TKA INDICATIONS
Patient Selection | Failed Conservative | Surgical Timing
TKA Indications Classification
Critical Must-Knows
- Primary OA is most common indication (95% of TKAs)
- Failed conservative management is prerequisite for surgery
- Radiographic severity must correlate with clinical symptoms
- Patient expectations are critical for satisfaction
- Absolute contraindications: Active infection, severe vascular disease
Examiner's Pearls
- "Kellgren-Lawrence Grade 3-4 correlates with surgical candidacy
- "Night pain and rest pain suggest advanced disease
- "BMI greater than 40 increases complications but not absolute contraindication
- "Age extremes require careful counseling regarding outcomes and revision risk
Critical TKA Indication Exam Points
Appropriate Indications
Pain and functional limitation refractory to conservative management including analgesia, physiotherapy, weight loss, injections. Radiographic OA with joint space narrowing, osteophytes, subchondral sclerosis correlating with symptoms.
Contraindications
Absolute: Active sepsis, remote infection, severe peripheral vascular disease, neuropathic joint. Relative: Morbid obesity (BMI greater than 40), poorly controlled diabetes (HbA1c greater than 8), immunocompromise, unrealistic expectations.
Conservative Trial
Minimum 3-6 months of non-operative treatment before considering surgery. Includes weight loss, physiotherapy, activity modification, analgesia (paracetamol, NSAIDs), walking aids, bracing, intra-articular injections (corticosteroid, hyaluronic acid).
Patient Selection
Optimal candidates: Older than 55, unilateral disease, non-obese, motivated, realistic expectations. Higher risk: Younger than 55 (revision risk), morbid obesity, smokers, poorly controlled comorbidities, workers compensation claims.
At a Glance
Total knee arthroplasty (TKA) is indicated for end-stage knee arthritis with pain and functional limitation refractory to conservative management (minimum 3-6 months trial). Primary osteoarthritis accounts for 95% of TKAs, with Kellgren-Lawrence Grade 3-4 radiographic changes that correlate with clinical symptoms. Absolute contraindications include active infection and severe peripheral vascular disease; relative contraindications include morbid obesity (BMI over 40), poorly controlled diabetes (HbA1c over 8), and unrealistic expectations. Optimal candidates are over 55 years, non-obese, motivated, and have realistic expectations. TKA achieves 95% 10-year survivorship and 85% patient satisfaction when patient selection is appropriate. Night pain and rest pain suggest advanced disease warranting surgical consideration.
ARTHRITISTKA Indication Checklist
Memory Hook:ARTHRITIS criteria must be met before TKA!
STINGAbsolute Contraindications
Memory Hook:STING means no TKA until resolved!
OBESERelative Contraindications
Memory Hook:OBESE patients need optimization before TKA!
Overview
Total knee arthroplasty is one of the most successful orthopaedic procedures, providing reliable pain relief and functional improvement for end-stage knee arthritis. Appropriate patient selection is critical for optimal outcomes, as up to 15-20% of patients remain dissatisfied despite technically successful surgery.
Historical Perspective
Modern TKA has evolved significantly since the 1970s. The development of constrained designs, improved polyethylene, and standardized surgical techniques has resulted in excellent long-term survivorship. Current focus is on optimizing patient selection and managing expectations.
Epidemiology
Knee osteoarthritis affects approximately 250 million people worldwide. The demand for TKA continues to rise with aging populations and increasing obesity prevalence. Australia performs approximately 65,000 knee replacements annually according to AOANJRR data.
Pathophysiology of Knee Arthritis
Osteoarthritis
Primary osteoarthritis is a disease of articular cartilage with progressive loss of hyaline cartilage, subchondral bone changes, osteophyte formation, and synovial inflammation. The process is irreversible once bone-on-bone contact occurs.
Inflammatory Arthritis
Rheumatoid arthritis and other inflammatory conditions cause synovial hypertrophy with pannus formation, leading to cartilage destruction, bone erosion, and ligamentous instability. Medical management with DMARDs has reduced but not eliminated the need for TKA.
