Posterior Approach to the Knee (Popliteal Fossa)

What it exposes. The posterior (popliteal) approach gives direct, central access to the posterior capsule of the knee, the tibial insertion of the posterior cruciate ligament, the contents of the popliteal fossa, and the posterior aspect of the distal femur and proximal tibia. It is the only approach that exposes the true posterior knee — no anterior or side approach can match it. Why posterior. Most knee pathology is anterior and is managed arthroscopically or through anterior approaches. The posterior approach is reserved for pathology that genuinely lies behind the knee — behind the posterior capsule, at the PCL tibial insertion, or within the popliteal fossa itself. Most PCL avulsions, loose bodies and synovitis are now managed arthroscopically, so the open posterior approach is reserved for large displaced avulsions needing solid fixation, cysts that have failed arthroscopic management, tumours and vascular cases where open control is mandatory. Position & landmarks. Position the patient fully prone on a radiolucent table. Pad all pressure points meticulously (face and eyes, chest, breasts, genitalia, knees, dorsum of feet), place the arms at less than 90 degrees of abduction and padded to protect the brachial plexus, and confirm C-arm access before prepping. Flex both knees 10 to 15 degrees over a small bolster — this relaxes the gastrocnemius and gently lifts the popliteal neurovascular bundle away from the capsule. Apply a high thigh tourniquet for a bloodless field, but leave the limb perfused when vascular repair is anticipated.

The popliteal fossa is a diamond-shaped depression whose borders define the safe surgical field: - Superolateral border — biceps femoris tendon

• Superomedial border — semimembranosus, overlapped by semitendinosus
• Inferolateral border — lateral head of gastrocnemius
• Inferomedial border — medial head of gastrocnemius
• Floor (deep) — popliteal surface of the femur, the posterior capsule, the oblique popliteal ligament, and the popliteus fascia over popliteus
• Roof (superficial) — skin, subcutaneous fat, and the tough popliteal fascia The palpable landmarks are the biceps femoris tendon (the common peroneal nerve lies along its medial border), the medial hamstrings, the two heads of gastrocnemius (the key deep interval runs between them), and the popliteal skin crease — which the incision must cross obliquely, never transversely. Indications.
• PCL tibial avulsion fractures requiring open reduction and internal fixation of a large displaced bony fragment
• Tibial spine (eminentia) avulsion fractures that are posteriorly based and not amenable to arthroscopic fixation
• Popliteal (Baker) cyst excision when large, symptomatic, or recurrent after treatment of the intra-articular cause
• Posterior capsular repair or capsulorrhaphy for posterior capsular deficiency
• Removal of posterior loose bodies not reachable arthroscopically
• Excision of posterior tumours of the distal femur or proximal tibia (osteochondroma, soft tissue tumour)
• Popliteal vascular exposure for repair (frequently shared with a vascular team)
• Posterior synovectomy for diffuse pigmented villonodular synovitis or synovial chondromatosis Contraindications.
• Pathology that can be reached arthroscopically or through a simpler anterior approach
• Inability to tolerate the prone position (severe cardiopulmonary disease, spinal instability, late pregnancy)
• Compromised posterior skin (open wound, deep abrasion, previous posterior incision with poor healing)
• An isolated PCL substance tear (managed arthroscopically or via an inlay technique rather than an open popliteal approach) Alternatives and variants. Arthroscopic PCL reconstruction or tibial avulsion fixation is the default for most PCL pathology and avoids an open posterior approach entirely. The posteromedial (Burks) approach (knee flexed and externally rotated, medial to the gastrocnemius) is excellent for PCL tibial avulsion and inlay reconstruction without full prone positioning. A posterolateral approach serves the posterolateral corner, and a medial popliteal approach gives isolated vascular access above the knee.

Work prone through the popliteal fossa, protecting the sural nerve and short saphenous vein superficially, then developing the interval between the two heads of gastrocnemius to reach the posterior capsule. Find the tibial nerve first — it is the safest landmark — and the vein and artery fall into order deep to it.

Structures at risk, by layer

Neurovascular injury management. Arterial injury is limb-threatening: apply direct pressure, gain proximal and distal control, involve vascular surgery, and repair or interposition-graft. Nerve injury (tibial or common peroneal): document baseline function, explore if transected with primary repair or graft, and observe a neurapraxia. Venous injury: repair where possible to limit deep vein thrombosis risk and anticoagulate postoperatively. Extensile options. Extend proximally up the posterior thigh along the biceps femoris to expose the distal sciatic nerve, the femoral segment of the popliteal artery, and the posterior distal femur (the route for sciatic nerve exploration and posterior distal femoral tumour excision). Extend distally down the posteromedial calf, developing the plane between gastrocnemius and soleus — this becomes the posterior approach to the tibia, exposing the posterior tibial neurovascular bundle and posterior tibial surface. The posteromedial (Burks) variant — knee flexed and externally rotated rather than fully prone, interval between semimembranosus and the medial head of gastrocnemius — is preferred by many for isolated PCL tibial avulsion and inlay reconstruction.

Closure. Close in layers with the knee slightly flexed to relieve tension across the crease; repair the posterior capsule if opened; reattach any detached gastrocnemius head; re-approximate the popliteal fascia to restore the barrier over the neurovascular bundle; subcuticular skin closure for the best cosmetic result; drain only if a significant dead space remains. Complications.

• PCL reconstruction and PCL tibial avulsion ORIF — direct visualisation and screw or suture-bridge fixation of a displaced bony avulsion.
• Tibial spine (eminentia) avulsion ORIF for posteriorly based fragments not amenable to arthroscopy.
• Popliteal (Baker) cyst excision with capsular closure and treatment of the underlying intra-articular cause.
• Posterior capsular repair for traumatic or iatrogenic capsular deficiency.
• Posterior loose body removal and posterior synovectomy.
• Excision of posterior osteochondroma or soft tissue tumour of the distal femur or proximal tibia.
• Popliteal artery repair and tibial nerve exploration in the fossa.

Guidelines, registries & global practice The posterior approach to the knee is taught worldwide as a standard operative exposure. Its anatomy and the safe interval-based dissection are described consistently across the major surgical exposure textbooks, and practice converges on a few principles: prone positioning for the classic approach, a lazy-S rather than transverse incision, identification of the superficial sural nerve and short saphenous vein, and protection of the popliteal bundle whose artery lies deepest on the capsule.

Registry and population evidence. Vascular injury complicates a substantial minority of knee dislocations; a hard sign of ischaemia mandates immediate exploration, and CT angiography is reserved for the equivocal, stable patient. Most popliteal (Baker) cysts are associated with an intra-articular lesion (meniscal or chondral), which underpins the principle of treating the underlying cause rather than the cyst alone. Global practice variation. In well-resourced settings, arthroscopic management of PCL avulsions, loose bodies and cysts has markedly reduced the use of the open posterior approach, which is now reserved for specific indications. In resource-limited settings the open approach retains a larger role because arthroscopic capacity may be constrained, but the same anatomical and safety principles apply. Consent (globally applicable). Discuss popliteal vascular injury (limb-threatening), tibial and common peroneal nerve injury, wound breakdown, deep vein thrombosis, stiffness and the importance of avoiding a transverse crease incision, and recurrence when the underlying intra-articular cause is not addressed.