Surgical Approaches to the Knee
Expose the target, protect the extensor mechanism, close what you release
Approach Families
Critical Must-Knows
- Do not describe a knee approach by incision alone. State position, landmarks, interval, target, danger structures and closure.
- The medial parapatellar approach is extensile and reliable, but the patellar tendon and blood supply must be protected.
- Subvastus and midvastus approaches may preserve extensor mechanism continuity, but exposure is less extensile and patient selection matters.
- Posteromedial approaches risk the saphenous nerve and vein; posterolateral approaches require deliberate common peroneal nerve protection.
- The best approach is the one that reaches the pathology safely without compromising soft-tissue envelope, fixation or later reconstruction.
Clinical Pearls
- "A valgus TKA may need lateral releases or a lateral parapatellar approach when the lateral side is the contracted side.
- "A posteromedial tibial plateau fragment needs a posterior buttress; an anterolateral plate alone may not control it.
- "Common peroneal nerve identification is not optional in posterolateral knee exposure.
- "Closure is part of the approach: arthrotomy, retinaculum, capsule, quadriceps split, subvastus sleeve and released tendons must be restored deliberately.
Do not chase the X-ray through the wrong skin incision
Choose the approach by the structure that needs reduction, fixation, release or reconstruction. A familiar approach becomes unsafe when it cannot reach the target or forces excessive soft-tissue stripping.
At a Glance: Approach Choice
| Clinical Problem | Useful Exposure | Reason |
|---|---|---|
| Routine primary TKA | Medial parapatellar, midvastus or subvastus | Extensor mechanism access, patellar eversion or subluxation, and implant workflow. |
| Stiff, obese, revision or complex TKA | Medial parapatellar with extensile options | Reliable exposure and ability to extend proximally or distally. |
| Valgus TKA with contracted lateral side | Medial approach with lateral releases or lateral parapatellar approach | Approach must allow safe balancing of the contracted side. |
| Posteromedial tibial plateau fragment | Posteromedial approach | Direct reduction and buttress fixation of posterior medial shear. |
| Posterolateral corner reconstruction | Posterolateral approach | Direct access to fibular head, LCL, popliteus and PLC structures. |
PLATEApproach Description
| P | Position Supine, lateral or prone; tourniquet and fluoroscopy plan. |
| L | Landmarks Patella, tibial tubercle, joint line, fibular head and planned incision. |
| A | Access Name the interval or release that reaches the target. |
| T | Threats Patellar tendon, saphenous bundle, common peroneal nerve and skin bridge. |
| E | Exit Close what was opened and document postoperative protection. |
| P | Position Supine, lateral or prone; tourniquet and fluoroscopy plan. | T | Threats Patellar tendon, saphenous bundle, common peroneal nerve and skin bridge. |
| L | Landmarks Patella, tibial tubercle, joint line, fibular head and planned incision. | E | Exit Close what was opened and document postoperative protection. |
| A | Access Name the interval or release that reaches the target. |
Hook:PLATE keeps a knee approach description practical.
FINDPosterolateral Safety
| F | Fibular head Use as the key landmark. |
| I | Identify peroneal nerve Trace and protect it before retraction. |
| N | No blind release Avoid blind biceps, LCL or capsule release. |
| D | Document function Record dorsiflexion and sensation before and after surgery. |
| F | Fibular head Use as the key landmark. | N | No blind release Avoid blind biceps, LCL or capsule release. |
| I | Identify peroneal nerve Trace and protect it before retraction. | D | Document function Record dorsiflexion and sensation before and after surgery. |
Hook:Find the nerve before deep posterolateral work.
Overview and Indications
Knee approaches are chosen by target pathology. The decision is different for total knee arthroplasty, tibial plateau fixation, extensor mechanism repair, multiligament reconstruction, infection washout and revision surgery. A safe answer starts with what must be seen or controlled: the extensor mechanism, medial plateau, posteromedial fragment, lateral plateau, posterolateral corner, patella, distal femur, proximal tibia or prosthetic joint.
