Advanced Bilateral Knee Osteoarthritis: A Comprehensive Clinical Case Study

Patient Presentation & History

A 68-year-old male, a retired carpenter, presented to the Orthopedic Clinic with a chief complaint of progressively worsening bilateral knee pain, significantly more pronounced in the right knee, over the past seven years. The pain is described as a deep, aching sensation, exacerbated by weight-bearing activities, prolonged standing, climbing stairs, and rising from a seated position. He reports significant morning stiffness lasting approximately 45 minutes and stiffness after periods of inactivity. He rates his pain as 7/10 on a visual analog scale (VAS) at its worst, interfering with his ability to perform daily activities, including walking for more than two blocks and standing for over 15 minutes. He requires a cane for ambulation due to pain and instability.

He denies any specific mechanism of acute injury to either knee. His pain began insidiously and has progressively worsened despite various conservative interventions. He previously underwent a diagnostic arthroscopy and partial medial meniscectomy on the right knee approximately ten years prior, which provided temporary relief for about 18 months. Over the last three years, he has tried extensive physical therapy, oral NSAIDs (diclofenac 75mg BID with omeprazole), corticosteroid injections (three times in the past year, with diminishing returns), and hyaluronic acid injections (a single series six months ago with no significant benefit).

Past Medical History:
* Hypertension, well-controlled with lisinopril 10mg daily.
* Type 2 Diabetes Mellitus, well-controlled with metformin 1000mg BID, HbA1c 6.7%.
* Obesity (BMI 32 kg/m²).
* Hyperlipidemia, controlled with atorvastatin 20mg daily.
* No history of DVT/PE or bleeding disorders.

Past Surgical History:
* Right knee diagnostic arthroscopy with partial medial meniscectomy (10 years prior).
* Appendectomy (childhood).

Social History:
* Former smoker (quit 15 years ago, 20 pack-year history).
* Occasional alcohol consumption.
* Lives with his wife in a single-story home. Highly motivated for surgical intervention to improve his quality of life and maintain independence.

Medications: Lisinopril, Metformin, Atorvastatin, Omeprazole, Diclofenac (as needed).
Allergies: Penicillin (rash).

Clinical Examination

General Appearance:
The patient is an elderly male, appearing his stated age, in no acute distress at rest, but with an antalgic gait noted during ambulation into the examination room, favoring his right lower extremity.

Inspection:
* Right Knee: Visible varus deformity. Mild quadriceps atrophy compared to the left. No overt swelling or erythema. Previous anteromedial arthroscopy scars are well-healed. No signs of skin compromise or trophic changes.
* Left Knee: Mild varus alignment. No significant swelling or erythema. Mild quadriceps atrophy.

Palpation:
* Right Knee: Significant tenderness along the medial joint line and medial femoral condyle. Mild tenderness over the patellofemoral joint. No significant warmth or palpable effusion. No palpable Baker's cyst.
* Left Knee: Mild tenderness along the medial joint line. No significant warmth or effusion.

Range of Motion (Active and Passive):
* Right Knee:
* Flexion: 0° to 95° (active and passive).
* Extension: Fixed flexion deformity of 10°.
* Crepitus: Marked, coarse crepitus throughout the arc of motion, particularly with patellofemoral translation.
* Left Knee:
* Flexion: 0° to 110° (active and passive).
* Extension: Full (0°).
* Crepitus: Moderate, fine crepitus.

Ligamentous Stability (Right Knee):
* Varus Stress Test: Minimal laxity at 0° extension; significant laxity (>10mm opening) at 30° flexion, indicating severe medial collateral ligament (MCL) attenuation/insufficiency.
* Valgus Stress Test: Stable at 0° and 30° flexion.
* Anterior/Posterior Drawer: Minimal sag. ACL/PCL appear functionally intact, but assessment is limited by pain and deformity.
* Lachman Test: Not performed due to advanced OA.
* Patellar Mobility: Reduced lateral glide, mild patellar tilt. Significant patellofemoral crepitus.

Neurological Assessment (Bilateral Lower Extremities):
* Motor Strength: 5/5 in all major muscle groups (quadriceps, hamstrings, tibialis anterior, gastrocnemius, extensor hallucis longus) bilaterally, with subjective weakness during painful maneuvers of the right knee.
* Sensation: Intact to light touch in all dermatomes (L2-S1) bilaterally.
* Reflexes: 2+ and symmetrical at patella and Achilles bilaterally.