Secondary Causes
Post-traumatic arthritis following tibial plateau fractures, ligament injuries, or meniscectomy represents a significant proportion of younger TKA patients. Osteonecrosis, crystal arthropathies, and hemophilic arthropathy are less common causes.
Radiographic Correlation
Clinical-radiographic correlation is essential. Some patients with severe radiographic OA have minimal symptoms, while others with mild changes have significant pain. The indication for TKA is failed conservative management of symptomatic arthritis, not radiographic severity alone.
Classification Systems
Kellgren-Lawrence Radiographic Classification
The most widely used grading system for knee osteoarthritis severity based on weight-bearing radiographs.
Kellgren-Lawrence Classification
| Grade | Radiographic Findings | Clinical Correlation | Surgical Candidacy |
|---|---|---|---|
| Grade 0 | No features of OA | Normal knee | No indication |
| Grade 1 | Doubtful JSN, possible osteophytes | Minimal symptoms | Conservative management |
| Grade 2 | Definite osteophytes, possible JSN | Mild-moderate symptoms | Conservative, possibly UKA |
| Grade 3 | Moderate osteophytes, definite JSN, sclerosis | Moderate symptoms | Consider TKA if failed conservative |
| Grade 4 | Large osteophytes, severe JSN, bone-on-bone | Severe symptoms | TKA candidate |
The Kellgren-Lawrence classification provides standardized grading for radiographic osteoarthritis severity.
Bone-on-Bone Not Required
TKA does not require bone-on-bone contact. KL Grade 3 with failed conservative management and significant symptoms is an appropriate indication. However, milder grades should exhaust conservative options and may be suitable for osteotomy or UKA.
Clinical Relevance and Patient Selection
Absolute Indications
The primary indication for TKA is end-stage knee arthritis with failed conservative management characterized by:
- Significant pain affecting quality of life
- Functional limitation (walking distance, stairs, ADLs)
- Night pain and rest pain
- Radiographic changes correlating with symptoms
- Failure of at least 3-6 months conservative care
Specific Conditions
Primary osteoarthritis accounts for approximately 95% of TKAs. Other indications include rheumatoid arthritis, post-traumatic arthritis, osteonecrosis, and crystalline arthropathy. Each requires individualized assessment.
This comprehensive evaluation ensures appropriate patient selection.
Conservative Management Trial
Conservative Management Options
| Modality | Evidence Level | Expected Benefit | Duration/Dose |
|---|---|---|---|
| Weight loss | Level I | Significant pain reduction per 5kg lost | 5-10% body weight target |
| Physiotherapy | Level I | Strength, proprioception, function | 6-12 weeks supervised program |
| Paracetamol | Level I | Mild pain relief, safe long-term | 1g QID maximum 4g daily |
| NSAIDs | Level I | Moderate pain relief | Lowest effective dose, GI protection |
| Intra-articular steroid | Level I | Short-term relief 4-8 weeks | Maximum 3-4 per year |
| Hyaluronic acid | Level II | Controversial, modest benefit | 3-5 weekly injections |
| Bracing | Level II | Unloading affected compartment | Continuous use during activity |
When Conservative Fails
Conservative management is considered failed when adequate trials of multiple modalities over 3-6 months fail to provide sufficient pain relief or functional improvement. Night pain and rest pain are particularly indicative of advanced disease requiring surgery.
