Medial or lateral parapatellar approach | Systematic gap-driven lateral release | Balance before resection
- Valgus means LATERAL structures contracted (ITB, LCL, popliteus, posterolateral capsule) while the MEDIAL side (MCL) may be attenuated — the opposite of the varus knee.
- The Krackow classification is ANATOMIC, not degree-based: Type I = MCL intact; Type II = MCL attenuated/incompetent; Type III = valgus after an overcorrected proximal tibial osteotomy. MCL competence, not the angle, drives constraint.
- PROTECT the MCL — in Type II/III it is attenuated and the limiting structure for stability; never release it.
- The release pattern is GAP-driven (Whiteside): tight in extension only → pie-crust the ITB; tight in flexion AND extension → release LCL and popliteus from the femur.
- The common peroneal nerve is at HIGH RISK with lateral releases — overall palsy about 2 percent, higher with valgus and long tourniquet time. Keep the knee flexed and correct only to neutral.
When & Why
Indication. A painful, deformed knee requiring arthroplasty in which the alignment is in valgus — most often lateral-compartment predominant primary osteoarthritis on an anatomic valgus limb, but also inflammatory arthritis (rheumatoid disease classically produces valgus, often bilateral and severe), post-traumatic deformity (malunion of a lateral tibial plateau or lateral femoral condyle fracture), and valgus overcorrection after a previous lateral closing-wedge proximal tibial osteotomy. The shared problem is a contracted lateral soft-tissue sleeve with bone loss laterally and, sometimes, an attenuated medial collateral ligament. The defining decision is soft-tissue, not bony. What makes a valgus knee hard is not the bone cuts but balancing the lateral side without over-releasing it and without injuring the common peroneal nerve. Before committing, work out the Krackow type (see Background & Evidence for the full table): assess the MEDIAL side under stress — an intact MCL is Type I, an attenuated/incompetent MCL is Type II, and post-osteotomy joint-line obliquity is Type III. The type tells you how much lateral release you will need and whether to have a constrained implant in the room.
Familiar to every surgeon and adequate for most Type I and II knees. May need forceful lateral retraction and risks the already-attenuated medial soft tissues in valgus.
Gives direct access to the contracted lateral structures — the release is built into the approach. Favoured for severe fixed valgus and an attenuated MCL because it spares the medial side. The lateral retinaculum is lengthened (coronal Z-plasty or fat-pad flap) for patellar eversion; a tibial tubercle osteotomy is added for difficult exposure. Closure is demanding and the approach is less familiar.
Minimises extensor-mechanism disruption but exposure is difficult in severe valgus; not recommended for significant deformity.
Contraindications are the usual arthroplasty ones: active infection, severe extensor-mechanism dysfunction, a neuropathic joint (relative), and severe vascular insufficiency. Consent specifically for the higher constraint that severe valgus may require, the risk of common peroneal nerve palsy (foot drop), residual instability or overcorrection, and stiffness — and warn the patient preoperatively that a more constrained implant may be chosen on the table. Setup. Supine on a standard table with the knee flexed over a bolster or leg holder, thigh tourniquet, and full flexion and extension confirmed before draping. Standing long-leg alignment films and templating (assessing lateral bone loss) are essential, and constrained components (CCK, rotating-hinge) should be physically in the room, not just on order. Special instrumentation includes a pie-crusting needle (18 G or similar), laminar spreaders for gap assessment, and the constrained implant options.
The Operation
The goal: restore a neutral mechanical axis with symmetric, rectangular flexion and extension gaps by resecting bone correctly and then lengthening the contracted lateral soft-tissue sleeve in a controlled, gap-driven sequence — all while protecting the attenuated MCL and the common peroneal nerve. The exposure is laid out in full as the opening steps below (and in depth on the medial parapatellar and lateral parapatellar approach pages).
Operative sequence
- Supine, leg holder or bolster, thigh tourniquet; confirm full flexion and extension.
- Standing long-leg films and templating in hand — assess lateral condyle/plateau bone loss.
- Constrained implants (CCK, rotating-hinge) physically in the room.
- Choose approach now: medial parapatellar for most; lateral (Keblish) for severe fixed valgus or an attenuated MCL.
- Medial parapatellar: standard midline incision, medial arthrotomy, sublux or evert the patella. Adequate for Type I/II; watch for forceful lateral retraction.
