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Pes Anserinus bursitis

Pes anserine bursitis (or pes anserinus bursitis) is an inflammatory condition of the medial knee. Especially common in certain patient populations, it often coexists with other knee disorders

Pes anserinus is the anatomic term used to identify the insertion of the conjoined tendons into the anteromedial proximal tibia. From anterior to posterior, the pes anserinus is made up of the tendons of the sartorius, gracilis, and semitendinosus muscles. The tendon's name, which literally means "goose's foot," was inspired by the pes anserinus's webbed, footlike structure. The conjoined tendon lies superficial to the tibial insertion of the medial collateral ligament (MCL) of the knee

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).

The 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. The prevalence of anserine bursitis in women may result from the broader female pelvis and the greater angulation of women's legs at the knees, placing additional stresses on these structures

Pes anserine bursitis is most common in young individuals involved in sporting activities and in obese, middle-aged women. This condition also is common in patients aged 50-80 years who have osteoarthritis of the knees.

Symptoms

  • Tenderness over the inner knee can occur, 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 can occur in the area during aggravating activities in individuals with arthritis of the knee or in obese females.
  • A history of athletic activity is another typical finding.
    • 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; as a result, the condition occasionally is called breaststroker's knee, although this term usually refers to MCL strains. MCL pathology may coexist among athletes or other individuals.

Differential diagnosis

  • MCL sprain can be excluded by physical examination or, if necessary, by 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 the 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.5,6 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 the above-described development of pes anserine bursitis. Inflammatory arthritis, such as gout and chondrocalcinosis, as well as septic arthritis, also can be associated with medial knee pain.
  • Semimembranosus tendinitis can occur with running or cutting activities. This condition is characterized by swelling over the posteromedial aspect of the knee and by tenderness with resisted flexion or valgus strain. An insertional enthesopathy of the semimembranosus muscle also has been described.
  • Panniculitis in the medial knee may occur in obese individuals. As in bursitis, the pain can worsen at night.
  • Stress fractures of the proximal medial tibia may produce pain in the area of the pes anserine bursa.
  • Osteonecrosis (death of subchondral bone due to an unknown cause) of the femur may present with sudden, severe medial compartment knee pain that is constant (day and night). Bone scanning shows increased uptake in the femoral condyle.
  • Osgood-Schlatter disease is an osteochondrosis involving traction apophysitis over the tibial tubercle in adolescent males.
  • Sinding-Larsen-Johansson syndrome is a traction apophysitis at the patella's junction with the patellar tendon.

Investigations

  • As a rule, radiography of the knee is not indicated for bursitis. Arthritis may be observed in older adults. In rare cases, young, athletic patients have an exostosis in the metaphyseal area.
  • MRI is the preferred imaging technique to help the clinician confirm the diagnosis.12,13
    • With MRI, the pes anserine bursa is observed between the pes anserinus (ie, the gracilis, semitendinosus, and sartorius tendons) and the upper tibial metaphysis. Axial imaging is important to differentiate the bursa from other medial fluid collections.

Treatment

Physical Therapy

Physical therapy is beneficial and often is indicated for patients with pes anserine bursitis. Rest and nonsteroidal anti-inflammatory drugs (NSAIDs) are first-line treatment. Other appropriate means of and ideas for treating pes anserine bursitis include the following:

  • Ice in foam cups can be applied and rubbed directly on the patient's skin (ice massage) for up to 10 minutes at a time. Other forms of cryotherapy (eg, cold packs) also may be used.
  • Ultrasonography has been reported to be effective in reducing inflammation associated with pes anserine bursitis.
  • Electrical stimulation has been used in other forms of bursitis, although its use has not been documented specifically in pes anserine bursitis.
  • Rehabilitative exercise for athletes with significant medial knee stress follows general physiatric principles for knee disorders (stretching and strengthening of the adductor and quadriceps groups [especially the last 30 º of knee extension using the vastus medialis muscle] and stretching of the hamstrings). For cases caused by restricted flexibility of muscles/tendons, stretching may promote significant reduction of tension over the bursa.
  • Advise older patients and those with chronic pain to avoid muscle atrophy from disuse. Address obesity in cases in which it is a contributing factor.
  • A small cushion placed between the thighs before sleeping is useful in medial knee bursitis.
  • If resective surgery is performed, the knee remains in extension or slight flexion within an immobilizer for 1-2 weeks after surgery. Pursue active range of motion (AROM) until 3 weeks postsurgery, and then begin progressive resistive exercises (PREs)

Intrabursal injection with local anesthetics and/or corticosteroids is a second line of treatment. A study found no difference in short-term pain relief afforded by 3-5 mL of 1% lidocaine with or without methylprednisolone. Injection can be directed to the point of maximal tenderness. Take care to avoid injection within the tendons themselves. Occasionally, an area 0.5-1 cm higher than the tendons is injected in order to include the MCL bursa, which also may be a pain generator. Relief is usually immediate but may not be complete.

Repeated lidocaine injections or the use of corticosteroids may result in longer-lasting relief (from 1 to several months). Generally, use a 22-gauge or 23-gauge needle to inject 1-3 mL of 1% lidocaine and corticosteroid (20-40 mg of triamcinolone, 20-40 mg of methylprednisolone, or 6 mg of betamethasone). If infection—which is rarer here than in the bursae of the anterior knee—is suggested, use a larger, 19- or 20-gauge needle and a 20-30 mL syringe for aspiration. Patients who do not respond to initial injection rarely respond to repeated bursal injections. Injection of the knee joint itself may be beneficial in recalcitrant cases.