Measuring High Level Activity After Total Hip Arthroplasty

Archival Presentation Notice: This article modernizes the multimedia presentation “Measuring High Level Activity After Total Hip Arthroplasty” originally presented by Thomas Parker Vail, MD (Professor and Chairman, Department of Orthopaedic Surgery, University of California, San Francisco; The Hip Society). The historical Flash lecture has been reconstructed into the synchronized video slide presentation above, with the original file preserved in the digital archives (measuring_high_level_activity_after_total_hip_arthroplasty.swf).

1. Introduction & The Paradigm Shift in Arthroplasty Demands

Total hip arthroplasty (THA) is widely recognized as one of the most successful surgical interventions in modern medicine, reliably restoring mobility and providing dramatic pain relief for patients with end-stage coxarthrosis. Historically, Sir John Charnley conceived low-friction arthroplasty as an operation for elderly, sedentary individuals with severe functional disability. Early postoperative regimens strictly limited physical activity to gentle, low-demand ambulation, cautioning patients against strenuous exertion to avoid premature mechanical loosening and catastrophic poly wear.

Over the past two decades, total hip arthroplasty has undergone a profound demographic and cultural transformation. Patients under the age of 65 now represent the fastest-growing surgical demographic, with contemporary registry projections indicating that young, active recipients will soon comprise more than 50% of all primary THA procedures. These younger cohorts do not define surgical success merely as the capacity to perform basic activities of daily living (ADLs) without pain. Instead, they expect a restored joint that accommodates vigorous recreational sports, rigorous endurance training, and demanding manual occupations.

This paradigm shift has introduced a fundamental clinical and biomechanical challenge. The systemic cardiovascular, metabolic, and psychological benefits of sustained physical activity are indisputable. However, physical activity introduces substantial mechanical demands across the prosthetic reconstruction. High-demand athletics amplify cyclic joint contact pressures, accelerate volumetric bearing wear, generate elevated frictional torques at modular taper junctions, and increase the risk of late traumatic dislocations or periprosthetic fractures. Accurately measuring and managing high-level physical activity is therefore essential for optimizing implant longevity and patient outcomes.

2. Limitations of Conventional Outcome Scores & The Ceiling Effect

The Ceiling Effect of Legacy Scoring Systems

Traditional patient-reported outcome measures (PROMs) were designed during the early development of arthroplasty to evaluate disability and recovery from severe joint impairment. Instruments such as the Harris Hip Score (HHS), the Oxford Hip Score (OHS), the Charnley Modified Postel-Merle d’Aubigné Score, and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) focus heavily on basic self-care and fundamental mobility tasks.

In contemporary, active cohorts, these legacy instruments demonstrate a severe ceiling effect. Items assessing whether an individual can put on shoes and socks, negotiate stairs using a handrail, or walk six blocks without resting fail to challenge higher-functioning patients. A large proportion of active patients achieve near-perfect or maximum scores (e.g., 95 to 100 on the Harris Hip Score) within several months following surgery. Consequently, these scores cannot distinguish a patient who ambulates quietly for thirty minutes each day from an athlete training for competitive tennis tournaments, distance cycling, or backcountry skiing.

Dissociation Between Subjective Satisfaction and Mechanical Loading

The ceiling effect masks critical differences in cumulative joint loading. Clinical scoring tools conflate symptomatic pain relief with functional capacity. A patient who achieves complete pain relief while leading a quiet, sedentary lifestyle receives an “excellent” score identical to that of a highly active marathon runner. This clinical dissociation presents major limitations for scientific investigation and implant surveillance. Wear, fatigue, and interface micro-motion are driven by actual physical loading cycles rather than subjective contentment. To evaluate the true durability of modern bearing couples and uncemented fixation surfaces, surgeons require dedicated, validated instruments capable of stratifying high-level activity.

