A significant contributor to posterolateral stability of the knee joint; 
- Some studies describe the popliteus muscle as a retractor of the lateral meniscus. This is however subject to debate; 
- Many studies emphasize the role of the popliteus muscle as an internal rotator of the tibia (or lateral rotator of the femur); 
- The popliteus muscle has an ability to ‘open’ the locked knee joint; 
- The popliteus muscle is suggested to play an important role in restricting hyperextension of the knee joint; 
- Passive stretch of the popliteus muscle in hyperextension can lead to a myotatic reflex response which can facilitate stability in extension.