- Lateral parapatellar (Keblish): direct access to the contracted lateral structures — the release is essentially built into the approach and the medial tissues are spared. Lengthen the lateral retinaculum (coronal Z-plasty or fat-pad flap) for eversion; add a tibial tubercle osteotomy for a tight extensor mechanism.
- Sublux or evert the patella and expose both compartments.
- Document fixed versus correctable deformity; apply gentle varus stress to test passive correction.
- Assess the MEDIAL side under stress and assign the Krackow type (Type I MCL intact; Type II MCL attenuated/incompetent; Type III post-osteotomy joint-line obliquity).
- If passively correctable toward neutral, expect a Type I/II pattern; a fixed deformity signals more lateral work.
- Perform the tibial cut FIRST in valgus knees — it allows better assessment of the deformity.
- Extramedullary guide, cut perpendicular to the mechanical axis (0 degrees varus/valgus), referencing off the lateral (higher) plateau.
- Preserve bone stock; avoid excessive resection. The medial plateau sits LOWER — do not under-resect medially.
- Intramedullary guide with the valgus correction angle set appropriately.
- In the valgus knee less anatomic valgus correction is usually needed (3 to 5 degrees rather than the standard 5 to 7 degrees) because anatomic valgus is already present.
- Setting the standard 5 to 7 degrees risks under-resecting laterally and over-resecting the medial condyle.
- Check the extension gap with a laminar spreader.
- With trials in place, assess the extension gap; in the valgus knee expect LATERAL tightness.
- Document the asymmetry in millimetres (medial versus lateral). A useful rule of thumb: each 1 mm of lateral release adds about 1 degree of correction.
- Plan the release from the gap pattern, not from a fixed sequence.
- Make multiple percutaneous inside-out stab punctures through the iliotibial band at the level of the joint line, using an 18 G needle or number 11 blade.
- Space the stabs about 5 mm apart; each puncture lengthens the ITB by 2 to 3 mm.
- Reassess balance after each set — pie-crusting is safe, controlled lengthening that adds up.
- The stabs stay proximal to the fibular head, keeping the CPN safe.
- If ITB pie-crusting is insufficient, release the posterolateral capsule (arcuate complex) off the lateral tibial plateau with electrocautery, staying on bone — mainly for persistent extension tightness.
- Release the popliteus tendon from its FEMORAL origin; this preserves the tibial attachment for some residual constraint and opens a tight lateral flexion gap.
- Match the release to the gap (Whiteside): tight in extension ONLY → ITB; tight in BOTH flexion and extension → LCL and popliteus released from the femur, where they can be recessed in a controlled, subperiosteal way and re-tension at the correct length.
- If still unbalanced, release the LCL from the lateral femoral epicondyle by subperiosteal elevation with cautery, preserving the fibular attachment — a significant release that may create lateral laxity.
- Lateral epicondylar osteotomy is the LAST RESORT: osteotomise the entire lateral epicondyle with LCL and popliteus attached and let it slide distally (fix or accept malunion). Needing it signals severe deformity and a strong indication for a CCK.
- Overall release order: ITB → posterolateral capsule → popliteus → LCL → epicondylar osteotomy.
- Size the femoral component and set rotation using the transepicondylar axis — the most reliable reference in valgus.
- The posterior condylar axis is UNRELIABLE in valgus because the lateral femoral condyle (especially posteriorly) is hypoplastic; using it drives internal rotation and patellar maltracking.
- Make the anterior, posterior and chamfer cuts.
- Re-check flexion and extension gaps; the goal is symmetric rectangular gaps.
- Choose constraint by the balance achieved, not by the angle. If residual lateral laxity is greater than 10 degrees, use a CCK; if there is bilateral collateral incompetence, consider a rotating hinge.
- Accept neutral to 2 to 3 degrees of residual valgus rather than overcorrect into varus — varus overcorrection causes rapid medial wear.
- Cement the components with standard technique.
- Final check of balance, range of motion and patellar tracking (no-thumb test).
- If a lateral approach was used, repair/lengthen the lateral retinaculum; layered closure.
- Consider a hinged brace if stability is borderline.
