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11.21.06 (1 year ago)
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Background: Pes anserine bursitis is an inflammatory condition of the medial knee, especially common in certain patient populations, often coexisting with other knee disorders.
Pathophysiology: Pes anserinus is the anatomic term used to identify the insertion of the conjoined tendons into the anteromedial proximal tibia. From anterior to posterior, pes anserinus is made up of the tendons of the sartorius, gracilis, and semitendinosus muscles. The term literally means "goose's foot," describing the webbed footlike structure. The conjoined tendon lies superficial to the tibial insertion of the medial collateral ligament (MCL) of the knee.
Moshcowitz initially described pes anserine bursitis in the 1930s as an inflammation of the pes anserine bursa underlying the conjoined tendons of the gracilis and semitendinosus muscles and separating them from the head of the tibia. He defined the condition based on his observation of this type of bursitis in older adults with arthritis. He also described the musculi sartorii bursa between the tendon of the sartorius muscle and the conjoined tendons of the gracilis and semitendinosus, which can communicate with the pes anserine bursa proper. For the most part, both bursae are regarded collectively as the pes anserine bursa. In nonsurgical knees, there is usually no communication between these structures and the knee joint itself.
The sartorius, gracilis, and semitendinosus muscles are primary flexors of the knee. These 3 muscles also influence internal rotation of the tibia and protect the knee against rotary and valgus stress. Theoretically, bursitis results from stress to this area (eg, stress may result when an obese individual with anatomic deformity from arthritis ascends or descends stairs). Pathological studies do not indicate whether symptoms are attributable predominantly to true bursitis, tendonitis, or fasciitis at this site. Furthermore, panniculitis at this location has been described in obese individuals.
The muscles of the pes anserinus (ie, sartorius, gracilis, semitendinosus) are each supplied by different lower extremity nerves (ie, femoral, obturator, tibial, respectively).
Frequency:
In the US: One clinic reported finding pes anserine bursitis in 41 of 68 patients who were referred for presumed osteoarthritis of the knee. Bursitis in all locations of the body has been reported to account for 0.4% of visits to primary care clinics; however, incidence of bursitis in runners may be as high as 10%, including self-treated cases. In one review of 509 MRIs of symptomatic adult knees suspected of having an internal derangement, evidence of pes anserine bursitis was evident in 2.5%.
Mortality/Morbidity: In a descriptive study of 94 diabetic patients, pes anserine bursitis was reported in 91% of diabetic women and 9% of diabetic men. Among affected women with diabetes, 62% had the disease bilaterally. No subjects in a control group had bursitis without diabetes. Pes anserine bursitis is associated with obesity, and the diabetic patients in the study had greater body mass than the controls on average. Researchers, however, reported that body mass alone did not explain the higher incidence of bursitis among individuals with diabetes.
Race: No racial predilection is reported in the literature.
Sex: Incidence of pes anserine bursitis is higher among obese middle-aged women. Among older individuals with arthritis, a slight preponderance of females over males is noted among patients with pes anserine bursitis arthritis. This prevalence of women may be because of the broader female pelvis and greater angulation of the legs at the knees, placing additional stresses on these structures.
Age: Pes anserine bursitis is most common in young individuals involved in sporting activities and obese middle-aged women. This condition also is common in patients aged 50-80 years who have osteoarthritis of the knees.
History: Pes anserine bursitis can result from acute trauma to the medial knee, athletic overuse, or chronic mechanical and degenerative processes. An occurrence of pes anserine bursitis commonly is characterized by pain, tenderness, and local swelling. Typical findings reported within the subjective examination may include the following:
Tenderness over the inner knee with pain upon ascending and, possibly, descending stairs
Pain may be noted when arising from a seated position or at night. Patients typically deny pain with walking on level surfaces.
Local swelling may be noted.
Chronic refractory pain in the area during aggravating activities in individuals with arthritis of the knee or in obese females.
History of athletic activity
Generally, susceptible persons are involved in any sport that requires side-to-side movement or cutting. Incidence is higher among runners and individuals who play basketball, soccer, and racket sports, in part because of their popularity.
Pes anserine bursitis also has been reported in swimmers, which occasionally is called breast-stroker's knee, although this term usually refers to MCL strains. MCL Pathology
may coexist among athletes or other individuals.
Physical:
The hallmark physical finding is pain over the proximal medial tibia at the insertion of the conjoined tendons of the pes anserinus, approximately 2-5 cm below the anteromedial joint margin of the knee.
The bursa usually is not palpable unless effusion and thickening are present.
Palpable crepitus consistent with bursitis occasionally is observed.
With the chronic variant in older adults, usually no pain is experienced with flexion or extension of the knee.
Local pain is frequently noted in the area of the bursa, but, upon palpation, no pain should be noted at the joint line itself unless other conditions are active. Some researchers report pain along the medial joint line, mimicking a meniscal tear.
Noticeable bursal swelling is less frequent among elderly patients with concurrent arthritis. Bursitis is found more frequently on the right side than the left, and approximately one third of patients have bilateral involvement.
In the sports-related variant, symptoms may be reproduced with resisted internal rotation and resisted flexion of the knee.
Valgus stress may reproduce the symptoms in athletic individuals, making it hard to distinguish from MCL injuries. Typically, painful tenderness in association with MCL injuries is superior and posterior to the pes anserine bursa.
If swelling can be traced more proximally along the pes anserinus tendons, a formal tendonitis may be present, and a snapping of the pes anserinus tendons can occur.
An exostosis of the tibia has been described in athletes and may contribute to chronic symptoms.
Two case reports of large cystic swellings of the bursa that resolved with conservative management have been documented.