Incision is not the approach
An approach is a controlled route: position, landmarks, interval, deep exposure, danger structures, extension options and closure. The skin incision is only the visible start.
Relevant Anatomy
The knee is unforgiving because the soft-tissue envelope is thin, the extensor mechanism is essential for function, and several approaches work close to named nerves and vessels. The approach must preserve skin bridges, protect the patellar tendon insertion, avoid devascularising the patella unnecessarily and respect neurovascular structures.
Extensor Mechanism
Quadriceps tendon, patella, retinaculum and patellar tendon determine exposure and postoperative function. A patellar tendon avulsion is a major complication.
Medial Side
Saphenous nerve and great saphenous vein are at risk around medial and posteromedial exposures. The pes anserinus may need controlled mobilisation.
Lateral / Posterolateral
The common peroneal nerve wraps around the fibular neck and must be identified for posterolateral work or when severe valgus correction places it at stretch risk.
Skin bridge rule
Multiple incisions around the knee can threaten skin vascularity. Plan previous scars, future flaps and fixation incisions before committing to a new approach.
Internervous Plane and Intervals
Some knee approaches use true or practical intervals; others are controlled arthrotomies or tendon-splitting approaches. The safe principle is to name what is being protected and what is being released.
Intervals and Deep Planes
| Approach | Plane or Release | Main Use | Main Risk |
|---|---|---|---|
| Medial parapatellar | Quadriceps tendon and medial retinacular arthrotomy around patella | Primary and revision TKA, joint access | Patellar tendon avulsion, patellar blood supply, arthrotomy closure failure. |
| Midvastus | Split vastus medialis obliquus fibres then medial arthrotomy | Selected primary TKA | Limited exposure, VMO injury or extension into quadriceps tendon. |
| Subvastus | Lift vastus medialis from intermuscular septum without quadriceps tendon split | Selected primary TKA with mobile patella | Difficult exposure in obese, muscular, stiff or revision knees. |
| Posteromedial | Between medial gastrocnemius and pes/hamstring region depending target | Posteromedial tibial plateau and posterior medial corner | Saphenous nerve and vein, posterior capsule, popliteal structures if too deep. |
| Posterolateral | Between biceps femoris, lateral gastrocnemius, fibular head and PLC structures | PLC reconstruction and posterolateral plateau | Common peroneal nerve. |
Posterior knee exposure rule
If the approach moves behind the collateral ligament plane, ask where the popliteal vessels and named nerves are before retracting.
Patient Positioning
Position should give access, imaging, reduction control and bailout options. It is not an afterthought.
Positioning Choices
| Position | Best For | Practical Checks |
|---|---|---|
| Supine | TKA, anterior knee, anterolateral plateau, many medial approaches | Bump, leg holder, tourniquet, foot free, fluoroscopy if fracture fixation. |
| Supine with leg externally rotated or figure-of-four | Posteromedial tibial plateau in selected cases | Access to posterior medial tibia while preserving imaging and anterior access. |
| Lateral | Selected posterolateral or lateral plateau work | Pad peroneal nerve, protect dependent limb, confirm C-arm access. |
| Prone | Direct posterior or selected posterolateral reconstructions | Airway, pressure areas, vascular access and fluoroscopy must be planned. |
Fluoroscopy before draping
For fracture work, confirm AP and lateral imaging before prepping. A perfect approach with unusable fluoroscopy still fails the operation.
Surgical Technique
Use: primary TKA, many revision TKAs, infection washout, extensile anterior joint access.
- Supine position, tourniquet if used, knee free to flex.
- Midline skin incision, respecting prior scars.
- Develop full-thickness flaps only as much as needed.
- Make medial parapatellar arthrotomy through quadriceps tendon, medial retinaculum and around patella.
- Protect patellar tendon insertion at the tibial tubercle.