The common peroneal nerve curves around the fibular neck, only 2 to 3 cm from the lateral joint line, and is at high risk with any lateral release or forced lateral retraction. Protect it throughout: keep the knee flexed during lateral work (this moves the nerve and the popliteal bundle posteriorly and relaxes the nerve), avoid aggressive posterior-lateral retraction, and limit the total correction toward neutral rather than into varus. If foot drop appears postoperatively, loosen all dressings and flex the knee to 30 to 40 degrees immediately to take tension off the nerve.
The popliteal artery and vein lie directly behind the posterior capsule, closest to bone in extension and at the level of the joint line. They move slightly posteriorly with knee flexion. For any posterior capsular release keep the knee flexed and stay strictly subperiosteal — never plunge a saw blade, osteotome or deep posterior retractor through the posterior capsule.
In Type II/III valgus the medial collateral ligament is attenuated and is the limiting structure for stability. Do not release it, and avoid forceful medial retraction or aggressive manipulation that could rupture it. If the MCL is incompetent, escalate constraint (CCK, or a rotating hinge for global incompetence) rather than accept medial laxity.
The lateral release is gap-driven, not a fixed ladder. Tight in extension only → the ITB is the offender, so pie-crust it. Tight in both flexion and extension → the LCL and popliteus are responsible, so release them from the femur, which lengthens them in a controlled, subperiosteal way and lets them re-tension at the correct length. The posterolateral capsule is released only for persistent extension tightness. Reassess after each step.
Accept neutral to 2 to 3 degrees of residual valgus. Overcorrecting a valgus knee into varus loads the medial compartment and causes rapid medial wear and poor outcomes. Reduce the distal femoral valgus cut angle (3 to 5 degrees rather than 5 to 7 degrees) and resist the urge to tension the lateral side by over-releasing.
In valgus the posterior condylar axis is unreliable because of lateral condyle hypoplasia. Set femoral rotation from the transepicondylar axis. Using the posterior condylar axis drives internal rotation, anteriorises the trochlear groove and causes patellar maltracking.
Aftercare & Complications
Rehabilitation. Weight-bearing as tolerated is the default, with a hinged brace for 6 weeks whenever there is any concern about stability. Standard VTE prophylaxis is used throughout. Physiotherapy concentrates on quadriceps activation and range of motion, with early mobilisation and adequate analgesia to avoid stiffness. Most patients progress to independent mobility over the first 6 weeks. Complications
- Recognition
- Foot drop with sensory loss over the lateral leg and dorsum of the foot postoperatively
- Prevention
- Keep the knee flexed for lateral work, avoid aggressive retraction, limit correction to neutral
- Management
- Loosen dressings and flex the knee to 30 to 40 degrees immediately; observe 12 to 18 months (most are neurapraxia); AFO for foot drop; explore if no recovery
- Recognition
- Lateral gapping on stress, a feeling of giving way, recurrent valgus
- Prevention
- Systematic lateral release; adequate constraint (CCK if laxity greater than 10 degrees)
- Management
- Bracing first; revision to higher constraint if symptomatic
- Recognition
- New medial laxity, varus instability, pain
- Prevention
- Protect the attenuated MCL — no medial retraction or aggressive manipulation
- Management
- CCK or rotating hinge if severe; brace if minimal
- Recognition
- Postoperative varus alignment, medial pain, medial compartment wear
- Prevention
- Accept 2 to 3 degrees residual valgus; reduce the valgus cut angle; careful release
- Management
- Revision if symptomatic with medial overload
- Recognition
- Anterior knee pain, lateral tilt, catching or clunking
- Prevention
- Set rotation from the transepicondylar axis; avoid internal rotation
- Management
- Lateral retinacular release; revision if the component is malrotated
- Recognition
- Flexion under 90 degrees at 6 weeks, difficulty with stairs
- Prevention
- Careful balancing, early mobilisation, adequate analgesia
- Management
- Manipulation under anaesthesia before 12 weeks; arthroscopic lysis of adhesions if late
Viva & Exam Focus
LATERALLATERAL — the valgus lateral release sequence
TYPETYPE — Krackow classification is anatomic
Around the fibular neck, 2 to 3 cm from the lateral joint line. At HIGH RISK with lateral releases and retraction. Protect it with a flexed knee and gentle retraction; limit correction to neutral.