Causes:
Degenerative joint disease of the knee frequently is associated with bursitis. Up to 75% of patients with degenerative joint disease may have symptoms of pes anserine bursitis, according to some investigators.
Obesity is associated with pes anserine bursitis, particularly in middle-aged women.
Pes planus (ie, flat foot) may predispose patients to this bursitis and other problems in the medial knee.
Sporting activities that require side-to-side movement or cutting have been associated with pes anserine bursitis.
Local trauma, exostosis, and tendon tightness may predispose the patient to inflammation.
Diabetes has been linked with bursitis in one study; however, the extent to which the patient was able to control the diabetes was not documented
Differential diagnosis
Fibromyalgia
Hamstring Strain
Medial Collateral and Lateral Collateral Ligament Injury
Myofascial Pain
Osteoarthritis
Patellofemoral Syndrome
Prepatellar Bursitis
Stress Fracture
Other Problems to be Considered:
MCL sprain can be excluded by physical examination or, if needed, by magnetic resonance imaging (MRI).
Medial meniscus injury presents with medial joint line tenderness, knee locking, and/or catching. The McMurray test is positive with valgus stress and external tibial rotation. In older patients, a degenerative medial meniscus may present with insidious onset of medial knee pain.
Discoid medial meniscus synovial plica syndrome (medial plica) can result in point tenderness and palpable clicking over the medial femoral condyle.
Parameniscal cysts and dissecting synovial cyst (from another location) can cause swelling in the area.
Medial ligament syndrome is a poorly defined syndrome described in rheumatology literature as causing pain at the site of insertion of the MCL. Valgus stress exacerbates pain, and the patient may have pain behaviors. The etiology is unknown, but, in some cases, an inflammatory arthropathy, such as ankylosing spondylitis, is present. Medial ligament syndrome is treated with rest, heat, and a small corticosteroid injection.
Tumors in the region can include villonodular synovitis, osteochondromatosis, and synovial sarcoma. Synovial hemangioma, meniscal cyst, xanthomas, and ganglion cyst also may occur here.
Degenerative and chronic arthritis frequently involve medial knee structures and are associated with development of pes anserine bursitis, as described above. Inflammatory arthritis, such as gout and chondrocalcinosis, as well as septic arthritis, also can be associated with medial knee pain.
Of the more than 150 bursae in the body, at least 12 bursae are found in each knee, including the suprapatellar, prepatellar, infrapatellar, adventitious cutaneous bursa, gastrocnemius, semimembranosus, sartorius and anserine bursae, the No-Name-No-Fame bursa, and 3 lateral knee bursae located adjacent to the fibular collateral ligament and popliteus tendon laterally.
The prepatellar bursa overlies the anterior portion of the patella and can become involved with kneeling and leaning forward (housemaid's knee).
The superficial infrapatellar bursa lies between the skin and infrapatellar tendon; bursitis here is caused by kneeling or by a direct blow.
Deep infrapatellar bursitis presents with fluctuance and swelling that obliterate the depression on each side of the patellar tendon overlying the tibial tuberosity. Loss of full flexion and extension generally is observed.
The adventitious cutaneous bursa may be palpable as a swelling over the tibial tuberosity (adventitial bursae are those formed later in life through degeneration and do not have an endothelial lining).
Baker cysts arise from the gastrocnemius and/or semimembranosus bursa in the posterior knee. The gastrocnemius bursa lies between the medial head of the gastrocnemius and the joint capsule and communicates with the knee joint. The semimembranosus muscle sends tendon insertions to the posteromedial tibia behind the MCL, and a direct head inserts more posterior and distal as well. These insertions are superior and posterior to the insertion of the conjoined pes anserinus tendons and the pes anserine bursa.
The No-Name-No-Fame Bursa (referred to by Stuttle) also is called the MCL bursa and is located at the anterior border of the MCL. This bursa may be palpable during knee flexion as a small tender rounded nodule moving into the leading edge of the medial collateral ligament. Pain can be elicited on palpation of the bursa or by briskly extending the knee from a position of 90° flexion.
Pes anserinus tendonitis may exist exclusively or in conjunction with bursitis. So-called snapping tendonitis of the semitendinosus tendon is usually thought of as distinct from pes anserine bursitis, but some authorities classify it as the same inflammatory disorder.
Semimembranosus tendonitis also can occur with running or cutting activities. This tendonitis is characterized by swelling over the posteromedial aspect of the knee and tenderness with resisted flexion or valgus strain. An insertional enthesopathy of the semimembranosus muscle also has been described.
Panniculitis may occur in an obese individual in the medial knee. Pain can be worse at night, as in bursitis.
Stress fractures of the proximal medial tibia may produce pain in the area of the pes anserine bursa.
Osteonecrosis (death of subchondral bone of unknown cause) of the femur may present with sudden severe medial compartment knee pain that is constant (day and night). Bone scan shows increased uptake in the femoral condyle.
Osgood-Schlatter disease is an osteochondroses involving traction apophysitis over the tibial tubercle in adolescent males.
Sinding-Larsen-Johansson syndrome is a traction apophysitis at the junction of the patella with the patellar tendon.
Nerve injuries causing medial joint pain include trauma to the saphenous nerve or injury during knee surgery, especially arthroscopy. Pain can be reproduced with Tinel sign. One case report documents distal tibial pain from entrapment of the saphenous nerve caused by pes anserine bursitis. Medial knee pain associated with back pain also could represent an L3-L4 radiculopathy. Electrodiagnostic testing such as electromyography (EMG) and nerve conduction velocity tests may be useful.
Fibromyalgia has characteristic tender areas or trigger points, one of which includes the medial aspect of the knee.
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