3. Validated Patient-Reported Activity Scoring Instruments

The University of California, Los Angeles (UCLA) Activity Scale

To overcome the limitations of legacy instruments, Amstutz, Zahiri, and Schmalzried developed the UCLA Activity Scale. This 10-point scale stratifies joint replacement recipients from complete inactivity to regular participation in strenuous impact sports. Because of its brevity, reliability, and strong correlation with physical performance metrics, the UCLA Activity Scale has become the most widely reported activity instrument in arthroplasty literature.

The High-Activity Arthroplasty Score (HAAS)

Recognizing that a single-item metric like the UCLA scale may oversimplify athletic performance, Talbot and colleagues developed the High-Activity Arthroplasty Score (HAAS). The HAAS is a multi-item instrument designed to eliminate ceiling effects in young, active arthroplasty recipients by examining four specific functional domains: walking, running, stair climbing, and participation in strenuous sports or heavy vocational duties. Scores range from 0 (complete disability) to 18 (unrestricted high-performance function).

Prospective validation studies confirm that the HAAS exhibits a Gaussian distribution among patients under 60 years of age, without the left-skewed clustering typical of the Oxford Hip Score. Complementary patient-reported metrics include the Forgotten Joint Score (FJS-12), which assesses the frequency of joint awareness during high-demand physical tasks, and the Tegner Activity Scale, adapted from sports medicine to measure athletic participation levels.

4. Objective Activity Quantification: Accelerometers, Wearables & Gait Cycle Load

The Landmark John Charnley Award Study: Pedometer Data

While patient-reported scales provide valuable subjective data, they are vulnerable to recall bias, patient overestimation, and social desirability distortion. The seminal work of Schmalzried, Szuszczewicz, Northfield, and colleagues (awarded the 1998 John Charnley Award by The Hip Society) transformed arthroplasty biomechanics by introducing objective electronic pedometers to record continuous walking activity in joint replacement patients.

Schmalzried and co-investigators tracked daily walking cycles in 60 total joint arthroplasty recipients over prolonged surveillance periods. Their findings revealed three critical insights that redefined prosthetic tribology:

• High Mean Cumulative Usage: Patients averaged 1.9 million gait cycles per year (equivalent to approximately 3.8 million steps annually, or roughly 10,400 steps per day across active cohorts).
• Five-Fold Inter-Individual Variation: Objective usage varied widely among individuals, spanning from 0.8 million cycles per year in low-demand individuals to more than 4.2 million cycles per year in high-demand patients.
• Dissociation from Clinical Scores: Correlation between objective annual cycles and subjective Harris Hip Scores was weak (r = 0.28). Patients with identical, excellent clinical scores exhibited marked differences in actual mechanical joint cycles, proving that subjective clinical ratings cannot serve as proxies for in vivo wear cycles.

Modern Accelerometry, Wearables, and Dynamic Load Intensity

Contemporary digital health technologies have expanded beyond basic step counters to tri-axial accelerometers, high-frequency inertial measurement units (IMUs), and consumer smartwatches. These devices track raw step volume along with cadence dynamics (steps per minute), step regularity, acceleration peaks, and time spent in moderate-to-vigorous physical activity (MVPA).

Step counters capture gait frequency, but they do not capture joint load intensity. In vivo telemetric studies demonstrate that ground reaction forces and peak resultant joint contact pressures increase nonlinearly with gait velocity and cadence. A brisk walk at 120 steps per minute generates substantially greater hip contact forces than walking at 80 steps per minute. Modern wearable algorithms incorporate tri-axial vector magnitude measurements, providing an estimate of cumulative mechanical joint energy and impact loading throughout daily activities.