Special Populations
Young Patients (Under 55)
Younger patients have higher activity demands and longer life expectancy, resulting in:
- Higher revision rates (15-20% at 15 years vs 5-10% in older patients)
- Need for realistic expectations about activity limitations
- Consideration of alternative procedures (osteotomy, UKA)
- Discussion of future revision surgery likelihood
Elderly Patients (Over 80)
Older patients have higher perioperative medical risks but excellent pain relief outcomes. Considerations include:
- Medical optimization essential
- Higher cardiac and pulmonary complication rates
- Excellent functional improvement despite comorbidities
- Single-stage bilateral TKA generally avoided
Morbid Obesity
BMI greater than 40 increases surgical complications:
- Surgical site infection increased 2-3 fold
- DVT and PE risk elevated
- Implant loosening rates higher
- Weight loss programs beneficial but surgery not contraindicated
Investigations
Preoperative Workup
Imaging:
- Weight-bearing AP, lateral, skyline radiographs
- Long-leg alignment films (if deformity)
- MRI rarely needed (unless diagnostic uncertainty)
Bloods:
- FBC, UEC, LFTs, coagulation
- HbA1c (diabetics, target less than 8%)
- CRP/ESR (rule out infection if suspected)
Preoperative Investigations
| Investigation | Purpose | Target |
|---|---|---|
| HbA1c | Glycemic control | Less than 8% |
| Vitamin D | Bone health | Greater than 75 nmol/L |
| Albumin | Nutritional status | Greater than 35 g/L |
| ECG | Cardiac assessment | No acute changes |
Management Algorithm
Decision Making
Step 1: Confirm Diagnosis
- Radiographic OA with symptom correlation
- Exclude other causes (infection, referred pain)
Step 2: Conservative Trial
- Minimum 3-6 months
- Weight loss, physiotherapy, analgesia, injections
Step 3: Patient Selection
- Assess contraindications
- Optimize modifiable risk factors
Management Pathway
| Stage | Action | Duration |
|---|---|---|
| Initial | Conservative management | 3-6 months |
| Optimization | Risk factor modification | Variable |
| Surgical | TKA if failed conservative | When optimized |
Surgical Approach Overview
Standard Approaches
Medial Parapatellar:
- Most common approach
- Good exposure, extensile
- Standard for most primary TKA
Other Approaches:
- Subvastus (less quadriceps disruption)
- Midvastus (compromise approach)
- Lateral (valgus deformity)
Surgical Approaches
| Approach | Indication | Advantage |
|---|---|---|
| Medial parapatellar | Standard primary TKA | Excellent exposure |
| Subvastus | Selected patients | Less quad damage |
| Lateral | Valgus deformity | Better lateral access |
Complications
Potential Complications
Early:
- Surgical site infection (1-2%)
- DVT/PE (1-2% symptomatic)
- Stiffness (5-10%)
- Wound problems (2-5%)
Late:
- Aseptic loosening (1% per year)
- Periprosthetic fracture (1-2%)
- Late infection (0.5% per year)
- Polyethylene wear
Complication Rates
| Complication | Incidence | Prevention |
|---|---|---|
| Infection | 1-2% | Optimization, prophylaxis |
| DVT | 1-2% symptomatic | Chemoprophylaxis |
| Stiffness | 5-10% | Early mobilization, PT |
| Loosening | 5% at 10 years | Technique, alignment |
Postoperative Care
Recovery Protocol
Immediate (0-6 weeks):
- Full weight-bearing with walker/crutches
- DVT prophylaxis (2-6 weeks)
- Physiotherapy for ROM and strength
- Wound care
Early (6-12 weeks):
- Progress to independent walking
- Return to sedentary activities
- Continue physiotherapy
Recovery Timeline
| Timeframe | Activity | Goals |
|---|---|---|
| 0-6 weeks | Protected walking | ROM 0-90° |
| 6-12 weeks | Independent ambulation | Full extension |
| 3-6 months | Light activities | ROM 0-120° |
Outcomes
Expected Results
Survivorship:
- 95% at 10 years
- 90% at 15 years
- 85% at 20 years
Patient Satisfaction:
- 85% satisfied overall
- 15-20% have residual dissatisfaction
- Expectations predict satisfaction
Outcome Data
| Measure | Result | Comment |
|---|---|---|
| 10-year survival | 95% | AOANJRR data |
| Satisfaction | 85% | Patient selection critical |
| Return to sport | Variable | Low-impact only |
| Pain relief | 90%+ | Most reliable outcome |
Evidence Base
- 19% of TKA patients dissatisfied at 1 year
- Expectations and mental health predict satisfaction
- Surgical technique not main determinant of satisfaction
- Patient selection critical for outcomes
- 65,000 knee replacements annually in Australia
- 10-year revision rate approximately 5%
- Primary OA accounts for 95% of procedures
- Younger patients have higher revision rates
- Recommend conservative management trial before surgery
- No BMI threshold but optimization encouraged
- Shared decision-making with realistic expectations
- Multidisciplinary preoperative assessment
- BMI greater than 40 associated with 2x infection risk
- Weight loss programs beneficial but outcomes still good
- Should not deny surgery solely based on BMI
- Optimization preferable to arbitrary cutoffs
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
Scenario 1: Standard TKA Indication
"A 68-year-old woman presents with bilateral knee pain worse on the right for 5 years. She has tried physiotherapy, NSAIDs, and two cortisone injections without lasting relief. X-rays show KL Grade 4 changes on the right. What are your thoughts on surgical management?"