Vascular Assessment (Bilateral Lower Extremities):
* Dorsalis pedis and posterior tibial pulses are 2+ and symmetrical bilaterally. Capillary refill <2 seconds. No signs of venous stasis.

Imaging & Diagnostics

Plain Radiographs (Right Knee):
* Standing Anteroposterior (AP) View:
* Severe, near-complete loss of joint space in the medial compartment (medial tibiofemoral JSN).
* Significant subchondral sclerosis and cyst formation in both the medial femoral condyle and medial tibial plateau.
* Large, well-defined osteophytes present on the medial aspects of the femoral condyle and tibial plateau.
* Severe varus deformity, with the mechanical axis falling significantly medial to the center of the knee.
* Kellgren-Lawrence (KL) Grade IV osteoarthritis.
* Lateral View:
* Posterior tibial slope appears within normal limits.
* Evidence of distal femoral osteophytes and posterior tibial plateau osteophytes.
* Patellar height within normal limits (Insall-Salvati ratio ~1.0).
* Fixed flexion deformity of approximately 10 degrees confirmed.
* Merchant (Axial Patellar) View:
* Severe patellofemoral joint space narrowing, particularly laterally.
* Subchondral sclerosis and osteophyte formation at the patellofemoral articulation.
* Patellar tilt and mild lateral subluxation.
* Full-Length Bilateral Lower Extremity Mechanical Axis View:
* Confirms a significant right lower extremity varus alignment (mechanical axis deviation approximately 25mm medial to the center of the knee).
* Contributes to a calculated tibiofemoral angle of 15° varus.
* Left knee demonstrates mild varus alignment (mechanical axis deviation 5mm medial).

Computed Tomography (CT) Scan (Right Knee):
* A CT scan was obtained for precise bone morphology assessment and to plan for potential bone loss management, given the severity of the varus deformity and chronic MCL insufficiency.
* Findings: Confirmed severe tricompartmental osteoarthritis with extensive medial tibiofemoral and patellofemoral degeneration. No significant bone defects requiring augments were noted on the tibial plateau or femoral condyle beyond what could be managed with standard resections and potentially bone grafting if required after definitive cuts. Precise quantification of the rotational profile of the distal femur and proximal tibia was obtained, indicating no significant torsional deformities.

Magnetic Resonance Imaging (MRI) (Right Knee):
* Not indicated in this case due to clear radiographic evidence of end-stage osteoarthritis and the decision for total knee arthroplasty (TKA). MRI is typically more useful for early-stage OA, meniscal tears, ligamentous injuries, or osteonecrosis when the diagnosis is less clear or when considering arthroscopy as a joint-preserving option.

Pre-operative Templating:
* Utilizing the standing AP and full-length mechanical axis views, templating was performed.
* Anticipated femoral component size: Approximately 70-75mm (posterior condylar width).
* Anticipated tibial component size: Approximately 75-80mm (AP width).
* Planned distal femoral cut: 5° to 6° valgus angle relative to the femoral anatomical axis, to restore the mechanical axis.
* Planned proximal tibial cut: Perpendicular to the mechanical axis (0° varus/valgus), with a 5° posterior slope.
* Pre-operative planning indicated that a standard posterior-stabilized (PS) TKA system would be appropriate, with potential need for medial collateral ligament release and careful balancing.

Differential Diagnosis

The patient's clinical presentation and radiographic findings are highly consistent with end-stage tricompartmental osteoarthritis of the right knee. However, for a comprehensive approach, other conditions that can cause similar knee pain or lead to knee reconstruction should be considered.

Surgical Decision Making & Classification

The decision for surgical intervention, specifically Total Knee Arthroplasty (TKA), was made based on several key factors:

1. Failure of Comprehensive Conservative Management: The patient had undergone an extensive course of non-operative treatments including physical therapy, oral NSAIDs, intra-articular corticosteroid and hyaluronic acid injections, and activity modification, all of which provided only temporary or no significant relief. This is a critical prerequisite for considering elective arthroplasty.
2. Severity of Symptoms and Functional Impairment: The patient's pain (VAS 7/10) significantly impacted his quality of life, restricting ambulation, activities of daily living, and leading to dependence on a cane. His fixed flexion deformity and limited range of motion further exacerbated his functional limitations.
3. Radiographic Evidence of End-Stage Disease: The standing radiographs confirmed severe, tricompartmental osteoarthritis (Kellgren-Lawrence Grade IV) with significant joint space narrowing, osteophyte formation, subchondral sclerosis, and a marked varus deformity. This indicates irreversible articular cartilage destruction.
4. Patient Motivation and Expectations: The patient was highly motivated to undergo surgery to improve his mobility and reduce pain, demonstrating a clear understanding of the risks and benefits of TKA.

