Posterolateral Corner (PLC) Reconstruction of the Knee

Surgical Indications

Absolute Indications

• Grade III PLC injury with symptomatic varus instability or thrust gait
• Combined cruciate and PLC injury requiring multi-ligament reconstruction
• Failed cruciate reconstruction secondary to untreated PLC insufficiency
• Chronic PLC injury with greater than 10 degrees side-to-side external rotation difference on dial test

Relative Indications

• Grade II PLC injury with persistent functional instability after 3-6 months of rehabilitation
• Varus alignment greater than 5 degrees with medial compartment overload symptoms
• Patient with high-demand pivoting or cutting sports and documented grade III laxity

Contraindications

Absolute:

• Active knee infection or septic arthritis
• Uncontrolled medical comorbidities precluding major surgery
• Non-ambulatory patient with minimal functional demand

Relative:

• Acute grade I-II PLC injury (trial of non-operative management first)
• Isolated grade II injury without thrust or giving-way symptoms
• Severe arthrofibrosis or limited range of motion less than 90 degrees flexion

Evidence for Anatomic Reconstruction

Why Anatomic Reconstruction Matters

• Non-anatomic fibular-based techniques (Larson figure-of-8) restore only two of the three static stabilisers and do not address the popliteofibular ligament contribution to external rotation control at 60-90 degrees.
• LaPrade anatomic technique with separate femoral tunnels for LCL and popliteus plus fibular and tibial tunnels restores near-native varus and rotational stability in biomechanical studies.
• In combined ACL-PLC injuries, anatomic PLC reconstruction reduces ACL graft forces by 30-40 percent compared with non-anatomic techniques.

Combined Osteotomy Evidence

• Chronic varus greater than 5 degrees produces medial compartment overload and accelerates graft failure. Opening-wedge or closing-wedge biplanar osteotomy normalises the mechanical axis and improves ligament reconstruction survival.
• In series of combined osteotomy plus ligament reconstruction, 85-90 percent of patients achieve good or excellent outcomes at 5 years with low revision rates.

Relevant Surgical Anatomy

The Three Static Stabilisers

• Lateral collateral ligament (LCL): Primary varus restraint at 0-30 degrees flexion. Origin 3-4 mm proximal and posterior to lateral epicondyle; insertion on fibular head 8 mm posterior to anterior margin and 14 mm distal to tip. Average length 70 mm.
• Popliteus tendon: Primary external rotation restraint. Origin 11 mm anterior and distal to LCL femoral origin on the lateral femoral condyle; courses posteromedially through the popliteal hiatus to insert on the posterior tibia.
• Popliteofibular ligament (PFL): Primary restraint to posterolateral rotation at 60-90 degrees. Origin at popliteus musculotendinous junction; inserts on posteromedial aspect of fibular styloid 1 cm distal to tip.

Dynamic Stabilisers

• Popliteus muscle, biceps femoris, lateral gastrocnemius head and iliotibial band provide dynamic posterolateral stability. These must be protected during exposure.

Common Peroneal Nerve Course

• Emerges from posterior to biceps femoris tendon 2 cm proximal to fibular head.
• Winds around the fibular neck, divides into deep and superficial peroneal nerves within the peroneal compartment.
• In acute injuries the nerve may be stretched or contused; in chronic cases it is often encased in dense scar requiring neurolysis.

Posterolateral Approach

Patient Positioning

Supine with leg holder or lateral decubitus with hip flexed 45 degrees and knee flexed 90 degrees. A tourniquet is applied to the thigh but inflated only if needed. The foot is prepped free to allow intraoperative dial testing.

Incision and Exposure

A curvilinear incision is made from the lateral femoral epicondyle distally along the posterior border of the iliotibial band to the fibular head, then extended distally along the posterior border of the biceps femoris. The iliotibial band is split in line with its fibres 2 cm anterior to the lateral intermuscular septum. The biceps femoris is retracted posteriorly to expose the common peroneal nerve.

Nerve Identification and Protection

The common peroneal nerve is identified at the posterior border of the biceps femoris, 2 cm proximal to the fibular head. It is decompressed from the fibular neck to the entrance of the peroneal tunnel and protected with a vessel loop throughout the procedure. Intraoperative nerve stimulation confirms continuity before and after reconstruction.

Fibular Head Exposure

The fibular head is exposed by elevating the peroneal muscles from its anterior surface and the soleus from its posterior surface. The LCL and PFL insertions are identified. A 2.5 mm guide pin is placed from anterolateral to posteromedial through the centre of the fibular head, 1 cm distal to the styloid tip, and confirmed with fluoroscopy.

Femoral Exposure

The lateral epicondyle is palpated. The LCL origin is 3-4 mm proximal and posterior to the epicondyle. The popliteus tendon origin lies 11 mm anterior and distal. Two 2.5 mm guide pins are placed at these sites and over-reamed to 7-8 mm after confirmation of position.

Positioning and Preparation

Patient position: Supine with leg holder allowing full flexion and extension. Foot prepped free for dial testing. Tourniquet on thigh, inflated only for deep dissection if bleeding obscures visualisation.

