Posterolateral Corner (PLC) Reconstruction of the Knee

The posterolateral corner is reconstructed when its three static stabilisers are disrupted and the knee is symptomatic. Anatomic reconstruction restores the lateral collateral ligament (LCL), popliteus tendon and popliteofibular ligament (PFL) — the structures that resist varus and external rotation. Missed grade III PLC injury is the most common cause of cruciate graft failure, so identifying and reconstructing it is as important as the cruciate itself. 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 the 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
• High-demand pivoting or cutting athlete with 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; severe arthrofibrosis or range of motion less than 90 degrees flexion Confirm the injury before you cut. The decision rests on three tests. The dial test is performed prone at 30 and 90 degrees of flexion — a side-to-side external rotation difference greater than 10 degrees at 30 degrees alone confirms isolated grade III PLC injury, while a difference at both 30 and 90 degrees indicates combined PLC plus PCL injury. Varus stress radiographs at 20 degrees flexion with greater than 2.5 mm side-to-side difference or greater than 4 mm absolute opening confirm grade III LCL/PLC injury. The external rotation recurvatum test with a heel-height difference greater than 2 cm indicates significant PLC laxity. Obtain full-length standing hip-knee-ankle radiographs in every chronic case to assess alignment. Anatomic versus non-anatomic — the technique choice. Every reconstruction must decide between a true anatomic restoration and a simpler non-anatomic sling.

Correct chronic varus first. 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 — it is mandatory when the mechanical axis falls medial to the medial tibial spine, performed before or concurrent with the ligament reconstruction. 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 the possible need for osteotomy in chronic varus. Setup. General or spinal anaesthesia with a regional block for postoperative analgesia; a popliteal fossa catheter for 48-hour infusion is useful in complex multi-ligament cases. Graft is Achilles tendon allograft (preferred for size and strength) or ipsilateral/contralateral semitendinosus autograft, 7-9 mm in diameter for each limb — two grafts or a single bifurcated graft may be used.

The goal: through the posterolateral exposure, identify and protect the common peroneal nerve, expose the fibular head and lateral femoral condyle, create fibular, tibial and two femoral tunnels, pass and tension graft limbs to restore all three static restraints, then fix the cruciates last. The exposure and nerve protection are laid out in full as the first steps below — this is the heart of the operation.

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Rehabilitation | Phase | Timing | Weight bearing & brace | Motion & strengthening | |---|---|---|---| | 1 — Protection | 0-6 weeks | Touch-down weight bearing with crutches (longer if osteotomy performed); hinged brace locked in extension for 2 weeks then unlocked, worn at all times except therapy | Passive and active-assisted flexion to 90 degrees by week 4; full extension maintained; quad sets, straight-leg raises, ankle pumps; no active hamstring contraction for 6 weeks | | 2 — Motion & strength | 6-12 weeks | Progress to full weight bearing at 6-8 weeks if radiographic healing confirmed; wean daytime brace 8-10 weeks, continue night brace to 12 weeks | Advance to full flexion by 8-10 weeks; closed-chain exercises, stationary bike, leg press; avoid open-chain hamstring work until 4 months | | 3 — Functional | 3-6 months | Full weight bearing | Progressive resistance, single-leg squats, proprioceptive training; initiate straight-line jogging at 4-5 months if strength and stability allow | | 4 — Return to sport | 6-9 months | Full | Cutting, pivoting and contact drills from 6-9 months; full return 9-12 months for contact or pivoting sports when strength symmetry is greater than 90 percent and the dial test is negative | 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). Complications

The three static stabilisers. Modern anatomic reconstruction is built on the quantitative anatomy of the posterolateral corner. The three primary static restraints and their attachments are:

Dynamic stabilisers. The popliteus muscle, biceps femoris, lateral gastrocnemius head and iliotibial band provide dynamic posterolateral stability and must be protected during exposure. Common peroneal nerve course. The nerve emerges from posterior to the biceps femoris tendon about 2 cm proximal to the fibular head, winds around the fibular neck, and divides into deep and superficial peroneal nerves within the peroneal compartment. In acute injuries it may be stretched or contused; in chronic cases it is often encased in dense scar requiring neurolysis — which is why identification and decompression are mandatory steps of the operation. Why anatomic reconstruction matters. Non-anatomic fibular-based techniques (Larson figure-of-eight) restore only two of the three static stabilisers and do not address the popliteofibular ligament's contribution to external rotation control at 60-90 degrees. The LaPrade anatomic technique, with separate femoral tunnels for the LCL and popliteus plus fibular and tibial tunnels, restores near-native varus and rotational stability in biomechanical studies, and in combined ACL-PLC injuries it 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.