Can I refer a patient with painful multiple fluid collections in the posterior knee directly to orthopedics (ortho) or is an MRI recommended first?

From the Guidelines

For a patient with painful multiple fluid collections in the posterior knee, I recommend obtaining an MRI before referring to orthopedics. While you can refer directly to orthopedics, having MRI results available will likely expedite proper treatment planning and may prevent an additional appointment. The MRI will help characterize the fluid collections, which could represent Baker's cysts, ganglion cysts, bursitis, or more concerning conditions like synovial sarcoma. The imaging will reveal important details about the fluid collections' relationship to surrounding structures, any communication with the joint space, and potential underlying causes such as meniscal tears or arthritis. When ordering the MRI, specify "with contrast" if infection or malignancy is suspected, as recommended by the American College of Radiology Appropriateness Criteria 1.

Some key points to consider:

• The American College of Radiology Appropriateness Criteria suggest that MRI is usually appropriate for the evaluation of chronic knee pain, especially when the initial radiographs are normal or demonstrate a joint effusion 1.
• MRI can detect various conditions, including osteoarthritis, meniscal tears, and ligamentous injuries, which may be associated with fluid collections in the posterior knee 1.
• While ultrasound can be used to evaluate fluid collections, MRI provides more detailed information about the surrounding structures and potential underlying causes 1.
• Conservative measures, such as rest, ice, compression, elevation, and over-the-counter anti-inflammatories, can be used for pain management while waiting for orthopedic evaluation, unless contraindicated 1.
• If the patient has severe pain, limited mobility, signs of infection, or rapidly enlarging collections, expedited orthopedic referral is warranted regardless of MRI status 1.

It's essential to note that the most recent and highest-quality study, 1, supports the use of MRI in evaluating knee pain and fluid collections, making it a crucial diagnostic tool in this scenario.

From the Research

Diagnosis and Treatment of Posterior Knee Fluid Collections

• The presence of multiple fluid collections in the posterior knee can be indicative of various conditions, including Baker's cysts, which are often associated with knee joint disorders 2.
• A study published in 2007 found that arthroscopic surgery can be an effective treatment for symptomatic Baker's cysts, with 96% of patients showing clinical improvement and 64% experiencing disappearance of the cyst on MRI 2.
• However, the decision to refer a patient directly to orthopedics (ortho) or to recommend an MRI first depends on the specific clinical presentation and the suspected underlying cause of the fluid collections.

Role of MRI in Diagnosis and Treatment

• MRI can be a useful diagnostic tool in evaluating knee injuries and internal derangement, particularly in cases where the diagnosis is uncertain or the patient has a complex presentation 3, 4.
• A study published in 1999 found that MRI altered the treatment plan in 21% of patients with knee injuries, particularly in cases involving meniscal tears or chondral pathology 3.
• Another study published in 2004 found that the presence of joint fluid on MRI was correlated with internal derangement, but that some knees with no significant effusion may still exhibit internal derangement 4.

Treatment Options for Baker's Cysts

• Sclerotherapy and therapeutic injection with corticosteroids and anesthetics have been shown to be effective in reducing pain symptoms in patients with Baker's cysts 5, 6.
• A case series published in 2023 found that ultrasound and fluoroscopic-guided aspiration followed by therapeutic injection with Depomedrone and Bupivacaine led to a durable reduction in pain symptoms in a majority of patients with symptomatic Baker's cysts 6.

Referral to Orthopedics

• While MRI can be a useful diagnostic tool, it may not always be necessary before referring a patient to orthopedics, particularly in cases where the clinical presentation is suggestive of a Baker's cyst or other condition that can be treated with injection or aspiration 2, 6.
• Ultimately, the decision to refer a patient to orthopedics or to recommend an MRI first should be based on the individual patient's clinical presentation and the suspected underlying cause of the fluid collections, as well as consultation with an orthopedic specialist 3.