(Fig 3-A.35) Semimembranosus Arms with Bursitis: Anterior, Direct, Inferior

https://youtu.be/fEW4WagXOs8

https://youtu.be/GSIg93UH3Oc

 

📌 Case study

✅Semimembranosus Bursitis Overview

• The semimembranosus bursa, a horseshoe-shaped synovial bursa, is located around the semimembranosus tendon near the posteromedial tibial rim. When inflamed, it forms a synovial-lined space that wraps the tendon, visible as a characteristic reverse 'J' shape on imaging.

✅Direct Arm Anatomy

• The Direct Arm of the semimembranosus tendon attaches directly to the posteromedial aspect of the tibia, just distal to the joint line.

✅Anterior Arm Details

• The anterior arm inserts into the medial proximal tibia, above the insertion of the superficial MCL, and passes beneath the posterior oblique ligament. It has an almost horizontal course and is visible on coronal images as a round, hypointense structure adjacent to the medial tibia, under the MCL.

🔹Posterior Oblique Ligament Connection

• The posterior oblique ligament attaches to the sheath of the semimembranosus tendon, blends with the posterior margin of the superficial MCL, and runs superficially to the anterior arm of the semimembranosus tendon.

✅ Inferior Arm Divisions

• The inferior arm of the semimembranosus tendon is split into medial and lateral divisions. 
• The medial division attaches to the medial tibia and extends anteriorly toward the posterior margin of the medial collateral ligament.
•  The lateral division passes over the popliteal fascia and the popliteus muscle, further emphasizing its structural significance.

 

Semin Musculoskelet Radiol. 2016 Feb;20(1):12-25

Arthroscopy. 2017 Feb;33(2):400-407

Skeletal Radiol. 2014 Jun;43(6):781-91. 

MRI Web Clinic - June 2018 Medial Supporting Structures of the Knee with Emphasis on the Medial Collateral Ligament

Radiographics. 2015 Jul-Aug;35(4):1123-37

 

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