- Evert or sublux patella according to exposure and extensor tension.
- Release medial sleeve only as needed for deformity correction or exposure.
- Close arthrotomy securely with knee flexion check.
Pitfalls: high arthrotomy extension into quadriceps, patellar tendon avulsion, excessive medial stripping, patellar devascularisation and weak closure.
Structures at Risk and Complications
Approach-Specific Risks
| Structure | At Risk In | Avoidance |
|---|---|---|
| Patellar tendon | Medial/lateral parapatellar, difficult TKA exposure | Avoid forceful eversion; protect tubercle insertion; extend approach rather than avulse tendon. |
| Patellar blood supply | Extensive medial/lateral releases and revision surgery | Limit unnecessary retinacular stripping; preserve soft-tissue attachments. |
| Saphenous nerve / vein | Medial and posteromedial approaches | Identify, mobilise and protect; avoid blind medial dissection. |
| Common peroneal nerve | Posterolateral exposure and severe valgus correction | Identify around fibular neck; avoid traction; document baseline and postoperative function. |
| Skin envelope | Multiple incisions, trauma, revision and infection | Respect skin bridges, prior scars and flap options. |
| Popliteal vessels | Posterior capsule and posterior tibial plateau work | Know depth, use controlled retraction and avoid blind posterior penetration. |
When to extend exposure
Extend when the target cannot be safely reached, the patella cannot be mobilised, reduction cannot be judged, or implant removal requires more access. Controlled extension is safer than force.
When to stop
Stop and reassess when the skin is threatened, the nerve is not identified, the patellar tendon is under excessive tension, or fluoroscopy cannot show the target.
Evidence Base
Every card below is anchored to a verified primary source. The pattern across knee-approach research is consistent: among the standard anterior arthroplasty exposures, differences are small and short-lived, whereas for trauma the approach must be dictated by fragment geometry on CT, and for the posterolateral corner the operation is governed by nerve anatomy.
Subvastus vs medial parapatellar: meta-analysis
- Nine trials, 940 primary TKAs pooled.
- Subvastus favoured for Knee Society function score at 4 to 6 weeks (WMD 5.09) and fewer lateral retinacular releases (OR 0.34).
- No difference in range of motion, operative time, blood loss, length of stay or complications.
Mini-midvastus vs mini-medial parapatellar RCT
- 40 patients with staged bilateral TKA, each patient acting as their own control (one approach per knee).
- Inconsistent clinical differences across timepoints to two years; no difference in operative time, blood loss or lateral releases.
- Authors recommend using the approach the surgeon knows best.
Tibial tubercle osteotomy for difficult exposure
- TTO is reproducible for enhancing exposure in difficult primary and revision TKA.
- Most common complications: proximal migration, osteotomy-site pain and tubercle avulsion.
- Serious TTO-related complications reported in roughly 8 to 9% of cases.
Controversies and Areas of Uncertainty
Knee approaches generate persistent debate where the evidence is short-term, surgeon-dependent or based on small series.
Where Surgeons Disagree
| Question | One View | Other View | Current Position |
|---|---|---|---|
| Subvastus / midvastus vs medial parapatellar for primary TKA | Muscle-sparing approaches speed early extensor recovery and reduce lateral releases. | Differences vanish by 3 to 6 months and exposure is harder in difficult knees. | Reasonable in mobile, non-obese, non-revision knees; long-term outcomes are equivalent (PMID 23218628, 23790343). |
| Patellar eversion vs subluxation | Eversion gives maximal exposure. | Eversion may stress the patellar tendon and extensor mechanism. | Sublux where possible; never force eversion in a stiff knee. |
| Single anterolateral vs combined posterior approach for plateau fractures | Anterolateral plate alone is less invasive. | Posterior coronal fragments lose reduction without a posterior buttress. | CT fragment mapping decides; coronal posterior fragments need a posterior approach (PMID 20881634, 27178768). |
| Tibial tubercle osteotomy vs quadriceps snip / V-Y turndown | TTO gives excellent distal exposure and addresses patella baja. | TTO adds an osteotomy to heal with 8 to 9% serious complications. | Snip first for proximal needs; reserve TTO for greater distal exposure or component removal (PMID 21329253). |
| Posterolateral plateau: direct posterolateral vs extended anterolateral | Direct posterolateral reaches the fragment but risks the peroneal nerve. | Extended anterolateral avoids the nerve but may not control posterior depression. | Match exposure to fragment; identify the common peroneal nerve whenever working posterolaterally. |
Guidelines, Registries and Global Practice
Surgical approaches around the knee are not country-specific, but the evidence and emphasis differ between major societies and between high- and limited-resource settings.