Classification Systems Relevant to Decision Making:

• Kellgren-Lawrence (KL) Classification: This system, used to grade the severity of osteoarthritis based on plain radiographs, classified the patient's right knee as KL Grade IV , indicating severe OA with large osteophytes, marked joint space narrowing, severe sclerosis, and definite deformity of bone ends. This grade strongly supports surgical intervention.
• Anderson Orthopaedic Research Institute (AORI) Classification: While primarily used for bone defects in revision arthroplasty, the principles of identifying and addressing bone loss are crucial for complex primary TKAs, especially in cases with severe deformity. In this case, pre-operative CT imaging and templating did not indicate AORI Type 1 or Type 2 defects that would necessitate augments or special implants, but the possibility was considered given the severe varus. The varus deformity here was primarily due to soft tissue contracture medially and bone wear, rather than significant bone loss requiring reconstruction.
• Insall-Salvati Index: Used to assess patellar height on a lateral knee radiograph. The patient's index was approximately 1.0, indicating normal patellar height. This information is important for patellar tracking and potential patellar resurfacing decisions.
• Varus Deformity Assessment: The patient exhibited a severe varus deformity with significant medial laxity (opening >10mm at 30° flexion). This dictates the need for systematic soft tissue release of the medial structures (deep MCL, posteromedial capsule, semimembranosus) to achieve a balanced knee in extension and flexion. A fixed flexion deformity of 10° further necessitates careful bone resection and potentially further posterior capsular release.

Given the combination of intractable pain, severe functional limitation, advanced radiographic changes, and failed non-operative management, a primary Total Knee Arthroplasty (TKA) using a posterior-stabilized (PS) implant was deemed the most appropriate surgical intervention for the patient's right knee. A staged TKA for the left knee would be considered in the future based on recovery from the right TKA and persistence of symptoms.

Surgical Technique / Intervention (Right Total Knee Arthroplasty)

Pre-operative Preparation:
* Anesthesia: General anesthesia combined with a femoral nerve block and adductor canal block for multimodal pain management.
* Antibiotic Prophylaxis: Intravenous cefazolin 2g administered 30-60 minutes prior to incision, with re-dosing every 3-4 hours if the case is prolonged. Vancomycin used for penicillin allergy.
* Patient Positioning: Supine on the operating table. A pneumatic tourniquet was applied to the right thigh, followed by sterile preparation and draping of the entire lower extremity from the mid-thigh to the foot. A side support or leg holder was used to stabilize the femur. The foot was positioned in a sterile boot or held by a dedicated assistant for controlled manipulation.

Surgical Approach and Exposure:
* Incision: A standard midline skin incision was made, extending approximately 3cm above the superior pole of the patella to 2-3cm medial to the tibial tubercle, centered over the knee. Dissection was carried down through subcutaneous tissue to the deep fascia.
* Arthrotomy: A medial parapatellar arthrotomy was performed, beginning superiorly in the quadriceps tendon, extending distally along the medial border of the patella, and terminating just medial to the patellar tendon insertion.
* Patellar Eversion: The patella was carefully everted laterally to expose the femoral trochlea and condyles, and the tibial plateau. Care was taken to avoid excessive tension on the patellar tendon.
* Synovectomy/Meniscectomy: Remaining meniscal remnants and hypertrophic synovium were meticulously excised to improve visualization and facilitate bone cuts. Anterior osteophytes were also removed.