Directly behind the posterior capsule, closest to bone in extension and at the joint line; it moves posteriorly with flexion. Stay subperiosteal with the knee flexed for any posterior release; never plunge instruments through the capsule.
From the medial femoral epicondyle to the proximal tibia. Attenuated in the valgus knee and the limiting structure for stability — protect it, never release it, avoid medial retraction.
From the lateral femoral epicondyle to the fibular head. Release from the femur if needed, preserving the fibular attachment for some residual constraint.
Courses around the lateral femoral condyle and may be injured during lateral release. Have diathermy ready for haemostasis.
Clinical Decision Scenarios
Practise clinical reasoning and management decisions out loud
“You are performing a TKA on a 65-year-old woman with rheumatoid arthritis and a fixed 20 degree valgus deformity. After the bone cuts the lateral extension gap is 15 mm and the medial is 22 mm. Describe your approach to balancing.”
“A patient develops a foot drop on postoperative day 1 after TKA for severe valgus deformity. How do you assess and manage this?”
“During TKA for Type III valgus you perform extensive lateral releases but there remains 15 degrees of lateral laxity in extension. What is your management?”
Key Pathology
- Valgus = LATERAL contracted, MEDIAL attenuated
- Tight: ITB, LCL, popliteus, posterolateral capsule
- Stretched and fragile: the MCL — protect it throughout
- Lateral femoral condyle often hypoplastic (posteriorly)
Krackow Classification (anatomic)
- Type I: lateral contracture, MCL intact — lateral release, low constraint
- Type II: MCL attenuated or incompetent — lateral release, often a CCK
- Type III: post-osteotomy tibial joint-line obliquity — correct geometry, constraint as needed
- Based on MEDIAL competence, not the degree of valgus (exam trap)
Lateral Release Sequence
- 1. ITB pie-crusting at the joint line (safest, controlled)
- 2. Posterolateral capsule (arcuate complex)
- 3. Popliteus from the femoral origin
- 4. LCL from the lateral femoral epicondyle
- 5. LAST: lateral epicondylar osteotomy (rare)
Constraint Selection
- CR: competent MCL, balanced, PCL intact
- PS: competent MCL, balanced, PCL deficient or released
- CCK: residual coronal laxity or MCL attenuation after full release
- RHK: global or bilateral collateral incompetence, major bone loss
Critical Exam Points
- Protect the CPN — flex the knee, gentle retraction
- Protect the MCL — attenuated, never release it
- Accept 2 to 3 degrees residual valgus (better than varus overcorrection)
- Transepicondylar axis for rotation (posterior condylar unreliable)
Key Complications
- CPN palsy — most recover (neurapraxia); AFO needed
- Residual instability — consider revision to a CCK
- Overcorrection to varus — causes rapid medial wear
- Patellar maltracking — from internal rotation
Background & Evidence
Pathoanatomy. The valgus knee combines lateral bone deficiency (lateral femoral condyle and lateral tibial plateau) with lateral capsuloligamentous contracture — the iliotibial band (tight mainly in extension), the lateral collateral ligament and popliteus (tight in flexion and extension) and the posterolateral capsule. The lateral femoral condyle is often hypoplastic posteriorly, which makes the posterior condylar axis unreliable for rotation. The patella is frequently laterally subluxed and maltracking. The medial collateral ligament is competent in Type I but attenuated or incompetent in Type II. A separate, purely descriptive severity grading by deformity magnitude (mild under 15 degrees, moderate 15 to 30 degrees, severe over 30 degrees) is widely quoted but should not be confused with the Krackow types.