5. Hip Society & AAHKS Consensus on Return to Sports

The Consensus Framework

To establish standardized guidance for active patients, The Hip Society and the American Association of Hip and Knee Surgeons (AAHKS) surveyed experienced arthroplasty surgeons regarding athletic participation following total hip arthroplasty. Synthesized by Klein, Levine, Hozack, and colleagues, and corroborated by Healy et al., this consensus classifies athletic pursuits into three distinct clinical tiers:

Evolution of Clinical Perspectives

Surgeon recommendations have grown increasingly permissive over the past decade, influenced by the clinical durability of highly cross-linked polyethylene and ceramic articulations. While high-impact contact sports remain discouraged, many surgeons adopt a shared decision-making model for non-contact impact athletics such as jogging or singles tennis. This counseling balances the systemic cardiovascular benefits and personal fulfillment of the patient against potential risks of accelerated polyethylene oxidation, liner chipping, or early revision.

6. Biomechanical & Tribological Considerations in High-Demand Patients

In Vivo Dynamic Joint Reactive Forces

Direct in vivo telemetric data from Bergmann and the Charité group demonstrate that hip joint contact pressures vary widely depending on the nature of physical activity:

• Level Walking (Cadence 100 to 110 steps/min): Resultant hip contact forces range from 2.5 to 3.0 times body weight (BW).
• Stair Climbing: Contact loads peak at 3.5 to 4.2 times BW, with higher torsional and posterior shear components across the femoral component.
• Jogging and Running: Resultant forces spike to 5.5 to 8.0 times BW during foot strike and heel-off phases.
• Stumbling, Tripping, or Explosive Cutting: Sudden eccentric muscular contractions generate peak transient loads approaching 8.0 to 11.0 times BW.

Bearing Tribology: HXLPE vs. Ceramic Articulations

Historical conventional ultra-high-molecular-weight polyethylene (UHMWPE) sterilized in air generated linear wear rates of 0.1 to 0.25 mm per year and volumetric wear rates exceeding 100 mm³ per year. This wear pattern released billions of submicron particles, inducing macrophage-mediated foreign-body reactions, RANKL upregulation, periprosthetic osteolysis, and aseptic loosening. In high-demand patients logging millions of cycles, conventional polyethylene routinely failed within 7 to 12 years.

Highly cross-linked polyethylene (HXLPE), manufactured through gamma or electron-beam irradiation (50 to 100 kGy) followed by thermal processing or antioxidant stabilization (e.g., vitamin E blending), has reshaped arthroplasty outcomes. Cross-linking establishes covalent bonds between molecular chains, reducing in vitro and in vivo volumetric wear by 80% to 90% (linear wear rates <0.01 to 0.03 mm/year). Vitamin E diffusion preserves free radical resistance without requiring remelting, maintaining mechanical fatigue strength.

Ceramic-on-Ceramic (CoC) articulations eliminate polymer wear debris altogether, exhibiting fluid-film lubrication and in vivo volumetric wear rates under 1 mm³ per year. However, ceramic bearings introduce distinct technical and biological challenges:

• Brittle Fracture Risk: Although modern delta alumina-matrix composite ceramics have reduced fracture rates to 0.001%–0.02%, catastrophic shattering during high-impact athletic trauma remains a devastating complication.
• Stripe Wear and Edge Loading: In high-demand sports involving extreme ranges of motion, dynamic micro-separation and steep acetabular cup inclinations can cause edge loading, producing stripe wear and localized ceramic destruction.
• Audible Squeaking: Occurring in 1% to 3% of patients, squeaking results from disrupted fluid-film lubrication during high-frequency, repetitive motions.

Consequently, Ceramic-on-HXLPE (CoP) has become the most widely selected bearing couple for high-demand athletes. CoP combines the fracture resistance and modularity of cross-linked polyethylene with the low surface roughness (Ra <0.005 μm) and superior wettability of ceramic femoral heads, achieving minimal volumetric wear without squeaking or catastrophic liner fracture.

Femoral Head Diameter: Stability vs. Trunnion Taper Stresses

The choice of femoral head diameter involves balancing stability against frictional torque across the modular neck-stem taper junction. Larger femoral heads (32 mm and 36 mm) provide clear mechanical advantages for active patients:

• Increased Jump Distance: Jump distance (the lateral translation required before femoral head subluxation occurs) is calculated as r · cos(θ), where r is head radius and θ is the operative cup inclination angle. Increasing head diameter from 28 mm to 36 mm expands jump distance by approximately 28%, protecting against athletic subluxation.
• Expanded Impingement-Free Range of Motion: Increasing head diameter delays prosthetic neck-on-cup impingement by 15 to 25 degrees of excursion, allowing deep squats, pivoting, and extreme sports stances.

