Who is responsible for the success or failure of a total knee replacement in terms of function and pain management?

Responsibility for Total Knee Replacement Outcomes

Success in total knee replacement is multifactorial, but the surgeon bears primary responsibility for technical execution and patient selection, while patient factors (comorbidities, expectations, psychological state) significantly influence pain outcomes—making painful TKA often a shared responsibility where neither party is solely "at fault."

The Reality of TKA Outcomes

Patient satisfaction rates for TKA range from 75% to 89%, meaning 10% to 30% of patients report ongoing pain or dissatisfaction despite technically successful surgery 1. This disconnect between surgical success and patient experience reveals the complexity of outcome attribution.

Technical Factors (Surgeon's Domain)

The surgeon controls critical technical elements that directly impact outcomes:

• Implant alignment and positioning - Malalignment contributes to failure, though navigation systems show no outcome difference 2
• Component selection - Choice between all-polyethylene versus modular tibial components (no difference in outcomes), and patellar resurfacing decisions (may decrease revision rates after 5 years) 2
• Surgical technique - Proper soft tissue balancing, bone preparation, and cement technique to prevent the most common failure mechanism: aseptic loosening (39.9% of revisions) 1, 2
• Infection prevention - Infection accounts for 27.4% of failures and is the leading cause of early revision (<2 years) 1, 2

Patient Selection (Shared Responsibility)

The surgeon must ensure appropriate patient selection, but patients must meet candidacy criteria:

• Radiographic evidence of moderate-to-severe osteoarthritis with documented joint damage 2
• Completion of at least one trial of nonoperative therapy (physical therapy, NSAIDs, intraarticular injections) without improvement 2
• Severe daily pain and radiographic joint space narrowing as consensus surgical indications 1

Patient Factors (Patient's Domain, But Often Uncontrollable)

Critical patient factors that predict poor outcomes include:

• Demographic factors: Female gender, older age, low socioeconomic status correlate with worse outcomes 3
• Medical comorbidities: Greater number of comorbidities and worse preoperative status are highly predictive of pain and disability 3
• Psychological factors: Depression, low self-efficacy, poor pain coping strategies, somatization, low social support, and unrealistic expectations contribute to poor outcomes 3
• Unmet expectations and functional limitations are major contributors to dissatisfaction 1

The Critical Caveat for Painful TKA

In cases of unexplained pain after TKA, reoperation is unwise and frequently associated with suboptimal results 1, 4, 2. This underscores that:

• Not all painful TKAs represent surgical failure
• Some pain is medically unexplained and may involve central sensitization (dysfunction of pain modulation by the central nervous system) 3
• 30% of patients report moderate pain at some stage by seven years post-operation, even with technically successful implants 5

Postoperative Rehabilitation (Shared Responsibility)

The patient must engage in rehabilitation, but the surgeon must prescribe it:

• Rehabilitation started on the day of TKA reduces hospital length of stay 2
• Strong evidence supports supervised exercise programs during the first 2 months after TKA to improve physical function 2
• Continuous passive motion does NOT improve outcomes and should not be used 2

The Bottom Line

For successful TKA with good function: Credit belongs primarily to proper surgical technique, appropriate patient selection, and patient engagement in rehabilitation—a collaborative achievement.

For painful TKA: Fault attribution depends on the cause:

• Surgeon's responsibility: Technical errors (malalignment, instability, infection from poor sterile technique)
• Shared responsibility: Inadequate patient selection when red flags were present
• Patient factors (not "fault"): Uncontrollable comorbidities, psychological factors, or central sensitization
• No one's fault: Medically unexplained pain despite optimal surgery and patient factors, which occurs in a significant minority

The evidence reveals that using revision as an endpoint makes all implants look similar (97.5% survival at 7 years), but using pain as an endpoint reveals significant differences and the reality that technical success does not guarantee pain-free outcomes 5.