Prehabilitation in Total Knee Arthroplasty

Original Editor - Stacy Schiurring based on the course by Joretha Steyn
Top Contributors - Stacy Schiurring and Jess Bell

Introduction

Prehabilitation is a proactive, structured programme designed to improve a patient's physical and psychological capacity before surgery. Unlike rehabilitation, which aims to restore function after an injury or operation has occurred, prehabilitation focuses on enhancing physiological reserve prior to the surgical stress. Together, prehabilitation and rehabilitation form a continuum of care; one preventing functional loss, the other restoring it.

Prehabilitation typically occurs between two and eight weeks prior to surgery, though optimal timing remains a subject of ongoing research. The primary goals include enhancing physiological reserve (muscle strength, aerobic capacity, flexibility), improving psychological preparedness and reducing anxiety, preventing or minimising post-operative functional decline, reducing post-operative complications, and maintaining or improving baseline function.

The physiological mechanisms underlying prehabilitation include building muscle strength and neuromuscular control that provide a buffer to handle surgical stress and the subsequent immobilisation. Psychologically, prehabilitation addresses anxiety, improves motivation, and enhances self-efficacy before the operation.

This Physiopedia page explores the use of prehabilitation for patients prior to total knee arthroplasty (TKA), examining the current evidence for its effectiveness, appropriate patient selection, outcome measures for assessment, and how surgical and anaesthetic factors influence rehabilitation outcomes.

Current Evidence for Prehabilitation Effectiveness

Systematic reviews indicate that prehabilitation shows promise for patients undergoing TKA, but the overall strength of evidence remains low to moderate. Heterogeneity in intervention protocols, small sample sizes, and methodological limitations across studies limit firm conclusions. That said, evidence from randomised controlled trials suggests prehabilitation may result in increased strength and reduced length of stay.

Table 1. Summary of Prehabilitation Outcomes

Outcome	Effect	Evidence
Pain relief	Improves	Significant pain reduction at 1, 3, and 6 months post-surgery (SMD = 0.44, 95% CI: 0.17-0.71)
Muscle strength	Improves	Moderate to large effect size (SMD = 0.72, 95% CI: 0.47-0.98). High-intensity training (≥70% 1-RM) is particularly effective
Physical function	Improves	Patient-reported function improves post-operatively (SMD = 0.50, 95% CI: 0.23-0.77)
Quality of life	Improves	Health-related quality of life improves (SMD = 0.28, 95% CI: 0.12-0.43). Pre-operative mental health shows significant improvement (SF-36 MCS: 48.17 ± 9.28 vs 39.66 ± 12.28, p = 0.01)
Range of motion	Mixed	Some studies show modest improvements (SMD = 0.31, 95% CI: 0.02-0.59), but others report little effect in the medium to long term
Length of hospital stay	Inconsistent	Little consistent effect demonstrated, though individual patient factors and protocols influence this outcome
Long-term function (>6 months)	Limited	Benefits appear to diminish by 3-6 months post-operatively. Prehabilitation may accelerate recovery rather than alter long-term outcomes
Activities of daily living	No clear benefit	Comparable to usual care with no clear superiority demonstrated

SMD = Standardised Mean Difference; CI = Confidence Interval; SF = Survival Function; MCS = Model Confidence Set; p = probability value (p-set)

Patient Selection for Prehabilitation

Not all patients get equal benefit from prehabilitation programmes. Recent evidence suggests that prehabilitation may be most beneficial for patients at risk of poor outcomes following total TKA. Systematic reviews have identified several risk factors associated with poorer outcomes following TKA, suggesting that these patients should be prioritised for targeted prehabilitation interventions.

Physical Factors. Patients with severe pre-operative knee range of motion deficits (particularly <30° extension deficit or <75° flexion), significant functional limitations at baseline, poor baseline quadriceps strength, high body mass index (BMI), frailty or advanced age, and central sensitisation show greater benefit from prehabilitation programmes.

Psychological Factors. Prehabilitation may be particularly valuable for patients experiencing anxiety or depression, pain catastrophising, low self-efficacy, or poor mental health status, as these factors can negatively impact post-operative outcomes.

Medical Comorbidities. Candidates for targeted prehabilitation include patients with multiple comorbidities that may limit post-operative rehabilitation, cardiovascular or respiratory conditions affecting exercise tolerance, or neurological conditions affecting mobility.

Clinical practice guidelines recommend against delaying surgery specifically to complete prehabilitation for most patients, as delays may cause increased pain due to disease severity. However, exceptions include non-ambulatory patients who may benefit from improving mobility before surgery, patients recovering from significant medical events (e.g. stroke) that may limit post-operative rehabilitation, and patients with major lower extremity weakness who could improve their functional baseline. The emphasis is on utilising the waiting period productively rather than extending it.