However, head diameters exceeding 36 mm (such as 40 mm or 44 mm) present specific trade-offs. Frictional torque increases linearly with head diameter. During high-velocity twisting maneuvers, elevated torque is transmitted directly to the 12/14 Morse trunnion taper. When paired with a cobalt-chromium head on a titanium stem, this shear stress promotes mechanically assisted crevice corrosion (MACC), fretting, and trunnionosis, triggering adverse local tissue reactions (ALTR) and pseudotumor formation. For high-demand patients, 36 mm ceramic heads—or the addition of an intermediate titanium sleeve (e.g., Biolox Option)—minimize trunnion fretting currents while maintaining joint stability.

7. Clinical Outcomes, Return Rates, and Long-Term Implant Survivorship

Evidence from Systematic Reviews and Meta-Analyses

Contemporary systematic reviews provide robust data regarding return-to-sports rates following total hip arthroplasty. In a comprehensive meta-analysis of 38 studies encompassing 8,542 patients by Pasqualini, Emara, Rullan, and colleagues (JBJS Rev 2023), the pooled overall return-to-sports rate was 84.6%. Among returning athletes, 81.2% participated at an equal or higher frequency compared to their preoperative status, and 76.5% resumed activities at an equal or higher intensity.

The average time required to resume regular athletic pursuits ranged from 4.8 to 6.2 months postoperatively. Return rates varied substantially by sport category:

• Low-Impact Athletics: Consistently demonstrated the highest resumption rates: swimming (>90%), stationary and outdoor cycling (>88%), golf (>85%), fitness walking (>92%), and doubles tennis (>80%).
• Intermediate Athletics: Alpine skiing exhibited a return rate of 70% to 80% among individuals with prior skiing experience, with most returning by the first winter season following surgery.
• High-Impact and Contact Sports: Maintained the lowest return rates, with jogging and running ranging from 30% to 50%, and competitive soccer or basketball below 35%. Most patients who ceased running cited surgeon counsel or fear of implant failure rather than joint discomfort.

Long-Term Survivorship in High-Activity Cohorts

Historically, registry data associated young age and male sex with elevated revision risks, driven primarily by polyethylene wear-induced osteolysis. In contrast, long-term studies using modern bearing articulations demonstrate durable survivorship in active populations. Shiomoto and colleagues (2023) evaluated matched cohorts of active THA recipients at a mean follow-up of 12.2 years. Despite maintaining an average daily step volume of 7,840 steps per day and high UCLA activity scores, the 12-year prosthesis survivorship free of aseptic loosening was 100% using contemporary highly cross-linked polyethylene and ceramic heads.

National registry data from Australia, the United Kingdom, and Scandinavia corroborate that when modern uncemented, highly porous acetabular components and HXLPE liners are employed in patients under 55 years of age, 15-year all-cause survivorship consistently exceeds 92% to 95%. These findings indicate that high-volume ambulation and active recreation do not precipitate early aseptic loosening when initial biological fixation is sound and wear debris remains below the critical osteolytic threshold.

8. Postoperative Athletic Rehabilitation & Progressive Return Protocols

Safe return to high-level athletics requires a criteria-based, four-phase rehabilitation protocol that prioritizes objective functional recovery over rigid calendar timelines:

Phase I: Acute Protection & Gait Normalization (Weeks 0 to 6)

Focuses on soft tissue healing, swelling resolution, and re-establishing non-antalgic ambulation. Patients maintain weight-bearing as tolerated using bilateral crutches or trekking poles until an unassisted, symmetric gait without a Trendelenburg lurch is demonstrated. Closed-chain isometric quadriceps and gluteal contractions begin immediately. Once surgical incisions are healed and active hip flexion reaches 90 degrees (typically week 3 to 4), low-resistance stationary cycling on an upright or recumbent bike is initiated to promote periarticular vascularity and joint lubrication.

