What is the best course of treatment for a patient experiencing pain on the right knee radiating to the lower leg and back?

Right Knee Pain Radiating to Lower Leg and Back: Diagnostic and Treatment Approach

Begin with plain radiographs (AP, lateral, tunnel, and tangential patellar views) as your first imaging study, but critically important—you must evaluate for referred pain from the lumbar spine or hip before attributing all symptoms to knee pathology, especially given the radiating pattern to the back. 1, 2

Critical First Step: Rule Out Referred Pain

The radiation of pain to both the lower leg AND back is a red flag that demands evaluation beyond the knee itself:

• Lumbar spine pathology must be considered as a primary source when knee radiographs are unremarkable and pain radiates to the back, as the American College of Radiology explicitly warns against overlooking this pattern 2
• Hip pathology can refer pain to the knee and should be evaluated with dedicated hip radiographs if knee imaging is unremarkable 3, 2
• Perform a thorough clinical examination of the lumbar spine and hip before rushing to advanced knee imaging 2

Initial Diagnostic Workup

Obtain plain radiographs of the knee first (AP, lateral, tunnel/Rosenberg, and tangential patellar views) regardless of whether pain is acute or chronic 1

Key physical examination findings to document:

• Joint line tenderness, patellar tenderness, and fibular head tenderness 1
• Mechanical symptoms (locking, catching, popping, giving way) suggesting meniscal pathology 1
• Ability to flex knee to 90° and weight-bearing status (inability to take 4 steps requires imaging) 1
• Range of motion of lumbar spine and hip to assess for referred pain sources 2

When to Proceed to Advanced Imaging

Order MRI of the knee without IV contrast when:

• Radiographs are normal or show only joint effusion but pain persists despite conservative treatment 1
• Clinical suspicion exists for meniscal tear, ligament injury, or occult fracture 1
• You have ruled out lumbar spine and hip as pain sources 2

Important caveat: Approximately 20% of patients inappropriately receive MRI without recent radiographs—don't skip the plain films 1. Additionally, meniscal tears are incidental findings in the majority of patients >70 years and equally common in painful and asymptomatic knees in patients 45-55 years 1

If Knee Imaging is Unremarkable

Consider lumbar spine imaging given the radiation to the back:

• The American College of Radiology specifically recommends evaluating the lower back when knee radiographs are unremarkable but symptoms persist with a radiating pattern 2
• In pediatric patients, spondylolysis can present with low back pain radiating to the leg with positive straight leg raising 4

Initial Treatment Strategy

Start with non-pharmacologic treatments as first-line therapy, as strongly recommended by the American College of Rheumatology 1:

• Exercise therapy (hip and knee strengthening if anterior knee pain pattern) 1, 5
• Aquatic exercise 1
• Weight loss if overweight 1
• Self-management programs and patient education 1

Pharmacologic options (use lowest effective dose for shortest duration) 1, 6:

• Topical NSAIDs as initial choice 1
• Oral NSAIDs: Ibuprofen 400 mg every 4-6 hours as needed (do not exceed 3200 mg daily; take with meals or milk to reduce GI complaints) 6
• Acetaminophen 1
• Tramadol for more severe pain 1
• Intra-articular corticosteroid injections 1

Avoid: Glucosamine, chondroitin sulfate, and topical capsaicin (conditionally recommended against) 1

Common Pitfalls to Avoid

• Most critical error: Assuming the knee is the pain source without evaluating lumbar spine and hip, especially with radiating symptoms 2
• Ordering MRI before obtaining plain radiographs 1
• Assuming all meniscal tears seen on MRI are symptomatic, particularly in patients >45 years 1
• Rushing to surgery for degenerative meniscal tears—exercise therapy is first-line even with mechanical symptoms 7
• Not documenting laterality specifically (use "right knee" rather than unspecified codes) 3

Treatment Duration Expectations

• Conservative management should be tried for at least 3 months before considering other treatment options 5
• Therapeutic response is sometimes seen in a few days to a week but most often by two weeks for inflammatory conditions 6
• For patellofemoral pain, hip and knee strengthening exercises combined with foot orthoses or patellar taping are recommended with no indication for surgery 7