Pes anserine is where the tendons of three muscles of the thigh insert in the anterior inner or medial side of the tibia below the knee joint. They are located superficial to the medial collateral ligament (MCL). These muscles are called from the medial/inner aspect of the leg to the lateral/outside aspect, Semitendinous, Gracilis, and Sartorius, respectively. Their function is to help with knee rotation stability, bending, and bringing knees together. Under the insertion, there is a bursa or a fluid-filled sac in which helps with decreasing the friction between the tendons and the bone. These bursas are also located in the heel, ankle, hip, elbow and shoulder.
Pes anserine bursitis is when there is an inflammation of the bursa that causes an increased amount of fluid which puts pressure on the knee. The most common cause of this inflammation is increased friction and stress on the knee seen with athletes or runners, direct hit, repeated pivoting and osteoarthritis. Other factors can contribute to this inflammation like: obesity, neglecting stretching before exercise, and medial meniscus or medial collateral ligament tears. The symptoms are increased pain bending or straightening the knee and tenderness below the joint line at the inside or medial of the knee.
The diagnosis can be made with the history, symptoms of the patient and the physical exam. The physician will palpate or touch the area where the insertion of the tendons are for any tenderness. These symptoms can present as a stress fracture so it is best to do an x-ray to make sure there is not one.
There are several treatments for Pes anserine bursitis. The patient can start with rest to decrease the friction of the bursa, doing stretching exercises or physical therapy, apply ice two or three times a day for 15-20 minutes, and take anti-inflammatory medicine like Naproxen or Ibuprofen. If the symptoms persist, drainage and a corticosteroid injection to the bursa can be done. If there is severity, the bursa can be removed with surgery. This surgery usually takes 2-3 weeks to heal.