- Defining feature
- Valgus from lateral bone loss and lateral soft-tissue contracture
- MCL status
- Intact
- Typical management
- Lateral soft-tissue release; CR or PS, low constraint
- Defining feature
- Obvious attenuation or insufficiency of the medial capsuloligamentous complex
- MCL status
- Incompetent
- Typical management
- Lateral release and manage medial laxity; many surgeons use a CCK
- Defining feature
- Valgus malalignment of the proximal tibial joint line after an overcorrected proximal tibial osteotomy
- MCL status
- Variable
- Typical management
- Correct tibial joint-line obliquity plus release; constraint as dictated by stability
References
Primary total knee arthroplasty in patients with fixed valgus deformity
- 99 valgus knees (versus 40 non-deformed controls) followed 2 to 10 years; defined the classification still used today
- Type I = lateral contracture with intact medial structures; Type II = attenuated medial capsuloligamentous complex; Type III = post-osteotomy joint-line obliquity
- Type I treated with lateral release alone, Type II historically with medial tightening; mean postoperative Knee Society score 87.6
- The classification is anatomic (medial competence), NOT based on the degree of valgus
Selective ligament release in total knee arthroplasty of the knee in valgus
- 231 valgus knees (12 to 45 degrees) balanced by gap-pattern-specific release rather than a fixed sequence
- Knees tight in BOTH flexion and extension: release LCL and popliteus from the femur
- Knees tight in extension ONLY: release the iliotibial band; posterior capsule released only for persistent tightness
- All knees fell within 4 to 7 degrees mean laxity; no ligament advancement or constrained implant was needed and stability did not deteriorate over time
10- to 20-year followup of total knee arthroplasty for valgus deformities
- 108 valgus knees (over 10 degrees valgus); 60 knees followed a mean 14.1 years
- Lateral release of retinaculum and ITB, then detachment of LCL and popliteus from the femur when needed
- Mean postoperative alignment 4.5 degrees valgus with 75 percent corrected to 2 to 7 degrees; prosthesis survival 91 percent at 13.2 years
- Postoperative instability occurred in 24 percent of all knees, prompting a revised soft-tissue technique
Does postoperative epidural analgesia increase the risk of peroneal nerve palsy after total knee arthroplasty?
- 361 TKAs; overall peroneal nerve palsy incidence 2.2 percent
- Significant risk factors: preoperative valgus deformity 10 degrees or greater, tourniquet time over 120 minutes, pre-existing neuropathy and postoperative bleeding
- Epidural analgesia did not raise risk but delayed diagnosis — all motor palsies presented after the epidural was stopped
- High-risk patients should be monitored closely with dilute local anaesthetic or opioid-only infusions
Total knee arthroplasty in the valgus knee
- Authoritative review of valgus-knee pathoanatomy and surgical strategy
- Combined bone deficiency (lateral condyle and plateau) with lateral capsuloligamentous contracture, sometimes with MCL laxity
- Understanding the specific pathologic anatomy is the prerequisite to component positioning and soft-tissue balance
- Covers approach choice, release options and constraint escalation
Further reading. 1. Krackow KA, Jones MM, Teeny SM, Hungerford DS. Primary total knee arthroplasty in patients with fixed valgus deformity. Clin Orthop Relat Res. 1991;(273):9-18. PMID 1959292. (Original classification) 2. Whiteside LA. Selective ligament release in total knee arthroplasty of the knee in valgus. Clin Orthop Relat Res. 1999;(367):130-140. PMID 10546607. 3. Miyasaka KC, Ranawat CS, Mullaji A. 10- to 20-year followup of total knee arthroplasty for valgus deformities. Clin Orthop Relat Res. 1997;(345):29-37. PMID 9418618. 4. Favorito PJ, Mihalko WM, Krackow KA. Total knee arthroplasty in the valgus knee. J Am Acad Orthop Surg. 2002;10(1):16-24. PMID 11809047. DOI 10.5435/00124635-200201000-00004. 5. Horlocker TT, Cabanela ME, Wedel DJ. Does postoperative epidural analgesia increase the risk of peroneal nerve palsy after total knee arthroplasty? Anesth Analg. 1994;79(3):495-500. PMID 8067554. DOI 10.1213/00000539-199409000-00016. 6. Bellemans J. Multiple needle puncturing: balancing the varus knee. Orthopedics. 2011;34(9):e510-2. PMID 21902147. DOI 10.3928/01477447-20110714-48. (Pie-crusting and controlled ligament lengthening technique) 7. Zhou X, Wang M, Liu C, Zhang L, Zhou Y. Total knee arthroplasty for severe valgus knee deformity. Chin Med J (Engl). 2014;127(6):1062-6. PMID 24622435. 8. National Joint Registry (NJR) for England, Wales, Northern Ireland and the Isle of Man; American Joint Replacement Registry (AJRR); Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR); Swedish and Norwegian Arthroplasty Registers — annual reports (implant survivorship and constraint-related revision data).