Anaesthesia: General or spinal with regional block for postoperative analgesia. Consider popliteal fossa catheter for 48-hour infusion in complex multi-ligament cases.

Graft selection: Achilles tendon allograft (preferred for size and strength), or ipsilateral/contralateral semitendinosus autograft. Graft diameter 7-9 mm for each limb. Two grafts or a single bifurcated graft may be used.

Consent: Counsel regarding common peroneal nerve injury (1-3 percent permanent palsy), recurrent instability (5-10 percent), stiffness requiring manipulation (10-15 percent), infection (less than 1 percent), and need for osteotomy in chronic varus.

LaPrade Anatomic Reconstruction — Step-by-Step

Step 1: Diagnostic Arthroscopy and Cruciate Reconstruction

Perform arthroscopy to confirm combined injuries, address meniscal pathology and perform ACL or PCL reconstruction first. Fix cruciate grafts last after PLC fixation to avoid overconstraint.

Step 2: Posterolateral Exposure and Nerve Protection

Make the curvilinear incision, split the iliotibial band, identify and decompress the common peroneal nerve, protect with vessel loop. Expose the fibular head and lateral femoral condyle.

Step 3: Fibular Tunnel Creation

Place a 2.5 mm guide pin from anterolateral to posteromedial through the centre of the fibular head, exiting 1 cm distal to the styloid tip. Confirm position with anteroposterior and lateral fluoroscopy. Over-ream to 6-7 mm. Pass a passing suture.

Step 4: Tibial Tunnel Creation (for PFL limb)

Identify Gerdy's tubercle. Place a 2.5 mm guide pin 1 cm distal and medial to the tubercle, aimed 60 degrees distal and 20 degrees medial, exiting the posteromedial tibia 1 cm distal to the joint line. Confirm with lateral fluoroscopy to avoid popliteal vessels. Over-ream to 7 mm.

Step 5: Femoral Tunnel Creation

Identify the LCL origin 3-4 mm proximal and posterior to the lateral epicondyle. Place a 2.5 mm pin aimed 35-40 degrees anterior and proximal. Identify the popliteus origin 11 mm anterior and distal to the LCL origin and place a second pin with the same trajectory. Over-ream each to 7-8 mm to a depth of 25 mm. Confirm divergence from any ACL tunnel with fluoroscopy.

Step 6: Graft Passage and Fixation

Pass the LCL graft limb through the fibular tunnel from anterior to posterior and fix to the femoral LCL tunnel with a 7 mm interference screw at 20 degrees flexion and neutral rotation under slight valgus tension. Pass the popliteus/PFL limb through the tibial tunnel and fix to the popliteus femoral tunnel at 60 degrees flexion with slight internal rotation tension. Use cortical button or interference screw fixation on the tibia.

Step 7: Final Tensioning and Cruciate Fixation

Reduce the knee in neutral rotation and slight valgus. Tension and fix the cruciate grafts last. Perform final dial test to confirm restoration of stability. Irrigate, achieve haemostasis and close in layers over a drain.

Post-operative Protocol

Phase 1: Protection (Weeks 0-6)

• Weight bearing: Touch-down weight bearing with crutches for 6 weeks (longer if osteotomy performed)
• Brace: Hinged knee brace locked in extension for 2 weeks, then unlocked for ROM; worn at all times except therapy
• ROM: Passive and active-assisted flexion to 90 degrees by week 4; full extension maintained
• Muscle activation: Quadriceps sets, straight-leg raises, ankle pumps; no active hamstring contraction for 6 weeks
• Analgesia: Multimodal including popliteal catheter for 48-72 hours, NSAIDs, paracetamol

Phase 2: Motion and Strength (Weeks 6-12)

• Weight bearing: Progress to full weight bearing at 6-8 weeks if radiographic healing confirmed
• ROM: Advance to full flexion by week 8-10; maintain full extension
• Strength: Begin closed-chain exercises, stationary bike, leg press; avoid open-chain hamstring work until 4 months
• Brace: Wean daytime brace at 8-10 weeks; continue night brace until 12 weeks

Phase 3: Functional Training (Months 3-6)

• Strength: Progressive resistance, single-leg squats, proprioceptive training
• Cardiovascular: Elliptical, swimming, cycling
• Running: Initiate straight-line jogging at 4-5 months if strength and stability allow
• Agility: Begin at 5-6 months under supervision

Phase 4: Return to Sport (Months 6-9)

• Criteria: Full painless ROM, greater than 90 percent quadriceps and hamstring strength symmetry, negative pivot-shift and dial test, hop test greater than 90 percent symmetry
• Sport-specific drills: Cutting, pivoting, contact drills from month 6-9
• Full return: 9-12 months for contact or pivoting sports; longer if combined osteotomy or multi-ligament reconstruction

Rehabilitation Pearls

• Early quadriceps activation prevents patellar tendon shortening and anterior knee pain
• Avoid active hamstring contraction for 6 weeks to protect the popliteus and PFL grafts
• Serial dial testing at each phase confirms maintenance of stability
• In combined osteotomy cases, delay weight bearing until radiographic union (typically 8-12 weeks)