Pes anserine bursa !
The pes anserine bursa is a fluid sac on the upper inner shin bone, under three tendons; inflamed, it hurts below the inner knee.
Official name: Anserine bursa
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What it is
A fluid sac under the three tendons on the inner tibia.
What it does
Reduces friction; it can become painful (pes anserine bursitis).
Key facts
- Where
- Between pes anserinus tendons (sartorius, gracilis, semitendinosus) and MCL on medial tibia
- Function
- Reduces friction of these tendons over MCL and tibia; site of pes anserine bursitis
Relations
- Superficial
- Sartorius, gracilis and semitendinosus tendons, fanning out together onto the upper medial tibia (pes anserinus)
- Deep
- Tibial insertion of the superficial medial collateral ligament and the medial flare of the tibia
- Above
- Medial joint line and the medial meniscus
How to find it
With the knee slightly bent, the hamstring tendons are followed from the back of the knee forward onto the flat upper medial tibia; the bursa lies under them, below the joint line and medial to the level of the tibial tuberosity, where pes anserine bursitis causes point tenderness and sometimes soft swelling.
On imaging
Ultrasound may show a fluid collection between the pes tendons and the medial collateral ligament, but often shows no fluid, so the diagnosis is largely clinical. MRI separates it from a meniscal tear or cyst, an MCL injury and a stress fracture of the medial tibia.
Clinical notes
- Medial knee pain differential: medial meniscus tear and medial osteoarthritis (joint-line tenderness), MCL sprain (along the ligament), tibial stress fracture, pes anserine bursitis (below the joint line)
- At hamstring graft harvest the infrapatellar branch of the saphenous nerve, which crosses this area, can be injured, leaving numbness below the knee
- Many people with the typical tender spot show no fluid in the bursa on ultrasound or MRI, so the condition is often called pes anserine pain syndrome (tendinobursitis) and is diagnosed clinically
Memory aid
Pes anserinus tendons from front to back: "Say Grace before Tea" (Sartorius, Gracilis, semiTendinosus).
Test yourself
Think of the answer, then tap the question to see it.
Where is the tenderness of pes anserine bursitis, and why does it matter?
A few centimetres below the medial joint line on the upper medial tibia, not on the joint line, which tells it from a medial meniscus tear.
Between which structures does the pes anserine bursa lie?
Between the sartorius, gracilis and semitendinosus tendons and the superficial medial collateral ligament on the medial tibia.
With which knee condition does pes anserine bursitis often coexist?
Medial knee osteoarthritis; it is also linked to obesity, diabetes and running.
Educational information, not medical advice. For any symptom, see a health professional.
Its names
- Official Latin (TA2)
- bursa anserina; bursa subtendinea musculi sartorii TA2 2743
- Official Spanish (DeCS)
- Bolsa anserina DeCS D002061
- English (TA2)
- Anserine bursa
Related
Sources: Terminologia Anatomica (TA2); DeCS; Anatomy, Skin Bursa; Anatomy, Bony Pelvis and Lower Limb, Knee.
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Representative model, for educational purposes only.