Side-by-Side Guidance
| Body | Emphasis | Practical Takeaway |
|---|---|---|
| AO Foundation | Column- and fragment-based approach selection for the proximal tibia. | Map columns on CT; a posterior column fragment drives a posterior approach and buttress. |
| BOA / BOAST (UK) | Soft-tissue-led timing and combined orthoplastic planning in open and high-energy injuries. | Plan incisions around future flaps; do not commit to an approach that compromises later coverage. |
| AAOS (US) | Implant position, balancing and rehabilitation outweigh small approach differences in TKA. | Choose the arthroplasty exposure you execute safely; optimise alignment and balance. |
| EFORT / European consensus | Anatomy-first exposure with nerve identification for posterolateral and complex knees. | Identify the common peroneal nerve before posterolateral deep work. |
Registry signal
Arthroplasty registries (NJR UK, AJRR US, AOANJRR Australia, the Swedish and Norwegian registers) track implant survival and revision rather than approach. Their consistent message is that component position and balance, not the specific anterior arthrotomy, dominate revision risk.
Global epidemiology
Knee osteoarthritis affects hundreds of millions worldwide and TKA volumes are rising fastest in ageing and middle-income populations. Tibial plateau fractures cluster bimodally: high-energy injuries in younger patients and fragility fractures in older adults.
High-resource setting
Routine preoperative CT with 3D reconstruction, intraoperative fluoroscopy, navigation or robotics for arthroplasty, and ready access to ortho-plastic teams for soft-tissue cover.
Limited-resource setting
Approach planning may rely on plain radiographs, so a disciplined clinical and radiographic read of fragment geometry, deliberate nerve identification and respect for the soft-tissue envelope become even more important.
Viva Scenarios
Use these scenarios to practise clinical reasoning and management decisions
Stiff revision TKA exposure
"A patient requires revision TKA. The knee is stiff, the patella is difficult to mobilise and the previous incision is midline."
Posteromedial plateau fragment
"CT shows a coronal split posteromedial tibial plateau fragment with posterior displacement."
Posterolateral corner exposure
"A young patient has a grade III posterolateral corner injury with a fibular collateral ligament avulsion requiring reconstruction. How do you approach the posterolateral knee safely?"
Knee Surgical Approaches: Decision Sheet
Clinical summary
Opening structure
- •State target pathology first.
- •Then state position, landmarks, interval, danger structures and closure.
- •Do not describe only the skin incision.
Anterior knee
- •Medial parapatellar is reliable and extensile.
- •Subvastus and midvastus are selected primary TKA options.
- •Protect patellar tendon insertion and patellar blood supply.
Posteromedial
- •Used for posteromedial tibial plateau and posterior medial corner access.
- •Protect saphenous nerve and vein.
- •Buttress posterior shear directly.
Posterolateral
- •Used for PLC reconstruction and selected posterolateral plateau work.
- •Identify common peroneal nerve around fibular neck.
- •Avoid blind release or aggressive traction.
Failure modes
- •Wrong approach for target.
- •Patellar tendon avulsion.
- •Skin bridge compromise.
- •Saphenous or peroneal nerve injury.
- •Poor closure of released structures.