Epidemiology & Risk Factors

Demographics:
- Young, active athletes: Acute traumatic injuries (rotational force on a planted foot).
- Older adults (>40-50 yo): Degenerative tears with minimal/trivial trauma (e.g., squatting, rising from a chair).
Anatomy:
- Medial meniscus > lateral meniscus tears (medial is less mobile and anchored to the MCL).
- Associated with concurrent ACL tears (e.g., “unhappy triad”: ACL, MCL, medial meniscus).

Clinical Features

History:
- Acute onset with a twisting mechanism on a flexed, weight-bearing knee.
- Sensation of a “pop” followed by delayed joint swelling/effusion (develops over 12–24 hours; vs immediate hemarthrosis in ACL tears).
- Mechanical symptoms: Intermittent catching, clicking, or locking; feeling of knee “giving way” or instability.
Physical Exam:
- Joint-line tenderness: High sensitivity; localized to the medial or lateral joint line.
- Effusion/mild joint swelling.
- Provocative Maneuvers:
  - McMurray test: Palpable or audible “click” / pain during passive knee flexion-extension with internal/external rotation.
  - Thessaly test: Pain or catching while standing on the affected leg (flexed at 20°) and rotating the knee internally and externally.
  - Apley grind test: Pain on axial compression and tibial rotation with pt in prone position (flexed 90°).

Initial / Screening:
- Plain Radiographs (XR) (AP, lateral, sunrise, and weight-bearing views):
  - Usually normal in acute tears.
  - Performed first to rule out fractures, loose bodies, or underlying OA.
Confirmatory / Non-invasive Gold Standard:
- MRI of the knee: Test of choice; demonstrates high-signal intensity extending through the meniscal surface.
Definitive (Invasive):
- Diagnostic Arthroscopy: Reserved for cases planned for simultaneous therapeutic intervention.

ACL Tear:
- Diff by: Immediate gross hemarthrosis (within minutes to hours), rapid onset swelling, (+) Lachman test (most sensitive), (+) Anterior drawer test.
MCL Tear:
- Diff by: Mechanism of pure valgus stress, localized pain at the medial femoral epicondyle, laxity with valgus stress testing at 30° flexion, no mechanical locking.
Patellofemoral Pain Syndrome (PFPS):
- Diff by: Chronic anterior retropatellar pain aggravated by prolonged sitting (“theater sign”) or stair descent, no joint-line tenderness, no true effusion.
Pes Anserine Bursitis:
- Diff by: Pain localized inferior to the medial joint line over the anteromedial proximal tibia, normal range of motion (ROM), no mechanical locking or intra-articular effusion.
Knee Osteoarthritis (OA):
- Diff by: Insidious onset, age >50 yo, morning stiffness <30 min, crepitus, XR showing asymmetric joint space narrowing and osteophytes.

First-line (Conservative Therapy):
- Indications: Degenerative tears in older pts, mild/infrequent symptoms, stable tears without mechanical locking.
- Regimen:
  - RICE (Rest, Ice, Compression, Elevation) + activity modification.
  - NSAIDs for pain/inflammation.
  - Physical therapy (PT) focused on quadriceps and hamstring strengthening.
Second-line / Surgical Intervention:
- Indications: Persistent symptoms after 4–6 weeks of conservative therapy, younger/active athletic pts with acute tears, or persistent “locked knee” (mechanical obstruction).
- Procedures:
  - Arthroscopic Meniscal Repair: Preferred for peripheral (“red-red” zone) tears due to good vascularity and high healing potential.
  - Partial Meniscectomy: Performed for avascular (“white-white” central zone) or complex/macerated tears that cannot heal.

Early accelerated knee osteoarthritis (esp. post-meniscectomy due to altered load transmission).
Chronic articular cartilage erosion/chondral defects.
Baker cyst (popliteal cyst) formation secondary to chronic joint effusion.
Arthrofibrosis or persistent joint stiffness post-op.

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