MCL & PMC Injuries

Anatomy

MCL

  • Superficial Layer:
    • Fan-shaped.
    • One origin and two insertion points.
    • More important for valgus stability.
  • Deep Layer:
    • Thickening of the medial capsule.
    • Connected to the medial meniscus (MM) by coronary ligaments.
    • Origin: Medial epicondyle of femur (adductor tubercle).
    • Insertion: Anteromedial tibia, deep to the pes anserinus tendons.

Blood Supply

  • Superomedial and inferomedial geniculate arteries.

Medial Complex

  • Composed of 3 layers of static and dynamic stabilizers.

Static Stabilizers:

  • Superficial MCL (primary restraint to valgus).
  • Posterior Oblique Ligament.
  • Deep MCL.

Dynamic Stabilizers:

  • Semimembranosus (5 insertion points).
  • Pes Anserinus Tendons (Sartorius, Gracilis, Semitendinosus).
  • Medial Retinaculum, VMO.

Layered Structure:

Layer Contents
Layer 1 Patella Retinacular fascia, Sartorius & Sartorius Fascia, Semitendinosus, Gracilis
Layer 2 Superficial Medial Collateral, POL
Layer 3 Semimembranosus (5 insertions), Medial Capsule, Deep MCL

Pes Anserinus

  • Overlies the MCL.
  • Pneumonic SGT FOT (Sartorius, Gracilis, Semitendinosus).
    • Sartorius (femoral nerve).
    • Gracilis (obturator nerve).
    • Semitendinosus (tibial branch of the sciatic nerve).

Biomechanics

  • MCL is the primary restraint to valgus.
  • Other ligaments and structures act as secondary static or dynamic stabilizers.

Injury Mechanism

  • MCL is the most commonly injured knee ligament.
  • Valgus force.
  • Injury is usually to femoral origin.

Concurrent Injuries

  • ACL is the most common concurrent injury.
  • Found in 75% of grade 3 MCL injuries.

Examination

  • Valgus instability in 30° flexion indicates isolated MCL.
  • Valgus instability in extension indicates grade 3 MCL with possible other ligament injury (e.g., ACL).
  • Pivot Shift Test:
    • Used to rule out ACL.
    • False negative in grade 3 MCL.
    • Based on joint pivoting and subluxation around an intact MCL.

Classification

  • Based on degree of valgus laxity:
    • Grade 1: Sprain with no laxity.
    • Grade 2: Partial injury with laxity but with end point.
    • Grade 3: Complete injury with >10mm joint opening.
  • Grade 3 isolated MCL is rare.
  • Chronic MCL: Seen on X-ray as Pelligrini-Steida sign (ossification at MCL femoral origin).

Management

Non-operative Management

  • Almost all MCL injuries are managed non-operatively.
  • Brace for grade 2 and 3 injuries.
  • RICE (Rest, Ice, Compression, Elevation).
  • ROM and early weight-bearing.
  • Graded return to sports.

Operative Management

  • Failed non-operative management.
  • Chronic symptomatic MCL instability.
  • Acute MCL injuries with ligament flipped into the joint.
  • Multi-ligament instability: MCL can sometimes be left alone.

Surgical Technique

Acute Injury:

  • Proximal avulsion: Use anchors in the medial epicondyle.
  • Direct repair for intrasubstance tears.
  • May need to advance MCL and POL if tissue is insufficient.

Chronic Injury:

  • More common scenario.
  • Advancement may not be possible.
  • Reconstruct using ST autograft or allografts at isometric points through tunnels.

Management of Combined ACL and MCL Injury

  • Rule: Wait for MCL healing (6-8 weeks) before addressing ACL reconstruction.
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