Outcome Measures for Assessment and Prognosis

Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). The WOMAC is a widely validated outcome measure consisting of 24 items across three dimensions: pain (5 items), stiffness (2 items), and physical function (17 items). Each item is scored from 0 (none) to 4 (extreme), with a maximum total score of 96 (often transformed to a percentage). Higher scores indicate greater impairment. The WOMAC is highly predictive of treatment success one year post-operatively, making it valuable for identifying appropriate surgical candidates and tracking outcomes.

Knee Injury and Osteoarthritis Outcome Score (KOOS). The KOOS contains 42 items across five dimensions: pain (9 items), symptoms (7 items), activities of daily living (17 items), sport and recreation function (5 items), and quality of life (4 items). Items are scored from 0 (no problems) to 4 (extreme problems) and transformed to a 100-point scale where lower scores indicate greater impairment. The KOOS provides a more comprehensive assessment than the WOMAC, particularly for younger, more active patients.

Pre-operative Physical Assessment as Prognostic Indicators

Pre-operative assessment of physical function provides valuable prognostic information for post-operative outcomes and helps identify patients who will benefit most from targeted prehabilitation interventions. Each of these assessments can be easily completed at the bedside. Table 2 lists bedside assessments and their prognostic value.

Table 2. Physical Assessment Prognostic Indicators

Assessment Parameter	Prognostic Value	Key Findings	Clinical Implications
Quadriceps strength	Strongest predictor	• Accounts for the bulk of variance in 1-year stair climbing and timed up and go (TUG) performance • Pre-operative pain and knee range of motion (ROM) are poor predictors by comparison • Shows positive association with post-operative function across multiple time points	• Patients with osteoarthritis (OA) have ~35% lower knee extensor strength vs age-matched controls • 60-80% of remaining strength is lost immediately post-operatively • A 30-40% strength increase is needed for improved post-operative function and pain reduction • Strengthening exercises during prehabilitation are essential to establish a higher baseline
Extension deficit	Strong predictor	• A pre-operative knee extension deficit of 30° = 100% specificity for predicting poor post-operative extension (>10°) and flexion (<100°)	• Pre-operative knee flexion contractures affect post-operative knee ROM • Hamstring stretching before and after surgery increases ROM and may decrease medial thigh pain post-operatively
Flexion range	Moderate predictor	• If pre-operative knee flexion is <75°, there are no substantial improvements at 1 year post-surgery	• Maximise pre-operative ROM through stretching and mobility exercises • It is important to set realistic expectations for patients with severe flexion deficits

Surgical and Anaesthetic Factors Affecting Rehabilitation

Understanding surgical and anaesthetic approaches helps physiotherapists set appropriate expectations, modify treatment protocols, and anticipate recovery trajectories. The following tables summarise key factors that influence early rehabilitation.

Table 3. Surgical Approaches

Approach	Technique	Impact on Rehabilitation	Early Recovery Expectations
Medial parapatellar (traditional)	Incision through the quadriceps tendon and vastus medialis oblique (VMO); patellar eversion; 12-14 cm incision	Extensive extensor mechanism damage; slower quadriceps recovery; more post-operative pain	Longer time to achieve active straight leg raise (SLR); standard 5-7 day discharge; 6-week crutch use
Mid-vastus	Spares quadriceps tendon; dissects through VMO; preserves VMO insertion	Moderate muscle preservation; faster recovery than traditional	Intermediate recovery timeline; reduced complications vs traditional
Sub-vastus (quadriceps-sparing)	Complete quadriceps and VMO sparing; dissection underneath VMO; 10-12 cm incision	Minimal extensor mechanism trauma; 40% less pain medication; faster SLR recovery; improved ROM at 1-2 weeks	24-48 hour discharge possible; 2-week crutch use; similar outcomes to traditional by 6 weeks
Tourniquet use	Pressure cuff applied to thigh (250 mmHg, ≤2 hours) during surgery	Muscle ischaemia-reperfusion injury; impaired quadriceps activation; increased pain, swelling, and DVT risk (21.5% vs 8%)	Anticipate: higher pain levels, difficulty with SLR, slower ROM progression (first 2-3 weeks), need for aggressive pain management and extended warm-up periods

Key clinical point: Discuss the planned surgical approach and tourniquet use with patients during prehabilitation to set realistic expectations. Post-operatively, confirm these details as they significantly influence rehabilitation progression.