Phase II: Neuromuscular Retraining & Dynamic Core Conditioning (Weeks 6 to 12)

Initiated once unassisted level walking is pain-free. Rehabilitation centers on progressive resistance training (PRT) targeting the hip abductor complex (gluteus medius and minimus), gluteus maximus, hamstrings, and lumbopelvic core musculature. Single-leg stance balance exercises and dynamic perturbation training on unstable foam platforms re-establish proprioceptive joint reflexes. Hydrotherapy and swimming using gentle flutter kicking (avoiding aggressive breaststroke whip kicks) provide cardiovascular conditioning without axial joint impact. Outdoor road cycling on flat pavement is introduced.

Phase III: Multi-Planar Agility & Sport-Specific Functional Drills (Months 3 to 6)

Focuses on dynamic coordination and controlled multi-directional movement. Patients progress through lateral band walks, ladder agility drills, and controlled change-of-direction movements. Sport-specific motor patterns are systematically reintroduced:

• Golf: Progressive swinging from chipping and putting to mid-irons, woods, and full driving off tees, with the front (lead) hip monitored for rotational shear.
• Tennis: Controlled stationary baseline groundstroke rallying with a practice partner, avoiding high-velocity sprinting and abrupt sliding.
• Skiing: Dry-land eccentric quadriceps conditioning, balance board training, and plyometric deceleration control.

Phase IV: Unrestricted Athletic Participation & Clearance Milestones (Month 6+)

Full return to unrestricted recreational athletics is permitted once objective clearance milestones are met:

• Limb Symmetry Index (LSI): Isokinetic or isometric dynamometry demonstrating operative abductor and extensor strength ≥85% to 90% of the contralateral, non-operative limb.
• Dynamic Balance Symmetry: Y-Balance Test anterior, posteromedial, and posterolateral reaching distances within 4 cm of the contralateral side.
• Single-Leg Squat Control: Performance of five consecutive single-leg squats without pelvic drop, trunk lean, or dynamic knee valgus collapse.
• Clinical Stability: Complete absence of post-activity joint effusion, groin discomfort, or mechanical clicking.

9. Complications, Failure Modes & Risk Mitigation Strategies

Athletic Impingement and Late Dislocation

High-demand athletics subject the prosthetic hip to extreme functional arcs of motion. Dislocation in active patients typically occurs when extreme athletic postures force the prosthetic neck to impinge against the acetabular rim or prominent bony osteophytes, levering the femoral head out of the socket. In yoga, martial arts, or gymnastics, extreme flexion and internal rotation risk posterior dislocation, whereas extreme extension, adduction, and external rotation (such as during skiing recoveries or aggressive dance maneuvers) risk anterior dislocation.

Mitigation Strategy: Achieve anatomical component orientation tailored to the patient’s individual functional spinopelvic mobility. Target the combined anteversion safe zone (35 to 45 degrees) and utilize a 36 mm femoral head to expand jump distance and delay prosthetic impingement. For athletes requiring extreme flexibility, high-offset femoral stems restore abductor tension and improve soft tissue clearance, preventing osseous impingement.

High-Velocity Traumatic Periprosthetic Fractures

Participation in high-velocity sports (alpine skiing, cycling, equestrian riding) carries inherent risks of high-energy falls. In active patients with well-fixed uncemented stems, traumatic falls often produce Vancouver B1 (stem well-fixed, fracture adjacent to prosthesis) or Vancouver B2 fractures (stem loose, compromised host bone).

Mitigation Strategy: Educate active patients on sports safety, trail selection (avoiding icy or hazardous conditions), and protective equipment. Screen and optimize bone mineral density in high-risk patients. Ensure adequate diaphyseal bypass and circumferential cortical contact during index stem selection, avoiding anterior cortical encroachment or aggressive reaming in stiff bone.

