Bursitis is the general term used to describe inflammation of any bursae. The bursae are the cavitary structures lined with synovial tissue that cushion and assist during the motion of joints and muscles. Bursitis is usually accompanied with tenderness; however, swelling and redness may also be present.
Pes anserine bursitis is a clinical entity that is associated with pain at the medial knee and upper tibial region. The term “pes anserine” comes from the Latin referring to “goose’s foot,” which the tendinous structures of the semitendinosus, gracilis, and sartorius muscles are said to resemble as they join to insert at the medial knee. The pes anserine bursa is sandwiched between the proximal medial tibia and the insertion point of the 3 tendons.
A more generic term, pes anserine pain syndrome, has been applied to refer to medial knee pain which may or may not include inflammation of the bursa sac. This article focuses on the clinical entity of pes anserine bursitis, unless otherwise specifically stated.
As in other knee conditions, mechanical derangement, direct trauma, obesity, and overuse have all been implicated in the development of pes anserine bursitis. Medial knee osteoarthritis is an early and common finding in patients with this condition. Sports that, in particular, may make one prone to pes anserine inflammatory conditions include running, basketball, and racquet sports.
The exact frequency of this condition in the general population is unclear as there is extensive overlap with other knee conditions. However, in one large study of over 10,000 persons, pes anserine pain was prevalent in approximately one-third of 1% of these individuals. The association of pes anserine pain (but not necessarily bursitis) with concomitant osteoarthritis was noted in one study to be over 90%.
Multiple reports suggest that pes anserine bursitis is more common in overweight middle-age females. There is an established association of pes anserine pain with diabetes mellitus. In many patients with established knee osteoarthritis, the inflammation of the pes anserine bursae may not be the primary pathology but rather a sequela of earlier knee complications.
Mechanical derangement at the medial knee joint is surmised to cause localized inflammation to the surrounding tendinous structures. This may include medial meniscus protrusion and displacement of the medial collateral ligament. Subsequently, the anserine bursa may become inflamed as well.
Patients with pes anserine bursitis likely will complain of pain on the inside (medial aspect) of the knee, in particular with rising from a seated position, going upstairs, or sitting with their legs crossed. The semitendinosus, gracilis, and sartorius function in unison in the act of crossing one leg over the other; thus, this motion typically will elicit the pain seen in pes anserine bursitis.
Additionally, there may be subjective complaints of muscle weakness and decreased range of motion of the knee joint.
Tenderness is invariably present over at the insertion of the pes anserine tendons, “goose’s foot,” at the medial knee and upper medial tibia. Swelling may or may not be present.
In patients with osteoarthritis, the clinician should have heightened suspicion for the possibility of pes anserine pain.
On physical examination, the affected knee should initially be evaluated in full extension. Tenderness will likely be present in the medial knee joint and may extend along the proximal, medial tibial region. With knee flexion to 90 degrees, tenderness may be palpated along the medial tendinous structures of the pes anserine group as they travel to insert along the medial tibial region. The pes anserine bursa lies directly beneath the tendons at their insertion.
Generally speaking, imaging does not assist with the diagnosis of pes anserine bursitis. However, plain knee radiographs are usually obtained to observe for any underlying bony abnormalities including osteoarthritis.
Ultrasonography may be used as an adjunct to evaluate for other causes of localized swelling, including joint effusions.
Though rarely indicated in an urgent setting, magnetic resonance imaging (MRI) may be useful in the assessing for knee pathology and ruling out alternative diagnoses.
Basics of initial therapy for pes anserine bursitis include the usual typical recommendations for many musculoskeletal disorders, including rest, ice, and short-term nonsteroidal anti-inflammatory drug use (unless otherwise contraindicated based on the patient’s medical history). Additionally, in the setting of obesity and deconditioning, weight loss and muscle strengthening exercises (in particular of the quadriceps muscle group) can be helpful for more long-term resolution of symptoms.
In patients with underlying osteoarthritis, treatment may need to be directed at this entity as well. Steroid injections are reserved for refractory symptoms but may be used initially with severe pain or in patients with nocturnal pain symptoms.
Additional modalities for treatment include therapeutic ultrasound, physical therapy, and transcutaneous electrical nerve stimulation (TENS).
The differential for a patient presenting with localized pain in the area of the pes anserine bursa is broad. It is paramount the treating clinician rules out of any infectious pathology such as septic bursitis or osteomyelitis. Gouty changes to the bursa are another diagnostic possibility. Neuropathic pain from compression of local structures (e.g., the saphenous nerve) may present similarly with medial knee discomfort. Furthermore, several other bursae may become inflamed (e.g., semimembranosus bursa or tibial collateral ligament bursa) within the knee joint, and the patient may present similarly.
Mass or space-occupying lesions within the knee that may present with medial knee pain include, but are not limited to, lipoma, hemangioma, giant cell tumor, tuberculosis, liposarcoma, and myelolipoma.
In the setting of trauma, medial meniscal tear or rupture must remain in the differential. Tibial stress fractures can occur in the setting of repetitive sports activities. Osteonecrosis can occur in those patients who are on long-term steroid therapy.
Less urgent pathology to include in the differential for pes anserine bursitis includes fat pad tenderness in overweight patients or fibromyalgia. In fibromyalgia patients, the pain is typically more symmetric and bilateral.
The prognosis of most cases of pes anserine bursitis is long-term resolution after limiting the inciting factors, including avoiding sports or repetitive activities that may worsen the patient’s pain. Duration of symptoms varies based on underlying conditions including osteoarthritis, obesity, and deconditioning.
Pes anserine bursitis refers specifically to the inflammatory condition of the bursal sac located between the muscular tendons (sartorius, gracilis, and semitendinosus) and their insertion at the proximal medial tibia.
These 3 muscles act to help in the “cross-legged” position. Thus, any repetitive activity that requires this form of motion may exacerbate the symptoms of the condition.
Underlying osteoarthritis, obesity, and the female gender are risk factors for developing this syndrome.
Treatment of pes anserine bursitis is generally supportive with steroid injections reserved for refractory cases.
Patients with pes anserine bursitis may be seen in all practice settings from outpatient offices, urgent care centers, and emergency departments. Referral to a specialist is not often needed unless the patient has another underlying condition that may be causing this syndrome or if there is unrelenting discomfort despite supportive measures.
Most data on diagnosis and treatment of pes anserine is derived from case series, relying heavily on expert opinions for direction and goals of care. (Level V)
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