Table 4. Anaesthetic Considerations

Type	Characteristics	Rehabilitation Impact	Critical Safety Considerations
General anaesthesia	Patient is unconscious throughout surgery	Less pain at 6 and 24 hours; less dizziness post-operatively; shorter hospital stays; decreased opioid need	Earlier mobilisation is typically safe; standard precautions apply
Spinal/regional anaesthesia	Nerve block below the waist; patient is awake or sedated	Less immediate pain; more nausea at 24 hours; overall less pain post-operatively	Always verify active SLR before mobilisation. If the patient cannot engage their quadriceps (i.e. the nerve block is still active), their knee will give way during weight-bearing. This is particularly important for early mobilisation (2-4 hours post-operatively)
Opioid-sparing protocols	Multimodal approach: local infiltration, nerve blocks, NSAIDs, acetaminophen (paracetamol)	Less dizziness, nausea, orthostatic hypotension, and sedation	Facilitates earlier and safer mobilisation; improved patient alertness for therapy

Modern surgical and anaesthetic techniques have enabled accelerated discharge protocols, with some patients discharged within 24-48 hours or even the same day. Success depends on quadriceps-sparing surgical approaches, multimodal opioid-sparing analgesia, absence of drains and catheters, early mobilisation, and comprehensive prehabilitation. These accelerated protocols make prehabilitation even more critical—patients must be physically and psychologically prepared to safely manage a rapid discharge home.

Prehabilitation Exercise Programming

While no single "optimal" exercise prescription has been definitively established, core components are associated with successful outcomes.

Evidence-Based Exercise Components

Strengthening Exercises. Progressive resistance training targeting the quadriceps, hamstrings, and hip musculature forms the foundation of prehabilitation. High-intensity protocols (≥70% of one-repetition maximum) appear most effective if patients can tolerate them. Key exercises include isometric quadriceps contractions, active straight leg raises, hip abduction, knee extension (seated and supine), and squats (modified depth as tolerated).

Range of Motion and Flexibility. Maintaining or improving pre-operative ROM, particularly into full extension, is crucial. Hamstring flexibility significantly affects a person's ability to achieve full knee extension. Essential exercises include heel slides for knee flexion, prone or supine knee extension stretches, and hamstring stretching.

Aerobic Conditioning. Walking and cycling programmes improve cardiovascular fitness and may reduce length of stay. While walking is beneficial, it should not be considered sufficient on its own as specific strengthening exercises remain essential.

Balance and Proprioception. Single-leg stance exercises on the unaffected leg (progressing to the affected leg pre-operatively if tolerated) improve balance and prepare patients for post-operative mobility.

Functional Task Training. Practising bed mobility, transfers, stair climbing, and assistive device use before surgery improves confidence and recall in the post-operative period when pain and medication may impair learning.

Programme Duration and Frequency

Most successful prehabilitation programmes range from 2-8 weeks in duration, with sessions typically conducted 2-3 times per week for supervised programmes, supplemented by daily home exercise. High-intensity programmes may show greater benefits but require appropriate patient selection and monitoring.

Delivery Models

Prehabilitation can be delivered through supervised outpatient sessions (gym- or clinic-based), home-based programmes with periodic check-ins, telerehabilitation (shown to have similar effects to in-person care), or combination approaches. Evidence suggests gym-based, supervised prehabilitation may be most effective, though home-based programmes offer greater accessibility.

Discharge Criteria and Functional Outcomes

Regardless of length of stay, patients should meet specific criteria before discharge to ensure a safe transition to home.

Pain Management. Pain must be adequately controlled with an oral medication regimen that allows functional activity.

Functional Mobility. Patients must demonstrate independent bed mobility (including lying-to-sitting transitions), independent transfers (sit to stand, toilet and shower transfers), independent ambulation with an appropriate assistive device to the bathroom, and the ability to manage a few stairs (even if the patient doesn't have stairs at home).

Exercise Performance. Patients must demonstrate that they can perform isometric quadriceps contractions, achieving full knee extension, active straight leg raises without an extensor lag, hip abduction in supine (which assists with car transfers), and knee flexion of at least 90° in sitting and 60-70° in supine. Functional strength should be at least grade 3 on the Oxford muscle grading scale.

Psychological Readiness. Patients must feel willing and ready to go home and feel safe doing so. Psychological preparedness is as important as physical capability for successful recovery.

Resources

• Brophy RH, Fillingham YA. AAOS clinical practice guideline summary: management of osteoarthritis of the knee (nonarthroplasty). JAAOS-Journal of the American Academy of Orthopaedic Surgeons. 2022 May 1;30(9):e721-9.
• Jette DU, Hunter SJ, Burkett L, Langham B, Logerstedt DS, Piuzzi NS, Poirier NM, Radach LJ, Ritter JE, Scalzitti DA, Stevens-Lapsley JE. Physical therapist management of total knee arthroplasty. Physical therapy. 2020 Sep;100(9):1603-31.
• Optimal Timing of Total Hip and Knee Arthroplasty. American College of Rheumatology, 2023.