Iliopsoas Impingement and Tendinopathy

Repetitive hip flexion in activities like road cycling, rowing, and soccer can cause the iliopsoas tendon to rub against an uncovered or prominent anterior acetabular cup edge. An acetabular component that overhangs the anterior bony acetabular rim by >2 mm, or an uncontained anterior screw head, frequently produces chronic, disabling groin pain during active hip flexion.

Mitigation Strategy: Palpate and inspect the anterior acetabular wall intraoperatively. The anterior rim of the cup must remain flush or recessed within the anterior bony acetabular border. Avoid excessive cup retroversion or lateralization. If conservative measures (physical therapy, targeted corticosteroid injections) fail, arthroscopic or open iliopsoas tenotomy and cup revision may be required.

10. Special Populations: Young Athletes & Heavy Manual Laborers

The Young Athlete (Age Under 50 Years)

Young athletes presenting for total hip arthroplasty frequently suffer from secondary coxarthrosis stemming from femoroacetabular impingement (FAI), slipped capital femoral epiphysis (SCFE), developmental dysplasia of the hip (DDH), or avascular necrosis (AVN). These patients maintain high physical resilience, robust musculature, and elevated expectations for athletic performance over multiple decades.

Reconstruction in this cohort requires durable initial biological fixation. Highly porous titanium or tantalum acetabular shells with multi-hole options permit supplementary screw fixation, resisting high shear loads before definitive osseointegration occurs. Highly cross-linked polyethylene paired with ceramic heads represents the standard bearing combination. In young athletes exhibiting hypermobility, extensive soft tissue laxity, or extreme functional range requirements, dual-mobility articulations may be considered selectively, balancing dislocation resistance against potential long-term intra-prosthetic bearing wear.

Heavy Manual Laborers and Military Personnel

Patients engaged in heavy manual occupations—such as construction workers, agricultural laborers, firefighters, and active-duty military service members—subject their prosthetic reconstructions to sustained heavy axial loads, repeated lifting (>50 to 100 lbs), deep kneeling, and ground-vibration stresses. In the meta-analysis by Pasqualini et al., the overall return-to-work rate following primary THA was 85.2%, with a mean time to return of 2.5 to 4.2 months. However, workers performing heavy physical labor required an average of 4 to 6 months before safely resuming full duties, and approximately 15% required permanent workplace modifications.

Surgical management demands robust primary stability. Tapered wedge titanium stems or fully porous-coated cylindrical designs provide reliable metaphyseal and diaphyseal scratch-fit stability, accommodating heavy cyclic torsional loads. Counseling must focus on lifting mechanics: lifting close to the body’s center of gravity, avoiding heavy twisting under axial load, and avoiding repetitive deep squats with heavy barbells to protect the posterior hip capsule from athletic subluxation.

11. Digital Biomarkers & Continuous Activity Monitoring

The Shift from Episodic Clinic Visits to Continuous Phenotyping

Traditional postoperative surveillance relies on episodic clinical consultations conducted at annual or biennial intervals. These visits yield static radiographic snapshots and retrospective patient surveys that fail to capture day-to-day functional variation. The integration of consumer smartphones, connected smartwatches, and specialized medical sensor platforms enables continuous longitudinal monitoring of digital biomarkers in the patient’s native environment.

Key Digital Mobility Biomarkers

• Gait Asymmetry and Stance Phase Ratio: Wearable sensors measure stance-time and swing-time symmetry between the operative and non-operative lower extremities. Subtle increases in operative limb offloading often precede the clinical perception of pain by several weeks.
• Walking Velocity and Step Cadence: Continuous tracking of sustained walking bouts (>1 minute) measures functional walking velocity. Reductions in self-selected cadence correlate with progressive abductor fatigue, subclinical loosening, or contralateral joint degeneration.
• Active Energy Expenditure and MVPA Duration: Monitoring daily minutes spent in moderate-to-vigorous physical activity provides an objective measure of cardiovascular and musculoskeletal functional capacity.

