Snapping Pes Anserinus Syndrome

Snapping Pes Anserinus Syndrome – The Clinical Syndrome

Snapping pes anserinus syndrome, which is also known as snapping pes syndrome , is a constellation of symptoms that includes a snapping sensation in the knee associated with sudden, sharp pain in the area of the tibial condyle. The snapping sensation and pain are the result of the semitendinosus and gracilis tendons impinging on the tibial condyle. Bony excrescence of the tibial condyle as well as abnormalities of the pes anserinus and associated bursae have been implicated in the pathogenesis of snapping pes anserinus syndrome as has the extended wearing of high-heeled shoes, which can increase genu recurvatum. Overload trauma to the anterior knees from repetitive static vertical jumping when playing has also been reported to cause snapping pes anserinus.

The symptoms of snapping pes anserinus syndrome occur most commonly when the patient begins to extend his or her knee from a fully flexed position. As the knee passes just beyond neutral position, snapping and pain occurs. Often, pes anserine bursitis coexists with snapping pes anserinus syndrome, further increasing the patient’s pain and disability.

What are the Symptoms of Snapping Pes Anserinus Syndrome

Physical examination reveals that the patient can recreate the snapping and pain by extending his or her knee from a fully flexed position. Point tenderness over the pes anserine bursa indicating pes anserine also is often present. If the patient has a significant component of pes anserine bursitis, a positive resisted extension release test may be present. This test is performed by having the patient assume the sitting position with the affected knee fully flexed. The examiner firmly grasps the patient’s anterior ankle and has the patient extend the knee against the examiner’s resistance. The examiner suddenly releases the resistance against the patient’s active extension. This sudden release of resistance markedly increases the pain over the pes anserine bursa if the patient has pes anserine bursitis.

How is Snapping Pes Anserinus Syndrome diagnosed?

Plain radiographs are indicated in all patients with pain thought to be emanating from the knee to rule out occult bony pathological processes and tumor. Based on the patient’s clinical presentation, additional tests may be indicated, including complete blood count, prostate-specific antigen, erythrocyte sedimentation rate, and antinuclear antibody testing. Magnetic resonance imaging (MRI) and ultrasound imaging of the affected knee are indicated if occult mass or aseptic necrosis is suspected and to help confirm the diagnosis. The following injection technique serves as a diagnostic and therapeutic maneuver.

Differential Diagnosis

Snapping pes anserinus syndrome frequently coexists with pes anserine bursitis, arthritis, and internal derangement of the knee, which may require specific treatment to provide palliation of pain and return of function. Occasionally, snapping pes anserinus syndrome can be confused with iliotibial band syndrome because of the snapping phenomenon. Other causes of snapping knee including snapping plica syndrome, snapping meniscus syndrome, snapping popliteus tendon, and snapping to intra-articular bodies must also be considered. The clinician must consider the potential for primary or secondary tumors of the knee in the differential diagnosis of snapping pes anserinus syndrome.

Treatment

A short course of conservative therapy consisting of simple analgesics, nonsteroidal antiinflammatory drugs (NSAIDs), or cyclooxygenase-2 (COX-2) inhibitors is a reasonable first step in the treatment of patients with snapping pes anserinus syndrome. The patient should be instructed to avoid repetitive activity that may be responsible for the development of snapping pes anserinus syndrome, such as running on sand. If the patient does not experience rapid improvement, injection of local anesthetic and steroid in the area overlying the tibial condyle is a reasonable next step.

Complications and Pitfalls

Care must be taken to rule out other conditions that may mimic the pain of snapping pes anserinus syndrome. Many patients report a transient increase in pain after this injection technique. Infection, although rare, can occur, and careful attention to sterile technique is mandatory.

Clinical Pearls

Snapping pes anserinus syndrome frequently coexists with pes anserine bursitis, arthritis, and internal derangement of the knee, which may require specific treatment to provide palliation of pain and return of function. Injection of local anesthetic and steroid is a safe procedure if careful attention is paid to the clinically relevant anatomy in the areas to be injected. Most side effects of this injection technique are related to needle-induced trauma to the injection site and underlying tissues. The use of physical modalities, including local heat and gentle stretching exercises, should be introduced several days after the patient undergoes this injection technique. Vigorous exercises should be avoided because they would exacerbate the symptoms. Simple analgesics, NSAIDs, and antimyotonic agents may be used concurrently with this injection technique.

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