History
Pes anserine bursitis can result from acute trauma to the medial knee, athletic overuse, or chronic mechanical and degenerative processes. This condition should not be overlooked when the diagnosis of osteoarthritis of the knee is made, because the 2 are commonly associated. [21] Typical findings in patients with pes anserine bursitis may include the following:
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Pain and tenderness over the inner knee – This may occur with arising from a seated position, at night, or with ascending (or, possibly, descending) stairs, though not usually with walking on level surfaces; although patients sometimes point to an area directly over the pes anserine bursa, they may often point to a diffuse region over the medial aspect of the knee; many of these patients also have plical irritation or medial joint compartment pathology (eg, medial meniscal tears or medial compartment arthritis)
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Local swelling
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Chronic refractory pain in the area during aggravating activities in individuals with arthritis of the knee or in obese females
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A history of athletic activity - Generally, susceptible persons are those who are involved in any sport that requires side-to-side movement or cutting; the incidence of pes anserine bursitis is higher among runners and in individuals who play basketball, soccer, and racket sports, in part because of the popularity of these activities
Pes anserine bursitis also has been reported in swimmers; accordingly, the condition occasionally is called breaststroker’s knee, although this term usually refers to medial collateral ligament (MCL) strains. Coexisting MCL pathology may be present among athletes or other individuals with pes anserine bursitis.
Physical Examination
The hallmark physical finding in pes anserine bursitis is pain over the proximal medial tibia at the insertion of the conjoined tendons of the pes anserinus, approximately 5-7 cm below the anteromedial joint margin of the knee. At its worst, pes anserine bursal pain is only mild to moderate. Intense pain could suggest a proximal tibial stress fracture.
The pes anserine bursa can be palpated at a point slightly distal to the tibial tubercle and about 3-4 cm medial to it (about 2 fingerbreadths). However, the bursa may not be palpable unless effusion and thickening are present. Palpable crepitus consistent with bursitis occasionally is noted. Pain in this area indicates an underlying inflammation of the pes anserine bursa or a bursitis.
Palpation of this area of the knee is important in a patient who complains of medial knee pain because the examiner needs to determine whether the pain is from joint-line pathology or pes anserine bursal pathology (or both). The 2 may coexist, because pes anserine bursitis can accompany primary knee pathology. Some researchers report pain along the medial joint line, mimicking a meniscal tear. As many as 30% of asymptomatic people may report tenderness when the area of the pes anserine bursa is pressed, so it is important to palpate the contralateral normal knee to verify that the pain on the affected side is more or reproduces their symptoms.
Concurrently with the physical examination, the hamstring-popliteal angle should be assessed to determine the patient’s underlying amount of hamstring tightness. This assessment is made by having the patient’s hip flex to 90° and then passively extending the leg. The angle formed between a perpendicular line to the femoral shaft and the tibial shaft is the hamstring-popliteal angle.
With the sports-related variant or pes anserine bursitis, symptoms may be reproduced by means of resisted internal rotation and resisted flexion of the knee. With the chronic variant in older adults, flexion or extension of the knee usually does not elicit pain. Valgus stress may reproduce the symptoms in athletic individuals, making it hard to distinguish pes anserine bursitis from MCL injuries using this technique alone. Typically, painful tenderness in association with MCL injuries is superior and posterior to the pes anserine bursa.
Noticeable bursal swelling is less frequent among elderly patients with concurrent arthritis. Bursitis is found more frequently on the right side than on the left, and approximately one third of patients have bilateral involvement. If swelling can be traced more proximally along the pes anserine tendons, a formal tendinitis may be present, and a snapping of the pes anserine tendons can occur. Two case reports of large cystic swellings of the bursa that resolved with conservative management have been documented.
An exostosis of the tibia has been described in athletes and may contribute to chronic symptoms.
A study by Colak et al indicated that in rare cases of pes anserine bursitis, intramedullary extension occurs, possibly mimicking a neoplasm clinically and radiologically. The investigators found that out of 542 patients with pes anserine bursitis, eight of them (1.48%) demonstrated bony changes. Radiographic appearance of these changes varied according to the depth of cortical scalloping and intramedullary extension. [22]
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Location of pes anserinus bursa on medial knee. MCL = medial collateral ligament.
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Pes anserinus bursa is located on proximomedial aspect of tibia between superficial medial (tibial) collateral ligament and hamstring tendons (ie, sartorius, gracilis, and semitendinosus). This bursa serves as space where motion occurs between these hamstring tendons and underlying superficial tibial collateral ligament.