Bone Resections and Alignment:
* Distal Femoral Resection:
* An intramedullary (IM) guide was used to determine the valgus cut angle. Given the patient's anatomical axis and typical valgus angles for TKA, a 5° valgus resection was planned to restore mechanical axis alignment.
* The IM rod was inserted into the femoral canal, and the distal femoral cutting block was secured, ensuring 3° of external rotation relative to the posterior condylar axis to prevent patellar maltracking and achieve a balanced flexion gap.
* The distal femur was resected to establish the extension gap. All osteophytes were removed from the posterior femur.
* Proximal Tibial Resection:
* An extramedullary (EM) guide was utilized to ensure the tibial cut was perpendicular to the mechanical axis (0° varus/valgus) and to incorporate a 5° posterior slope for kinematics and preventing anterior impingement.
* The cutting block was positioned, accounting for the desired amount of resection (typically 8-10mm from the least affected side). The proximal tibia was resected.
* Posterior Femoral Condylar Resection:
* A 4-in-1 or 5-in-1 cutting block was applied to the distal femur, referencing the resected distal surface and the posterior condylar axis with 3° external rotation to prepare the anterior, posterior, chamfer cuts and post box (for PS design).
* All remaining peripheral osteophytes were removed from the femoral and tibial cuts to ensure proper seating of components and soft tissue balancing.

Soft Tissue Balancing (Crucial for Varus Deformity):
* This is the most critical step in correcting a varus knee and achieving balanced flexion and extension gaps.
* Extension Gap Balancing:
* With the knee in full extension, tensioning devices were used to assess the medial and lateral gaps. Given the severe varus and medial laxity, the medial compartment was significantly tighter, and the lateral compartment relatively loose.
* A systematic, sequential release of the medial soft tissues was performed:
1. Deep Medial Collateral Ligament (MCL): Releases initiated from the posterior aspect of the MCL, then progressing anteriorly as needed. Care was taken to preserve the superficial MCL if possible.
2. Semimembranosus tendon: Release of its insertion on the posteromedial aspect of the tibia.
3. Posteromedial Capsule: Released as necessary.
* The goal was to achieve a rectangular and symmetrical extension gap, matching the lateral side.
* Flexion Gap Balancing:
* With the knee in 90° flexion, tensioning devices were re-applied.
* Flexion gap imbalances in a varus knee are typically due to tight medial structures or posterior osteophytes. Any remaining medial tightness (after extension gap balancing) would be addressed with further deep MCL or semimembranosus release.
* The goal was to achieve a balanced and rectangular flexion gap, equal to the extension gap, to avoid flexion instability or tightness.

Patellar Resurfacing and Tracking:
* The patella was prepared by excising peripheral osteophytes and making a uniform resection of the articular cartilage surface (typically 8-10mm thickness).
* A patellar component was sized and cemented into place.
* Patellar tracking was assessed with trial components in situ. The "no-thumb" test was performed, ensuring the patella tracked centrally without lateral subluxation or tilt throughout the range of motion. If lateral tracking was observed, a lateral retinacular release would be performed, judiciously, from distal to proximal.

Trial Reduction and Final Implantation:
* Trial femoral, tibial, and patellar components were inserted.
* Full range of motion was assessed, checking for stability, tracking, impingement, and appropriate tension in flexion and extension. The knee should extend fully and flex beyond 110-120 degrees without impingement or instability.
* Once optimal component size and balancing were confirmed, the definitive components were implanted.
* Cementation: Thorough lavage and drying of bone surfaces. Polymethylmethacrylate (PMMA) bone cement was mixed and applied to the bone-implant interfaces, ensuring adequate cement mantle. Components were carefully seated and held under pressure until cement polymerization. Excess cement was removed.
* A polyethylene bearing insert (PS design) was impacted into the tibial tray.

Closure:
* Thorough irrigation of the joint.
* Hemostasis was achieved.
* A drain was not routinely used but may be considered for larger cases or patients on anticoagulants.
* The medial parapatellar arthrotomy was closed in layers with absorbable sutures.
* Subcutaneous layers were approximated, and skin was closed with staples.
* A sterile compressive dressing was applied.