Future Directions: Smart Implants and Remote Joint Monitoring

The next frontier in activity measurement is the integration of internal sensing technologies into prosthetic components. Smart tibial and femoral implants equipped with embedded micro-electromechanical systems (MEMS), low-power Bluetooth transceivers, and strain gauges have undergone initial clinical trials. These internally sensorized implants measure real-time in vivo forces, joint temperature, and interface micro-motion, alerting clinicians to abnormal load spikes, infection, or component loosening before irreversible bone loss occurs.

12. Master Class Pro-Tip

“When managing high-demand athletes and heavy manual laborers undergoing primary total hip arthroplasty, never rely on static pelvic radiographs alone to establish component orientation. Obtain standing and relaxed-seated lateral spinopelvic radiographs preoperatively to assess sagittal pelvic tilt and spinal flexibility. In athletes with stiff lumbar spines or prior spinal fusion, the pelvis fails to retrovert during seated postures and fails to antevert during standing extension, significantly elevating the risk of athletic impingement and late dislocation. Select a 36 mm ceramic head paired with a highly cross-linked polyethylene liner to optimize jump distance and maximize range of motion prior to neck-socket contact. Avoid femoral heads exceeding 36 mm in high-demand young patients, as the elevated frictional torque transmitted to the 12/14 trunnion taper promotes mechanically assisted crevice corrosion and trunnionosis. Reconstruct horizontal femoral offset anatomically using high-offset stem geometries rather than increasing neck length, tensioning the abductor complex without introducing iatrogenic limb lengthening.”

Master Class Surgical Pearl: High-Demand Arthroplasty Management

13. Evidence-Based Synthesis

Modern clinical decision-making is grounded in high-quality randomized controlled trials and prospective registry analyses, corroborated by seminal biomechanical and anatomical descriptions.

14. References

• Pasqualini I, Emara AK, Rullan PJ et al. Return to Sports and Return to Work After Total Hip Arthroplasty: A Systematic Review and Meta-analysis. JBJS Rev. 2023. doi:10.2106/JBJS.RVW.22.00249 [Level I: Systematic Review / Meta-Analysis]
• Talbot S, Hooper G, Stokes A et al. Use of a new high-activity arthroplasty score to assess function of young patients with total hip or knee arthroplasty. J Arthroplasty. 2010. doi:10.1016/j.arth.2008.09.019 [Level II: Prospective Validation Study]
• Zahiri CA, Schmalzried TP, Szuszczewicz ES et al. Assessing activity in joint replacement patients. J Arthroplasty. 1998. doi:10.1016/s0883-5403(98)90195-4 [Level II: Cross-Sectional Validation Cohort]
• Klein GR, Levine BR, Hozack WJ et al. Return to athletic activity after total hip arthroplasty. Consensus guidelines based on a survey of the Hip Society and American Association of Hip and Knee Surgeons. J Arthroplasty. 2007. doi:10.1016/j.arth.2006.09.001 [Level V: Consensus Expert Survey]
• Healy WL, Sharma S, Schwartz B et al. Athletic activity after total joint arthroplasty. J Bone Joint Surg Am. 2008. doi:10.2106/JBJS.H.00274 [Level V: Clinical Consensus Appraisal]
• Schmalzried TP, Szuszczewicz ES, Northfield MR et al. Quantitative assessment of walking activity after total hip or knee replacement. J Bone Joint Surg Am. 1998. doi:PMID:9469309 [Level II: Prospective Biomechanical Monitoring Cohort]
• Shiomoto K, Hamai S, Hara D et al. Objective Activity Levels and Patient-Reported Outcomes After Total Hip Arthroplasty and Periacetabular Osteotomy: Retrospective Matched Cohort Study at Mean 12-Year Follow-Up. J Arthroplasty. 2023. doi:10.1016/j.arth.2022.08.034 [Level III: Retrospective Matched Cohort Study]