Scenario 2: Young Patient
"A 52-year-old builder presents with severe right knee pain limiting his ability to work. He has post-traumatic OA following tibial plateau fracture 15 years ago. Failed all conservative measures. What are your considerations?"
Scenario 3: Contraindications
"A 72-year-old diabetic man with BMI 42 and recurrent UTIs requests TKA for severe OA. His HbA1c is 9.2% and he is an active smoker. How do you approach this case?"
MCQ Practice Points
Primary Indication for TKA
Q: What is the most common indication for total knee arthroplasty? A: Primary osteoarthritis accounts for approximately 95% of TKA procedures. The key requirement is end-stage arthritis with failed conservative management over 3-6 months, not radiographic severity alone.
Absolute Contraindications
Q: What are the absolute contraindications to TKA? A: Remember STING: Sepsis/active infection (local or remote), Tuberculosis or remote infection, Ischemic limb (severe PVD), Neuropathic joint (Charcot), Generally unfit for surgery. Active infection is the most critical - never proceed with untreated UTI, dental abscess, or skin infection.
Radiographic Correlation
Q: Is Kellgren-Lawrence Grade 4 required for TKA? A: No. KL Grade 3 with significant symptoms and failed conservative management is an appropriate indication. The indication is symptomatic arthritis with failed conservative care, not radiographic severity alone. Some patients with KL4 have minimal symptoms and don't need surgery.
Glycemic Control
Q: What HbA1c threshold should be achieved before elective TKA? A: Target HbA1c less than 8%, ideally less than 7.5%. Perioperative glucose should be maintained below 10 mmol/L. Poor glycemic control increases surgical site infection risk threefold.
Australian Context
AOANJRR Data: The Australian registry provides excellent long-term outcome data. Current 10-year revision rates for primary TKA are approximately 5%, supporting the procedure's effectiveness. Higher revision rates in younger patients and those with inflammatory arthritis are well documented.
PBS Considerations: Perioperative medications including DVT prophylaxis and analgesics are PBS subsidized. Preoperative optimization through GP management is encouraged through chronic disease management plans.
Healthcare Access: TKA is available through both public and private sectors. Waiting times in public hospitals vary by state but generally 6-12 months for elective TKA.
Multidisciplinary Care: Australian practice emphasizes preoperative optimization through multidisciplinary clinics including physiotherapy, occupational therapy, and medical optimization.
TKA INDICATIONS
High-Yield Exam Summary
Key Indications
- •End-stage OA (KL Grade 3-4) with symptoms
- •Failed 3-6 months conservative management
- •Significant functional limitation and pain
- •Night pain and rest pain suggest advanced disease
Absolute Contraindications (STING)
- •Sepsis/active infection
- •TB or remote infection
- •Ischemic limb (severe PVD)
- •Neuropathic joint (Charcot)
- •Generally unfit for surgery
Relative Contraindications (OBESE)
- •Obesity morbid (BMI greater than 40)
- •Blood sugar uncontrolled (HbA1c greater than 8%)
- •Expectations unrealistic
- •Smoking active
- •Extreme youth (under 50)
Preop Optimization
- •HbA1c less than 8% (ideally under 7.5%)
- •Smoking cessation 4 plus weeks
- •Weight loss encouraged if obese
- •Dental clearance, treat infections