What are the diagnosis and treatment options for a patient presenting with a meniscal injury?

Meniscal Injuries: Diagnosis and Treatment

Diagnostic Approach

MRI is the gold standard imaging modality for diagnosing meniscal tears after negative radiographs, with 96% sensitivity and 97% specificity for detecting meniscal injuries. 1

Initial Clinical Assessment

• Obtain radiographs first to rule out fractures and assess for joint effusion, as knee effusion >10 mm on lateral radiograph in patients <40 years with acute knee injury should prompt MRI consideration 1
• Look for specific clinical findings: joint line tenderness, knee effusion, mechanical symptoms (clicking, catching, or true locking), and positive McMurray or Apley maneuvers 2, 3
• Distinguish true mechanical locking (inability to fully extend the knee due to displaced meniscus fragment) from pseudo-locking (intermittent catching sensations), as only true locking indicates obstructing displaced tear requiring surgery 4, 5

MRI Imaging Specifications

• Both 1.5T and 3T MRI protocols have similar high sensitivity and specificity for meniscal tears, so routine 3T is not necessary 1
• MRI should be performed within 6 weeks of acute trauma when possible, as some injuries may become less visible with chronicity 1
• MRI can change management from surgical to conservative in up to 48% of patients presenting with locked knee 1

Alternative Imaging Modalities

• Ultrasound has limited utility for meniscal evaluation, with 85% sensitivity and 86% specificity (highest in recent injuries <1 month), but cannot visualize cruciate ligaments or portions of menisci adequately 1
• SPECT/CT is not recommended as it shows lower sensitivity, specificity, and accuracy than MRI for evaluating meniscal injuries 1

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Treatment Algorithm: The Critical Distinction

The single most important factor determining treatment is whether the meniscal tear is traumatic or degenerative, as traumatic tears require arthroscopic surgery while degenerative tears must be managed conservatively with physical therapy, avoiding surgery entirely. 4

Traumatic Meniscal Tears (Surgical Indication)

Arthroscopic surgery is first-line treatment for traumatic meniscal tears, particularly bucket-handle tears in younger patients, because delayed treatment can cause cartilage damage. 4, 6

Identifying Traumatic Tears:

• Acute onset after significant knee trauma (twisting injury, sports injury, fall) 4
• Bucket-handle tear pattern on MRI causing true mechanical locking 4, 6
• Younger patient age (typically <35 years) 4, 6
• Association with ACL injuries 4
• True mechanical locking: inability to fully extend the knee due to displaced meniscus fragment blocking joint motion 6, 5

Surgical Management:

• Meniscal repair is superior to partial meniscectomy with better functional outcomes and less severe degenerative changes over time 7
• Partial meniscectomy may be performed for non-repairable tears in non-vascularized zones 2
• Recovery timeline: 2-6 weeks with at least 1-2 weeks off work depending on job demands 4, 6, 5

Post-Surgical Rehabilitation:

• Early mobilization to reduce pain and improve function 4, 6
• Structured physical therapy focusing on quadriceps and hamstring strengthening 4, 6
• Avoid complete immobilization to prevent muscular atrophy 6
• NSAIDs (oral or topical) for pain management 6
• Cryotherapy applied through wet towel for 10-minute periods to reduce pain and swelling 6

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Degenerative Meniscal Tears (Conservative Management ONLY)

For degenerative meniscal tears in patients over 35, arthroscopic surgery is explicitly NOT recommended and provides no clinically meaningful improvement in long-term pain or function compared to conservative treatment. 4, 5

Identifying Degenerative Tears:

• Age over 35 years 4, 5
• Insidious onset without major trauma 4
• Imaging evidence of osteoarthritis or chondral thinning 5
• Presence of clicking, catching, or pseudo-locking (these mechanical symptoms respond equally well to conservative treatment and do NOT indicate need for surgery) 5

Conservative Management Protocol:

• Structured physical therapy and exercise therapy for at least 3-6 months as first-line treatment 5
• Quadriceps and hamstring strengthening exercises 5
• Weight loss for overweight patients, which can significantly reduce knee pain and improve function 5
• Activity modification to reduce mechanical stress on the knee 5
• NSAIDs for pain management 5
• Intra-articular corticosteroid injections may be considered if inadequate response after 3 months of conservative management 5

Why Surgery Fails in Degenerative Tears:

• Less than 15% of patients experience small, temporary improvements at 3 months that completely disappear by 1 year 5
• No long-term benefit over conservative treatment for pain or function 5
• Recovery burden includes 2-6 weeks of limited function, inability to bear full weight for up to 7 days, and minimum 1-2 weeks off work 5
• Increased risks including anesthetic complications, infection, and thrombophlebitis 5

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Critical Pitfalls to Avoid

• Do NOT treat all meniscal tears the same way regardless of tear pattern or patient characteristics 4, 6
• Do NOT assume guidelines for degenerative meniscal tears apply to traumatic bucket-handle tears 4, 6
• Do NOT rush to surgery based on MRI findings alone in patients over 35, as degenerative changes are common age-related findings that do not benefit from surgery 4, 5
• Do NOT interpret clicking, catching, or intermittent "locking" sensations as indication for surgery in degenerative tears, as these mechanical symptoms respond equally well to conservative treatment 5
• Do NOT delay treatment for true locked knees (traumatic tears with inability to fully extend), as this can lead to cartilage damage 4, 6
• Do NOT assume prior arthroscopy indicates need for repeat surgery in patients with progressive degenerative changes, as the underlying disease process will not be altered by additional surgery 5