Pes anserine bursitis is an inflammatory condition of the medial (inner) knee at the bursa of the pes anserinus

Pes anserinus

Pes anserinus is the anatomic term used to describe two different structures:* Pes anserinus * Pes anserinus...

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Pathology

The pes anserinus is the anatomic term used to identify the insertion of the conjoined tendons Sartorius

Sartorius muscle

The Sartorius muscle – the longest muscle in the human body – is a long thin muscle that runs down the length of the thigh. Its upper portion forms the lateral border of the femoral triangle.-Origin and insertion:...

, Gracilis

Gracilis muscle

The gracilis is the most superficial muscle on the medial side of the thigh. It is thin and flattened, broad above, narrow and tapering below.-Origin and insertion:...

, and Semitendinosus into the anteromedial proximal tibia

Tibia

The tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones....

. Theoretically, bursitis

Bursitis

Bursitis is the inflammation of one or more bursae of synovial fluid in the body. The bursae rest at the points where internal functionaries, such as muscles and tendons, slide across bone. Healthy bursae create a smooth, almost frictionless functional gliding surface making normal movement painless...

 results from stress to this area (eg, stress may result when an obese individual with anatomic deformity from arthritis ascends or descends stairs). An occurrence of pes anserine bursitis commonly is characterized by pain, especially when climbing stairs, tenderness, and local swelling.

Muscles involved

• Sartorius
  Sartorius muscle
  The Sartorius muscle – the longest muscle in the human body – is a long thin muscle that runs down the length of the thigh. Its upper portion forms the lateral border of the femoral triangle.-Origin and insertion:...
  
   aids in knee and hip flexion, as in sitting or climbing; abducts and laterally rotates thigh; innervated by the femoral nerve
  Femoral nerve
  The femoral nerve, the largest branch of the lumbar plexus, arises from the dorsal divisions of the ventral rami of the second, third, and fourth lumbar nerves...
  
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• Gracilis
  Gracilis muscle
  The gracilis is the most superficial muscle on the medial side of the thigh. It is thin and flattened, broad above, narrow and tapering below.-Origin and insertion:...
  
   flexes and medially rotates tibia at knee; innervated by the obturator nerve
  Obturator nerve
  The obturator nerve in human anatomy arises from the ventral divisions of the second, third, and fourth lumbar nerves; the branch from the third is the largest, while that from the second is often very small.-Path:...
  
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• Semitendinosus flexes knee; medially rotates tibia on femur when knee is flexed; medially rotates femur when hip is extended; counteracts forward bending at hips; innervated by tibial nerve
  Tibial nerve
  The tibial nerve is a branch of the sciatic nerve. The tibial nerve passes through the popliteal fossa to pass below the arch of soleus.In the popliteal fossa the nerve gives off branches to gastrocnemius, popliteus, soleus and plantaris muscles, an articular branch to the knee joint, and a...
  
   and common fibular nerve
  Common fibular nerve
  The common fibular nerve , about one-half the size of the tibial nerve, is derived from the dorsal branches of the fourth and fifth lumbar and the first and second sacral nerves.It descends obliquely along the lateral side of the popliteal fossa to the head of the fibula,...
  
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