Post-Operative Protocol & Rehabilitation

Immediate Post-Operative Period (Day 0-3 Hospital Stay):
* Pain Management: Multimodal approach including peripheral nerve blocks (femoral/adductor), oral opioids, NSAIDs (if not contraindicated), acetaminophen, and gabapentinoids.
* DVT Prophylaxis: Low molecular weight heparin (LMWH) or aspirin per institutional protocol, initiated immediately post-op and continued for 4-6 weeks. Early mobilization is paramount.
* Wound Care: Dressing changes on post-operative day 2-3. Staples typically removed at 2-3 weeks.
* Mobility: Early mobilization is crucial. Patient encouraged to sit out of bed, perform ankle pumps, and begin weight-bearing as tolerated (WBAT) with an assistive device (walker/crutches) on post-operative day 0 or 1.
* Physical Therapy (PT): Initiated on post-operative day 0 or 1.
* Goals:
* Achieve full knee extension (0°).
* Achieve at least 90° of knee flexion.
* Quadriceps setting exercises, gluteal sets.
* Assisted transfers and gait training with assistive device.
* Continuous Passive Motion (CPM) machine: Often used in the immediate post-operative period, though its routine benefit remains controversial and is institution-dependent.

Phase I: Acute Rehabilitation (Weeks 1-6)
* Goals:
* Reduce pain and swelling.
* Achieve 0-110° (or more) ROM.
* Improve quadriceps activation and strength.
* Restore independent ambulation with an assistive device.
* Safe ascent and descent of stairs.
* Exercises:
* Active and passive ROM exercises.
* Quadriceps strengthening (straight leg raises, vastus medialis obliquus (VMO) isolation).
* Hamstring curls.
* Gluteal strengthening (hip abduction/extension).
* Proprioceptive exercises (weight shifting).
* Gait training, progressing from walker to cane.
* Precautions: Avoid twisting motions. Adhere to weight-bearing status. Watch for signs of infection (fever, redness, warmth, discharge).

Phase II: Intermediate Rehabilitation (Weeks 6-12)
* Goals:
* Achieve 0-120° (or more) ROM.
* Progressive strengthening of lower extremity musculature.
* Improve balance and proprioception.
* Discontinue assistive devices for ambulation.
* Return to light recreational activities.
* Exercises:
* Progressive resistance exercises (ankle weights, resistance bands, stationary bike).
* Functional exercises (mini-squats, lunges, step-ups).
* Balance training (single-leg stance, wobble board).
* Increased walking endurance.
* Precautions: Avoid high-impact activities. Gradually increase intensity and duration of exercises.

Phase III: Advanced Rehabilitation (Weeks 12 onwards)
* Goals:
* Full functional recovery for daily activities.
* Return to pre-surgical recreational activities (within limits for TKA, e.g., no running/jumping).
* Maximize strength, endurance, and flexibility.
* Exercises:
* Advanced strengthening (leg press, hamstring curls, calf raises).
* Agility drills (if appropriate).
* Continued low-impact cardiovascular activities (swimming, cycling, walking).
* Long-Term Follow-up: Regular clinical and radiographic follow-up, typically at 1 year, 2 years, 5 years, and then every 5 years, to monitor implant integrity, alignment, and detect any signs of loosening or wear.

Potential Complications:
* Early Complications: Infection (superficial or deep), DVT/PE, nerve injury (peroneal nerve palsy), vascular injury, wound complications (dehiscence, hematoma), acute stiffness, persistent pain, component malposition.
* Late Complications: Aseptic loosening, polyethylene wear, periprosthetic fracture, instability, chronic stiffness (arthrofibrosis), patellofemoral complications, heterotopic ossification.

Pearls & Pitfalls (Crucial for FRCS/Board Exams)

Pearls for Total Knee Arthroplasty in Osteoarthritis:

