What is the prognosis for an adult patient with a medial meniscus injury after arthroscopy, assuming no significant medical history?

Prognosis of Medial Meniscus Injury After Arthroscopy

The prognosis after arthroscopic surgery for degenerative medial meniscus tears is generally poor for long-term pain relief and functional improvement, with most patients experiencing no sustained benefit beyond one year, though approximately 80% of patients may report subjective improvement in carefully selected acute traumatic cases. 1

Context-Dependent Outcomes

The prognosis fundamentally depends on whether the meniscus injury is degenerative versus acute traumatic:

Degenerative Meniscus Tears (Age >35, Non-Traumatic)

For degenerative tears, arthroscopy provides minimal to no long-term benefit:

• Less than 15% of patients experience small or very small improvements in pain or function at 3 months post-surgery, and this benefit does not persist at one year. 1

• Most patients (the majority) will experience important improvement in pain and function WITHOUT arthroscopy, as degenerative knee disease symptoms naturally fluctuate and tend to improve over time after initial physician consultation. 1

• The BMJ clinical practice guideline makes a strong recommendation AGAINST arthroscopy for degenerative knee disease, including those with meniscal tears, mechanical symptoms, or sudden non-traumatic symptom onset. 1

• This applies to patients with or without radiographic osteoarthritis, as trials showed similar poor effect sizes regardless of radiographic findings. 1

Acute Traumatic Tears (Younger Patients, Sports Injuries)

For acute trauma-related tears in well-selected cases, prognosis is considerably better:

• Approximately 80% of patients report good or excellent subjective outcomes after arthroscopic partial meniscectomy for acute traumatic tears. 2, 3

• Mean pain scores (VAS) improve from 5.6 preoperatively to 2.3 at 4-year follow-up, and Lysholm scores improve from 43 to 72.7 points. 4

• At 6 months post-surgery, approximately 92.5% of patients with acute tears report good or excellent subjective outcomes. 5

Prognostic Factors That Predict Poor Outcomes

Even in acute traumatic cases, specific factors predict worse prognosis:

• Body Mass Index ≥26 kg/m² is a major predictor of poor outcome. 4

• Outerbridge grade III or IV chondral lesions of the medial compartment significantly worsen prognosis. 4

• Degenerative changes in patellofemoral joint surfaces predict worse outcomes. 4

• Varus limb alignment (hip-knee-ankle angle >5°) correlates with poor results. 4

• Smoking is strongly associated with treatment failure. 2

• Kellgren-Lawrence grade 2 osteoarthritis predicts poor surgical outcomes. 2

• ACL insufficiency (partial rupture or degenerative laxity) worsens prognosis. 4

Recovery Timeline and Burden

Regardless of outcome, all patients face significant recovery burden:

• Recovery typically requires 2-6 weeks, during which patients experience pain, swelling, and limited function. 1

• Patients cannot bear full weight for 2-7 days post-operatively (requiring crutches). 1

• Return to work takes 1-2 weeks for sedentary jobs, at least 6 weeks for physical jobs. 1

• Driving is limited for approximately 1-3 weeks after the procedure. 1

Special Considerations

The only potential exception to poor prognosis in degenerative disease:

• Patients who are objectively unable to fully extend their knee (true locked knee) may potentially benefit, though this remains unproven by high-quality evidence. 1

• Meniscus root repairs (not simple partial meniscectomy) demonstrate superior outcomes with approximately 80% success rates at 2 years and better long-term functional outcomes compared to debridement. 6

Common Pitfalls to Avoid

Critical errors that worsen patient outcomes:

• Performing arthroscopy on degenerative tears without adequate trial of conservative management (exercise therapy, weight loss, physical therapy) exposes patients to surgical risks without benefit. 7

• Assuming mechanical symptoms or meniscal tears on MRI indicate surgical necessity - meniscal tears are common incidental findings in older patients and rarely cause symptoms. 1

• Operating on patients with multiple poor prognostic factors (obesity, smoking, varus alignment, advanced chondral damage) leads to predictable failure. 2, 4

• Failing to counsel patients that natural history favors improvement without surgery in degenerative cases. 1