1. Thorough Pre-operative Planning:
   • Full-Length Mechanical Axis Radiographs: Absolutely essential. These films allow for accurate assessment of the patient's mechanical axis deviation, identifying whether the deformity is predominantly femoral, tibial, or a combination, and are crucial for templating and planning bone resections to restore neutral alignment.
   • Templating: Use pre-operative radiographs to template for femoral and tibial component sizes and to estimate the valgus cutting angle for the distal femur. This provides a roadmap and helps anticipate potential challenges (e.g., severe deformity, bone loss).
   • Fixed Flexion Deformity (FFD): A significant FFD (e.g., >10°) requires careful management, often involving increased distal femoral resection and/or posterior capsular release. Adequate FFD correction is critical for functional outcome.
2. Meticulous Soft Tissue Balancing:
   • Varus Knees: Systematically release the medial structures (deep MCL, semimembranosus, posteromedial capsule) in a stepwise fashion to achieve a rectangular and symmetrical extension gap. Prioritize the extension gap first, then the flexion gap. Avoid over-release, which can lead to instability.
   • Valgus Knees: Lateral releases are required (popliteus tendon, lateral collateral ligament, posterolateral capsule, IT band). Always be cognizant of the peroneal nerve.
   • Flexion vs. Extension Gap: The goal is to create equal and rectangular flexion and extension gaps. Flexion gap is primarily determined by posterior femoral cuts and rotation; extension gap by distal femoral and proximal tibial cuts and soft tissue releases.
3. Accurate Bone Cuts & Referencing:
   • Mechanical Axis Restoration: The primary goal of TKA. The tibial cut should be perpendicular to the mechanical axis; the femoral cut must incorporate the appropriate valgus angle.
   • Femoral Component External Rotation: A 3-5° external rotation relative to the posterior condylar axis or perpendicular to the epicondylar axis is crucial for proper patellar tracking and balancing the flexion gap. Do not use the anteroposterior (AP) axis in severe varus/valgus knees as a reliable reference.
   • Tibial Slope: A 3-7° posterior tibial slope is typically desired for optimal kinematics.
4. Patellar Management:
   • Resurfacing Decision: Based on patellar cartilage quality, patient symptoms, and surgeon preference. If resurfacing, ensure adequate and symmetrical bone resection.
   • Tracking Assessment: Always check patellar tracking with trial components in place using the "no-thumb" test. If maltracking occurs, consider lateral retinacular release (judiciously to avoid avascular necrosis of the patella).
5. Multi-Modal Pain Management: Early and effective pain control is crucial for patient comfort, early mobilization, and compliance with physical therapy, thereby improving functional outcomes and reducing complications like arthrofibrosis.
6. Prophylaxis against Complications: Strict adherence to DVT prophylaxis protocols, meticulous sterile technique to prevent infection, and appropriate perioperative antibiotic administration.

Pitfalls to Avoid in Total Knee Arthroplasty:

1. Inadequate Pre-operative Assessment:
   • Skipping Full-Length Radiographs: Leads to inaccurate assessment of the mechanical axis and can result in implant malposition and suboptimal outcomes.
   • Missing Severe Bone Loss/Deformity: Failure to recognize severe bone defects or extreme deformities can lead to intraoperative surprises, inadequate implant selection, and compromise stability.
2. Aggressive or Insufficient Soft Tissue Release:
   • Over-release: Results in instability (e.g., medial over-release in varus knee leading to valgus instability), requiring constrained implants or revision.
   • Under-release: Leads to persistent deformity (e.g., residual varus), stiffness, and pain.
3. Incorrect Component Alignment/Rotation:
   • Malalignment: Deviations from the neutral mechanical axis (e.g., persistent varus/valgus) accelerate implant wear, increase the risk of loosening, and lead to early failure.
   • Internal Femoral Rotation: A common pitfall. Leads to patellar maltracking, lateral patellar subluxation, and retropatellar pain.
4. Flexion-Extension Gap Mismatch:
   • Tight in Extension, Loose in Flexion: Often due to insufficient distal femoral resection or inadequate posterior capsular/osteophyte removal.
   • Loose in Extension, Tight in Flexion: Can occur with excessive distal femoral resection or inadequate posterior femoral cuts. Leads to instability or inability to achieve full flexion.
5. Patellar Complications:
   • Over-Resection: Can lead to patellar fracture or avascular necrosis.
   • Under-Resection: Can cause continued patellofemoral pain and difficulty with tracking.
   • Aggressive Lateral Release: Risk of patellar denervation and avascular necrosis.
6. Poor Cementation Technique:
   • Inadequate Bone Preparation: Residual blood, fat, or cartilage on bone surfaces impairs cement penetration and bonding.
   • Insufficient Cement Mantle or Porosity: Leads to early aseptic loosening.
   • Extravasation: Excess cement can impinge on neurovascular structures.
7. Inadequate Post-operative Rehabilitation:
   • Failure to Address Fixed Flexion Deformity: If not corrected surgically, aggressive post-op efforts are needed to stretch the posterior capsule.
   • Poor Pain Control: Hinders patient participation in PT, leading to stiffness and poor outcomes.
   • Lack of Patient Compliance: Crucial for achieving optimal range of motion and strength.

Adherence to these pearls and conscious avoidance of these pitfalls will significantly enhance the probability of a successful outcome in total knee arthroplasty for patients with end-stage osteoarthritis.