MUA, arthroscopic lysis, or open arthrolysis | Advanced
- Stiff TKA defined as flexion less than 90° or flexion contracture greater than 10°
- MUA most effective at 6-12 weeks post-TKA - early is better
- Always exclude infection before any intervention for stiffness
- Address underlying cause: malposition, sizing, soft tissue imbalance
- “TIMING IS CRITICAL: earlier MUA gives roughly double the flexion gain - mean gain about 36° early vs about 17° late (after 12 weeks); delayed MUA carries higher complication and revision risk
- “EXCLUDE INFECTION: ESR, CRP, aspiration before any stiffness procedure
- “CAUSES OF STIFFNESS: Component malposition (especially femoral internal rotation), oversizing, infection, CRPS, patient compliance
- “FUNCTIONAL ROM: about 67° for swing phase, about 83° for stairs, about 93° for rising from chair, about 105° for tying shoes (Rowe gait analysis)
When & Why
Define the problem first. A stiff TKA is a working diagnosis: flexion less than 90° OR a flexion contracture greater than 10°. Kim and Lotke used stricter criteria (flexion under 75° and/or flexion contracture 15° or more) and reported a prevalence of 1.3 percent. The threshold matters because reported stiffness prevalence ranges from roughly 1 to 5 percent depending on the definition used — state your working definition in any exam answer, as there is no single international consensus. Why range of motion matters. Functional daily activities demand a defined arc of flexion, and a stiff knee robs the patient of independence even when the arthroplasty is otherwise sound:
- Level walking: about 67° of flexion
- Stair climbing: about 83°
- Rising from a chair: about 93°
- Tying shoes: about 105° Exclude infection before anything else. This is the non-negotiable first step for every stiff TKA — operating on an infected knee through a stiff scar converts a salvageable problem into a disaster. Screen with ESR (greater than 30mm/hr suspicious), CRP (greater than 10mg/L suspicious) and a knee aspiration (synovial WBC greater than 1,100 cells per microlitre or PMN greater than 64 percent). Add alpha-defensin if the markers are equivocal, and hold antibiotics for a two-week washout before aspirating. The one decision that matters. Once infection is excluded and the component position assessed, management is driven by TIMING and by whether the components are malpositioned. Choose the least invasive option that can succeed:
Early stiffness (less than 12 weeks) with sound components. Lowest morbidity and the biggest gain when done early — the first-line intervention.
Intermediate stiffness (3-6 months) or failed MUA, with sound components. Adhesion release through standard portals and faster recovery than open surgery.
Late stiffness (greater than 6 months) with mature scar, sound components. The definitive soft-tissue operation — comprehensive gutter and pouch release.
Any timing WITH component malposition (femoral internal rotation greater than 3°, oversizing, loosening). Address the mechanical cause — arthrolysis alone fails if the component is wrong.
- No component issue
- MUA
- Component issue
- MUA first, revise if it fails
- No component issue
- Arthroscopic or open lysis
- Component issue
- Revision with lysis
- No component issue
- Open arthrolysis
- Component issue
- Revision TKA
Consent specifically for periprosthetic fracture or extensor-mechanism rupture (especially with MUA), recurrent stiffness (10-20 percent), haemarthrosis, wound problems, infection, and the possibility that a malpositioned component found intraoperatively converts the plan to a revision. Setup. Supine on a standard operating table. MUA needs full muscle relaxation under general or spinal anaesthesia with the tourniquet available but NOT inflated. Arthrolysis needs a thigh tourniquet, a full revision instrument set with constrained liners and polyethylene exchange options on standby, and extensile-exposure instruments (a quadriceps snip, plus tibial tubercle osteotomy equipment for the severe case). Fluoroscopy should be available.
The Operation
The goal is to restore a functional arc — at least 110-120° of flexion with full extension — by removing the restrictive scar and correcting any mechanical cause, while protecting the extensor mechanism, the collateral ligaments and the popliteal neurovascular bundle. Three operations do this in order of escalating invasiveness: manipulation under anaesthesia (the early, low-morbidity option), arthroscopic lysis (the middle ground), and open arthrolysis (the definitive soft-tissue release, laid out below as the centerpiece). The exposure for open arthrolysis is the medial parapatellar approach with extensile escalation, described step by step in the sequence below.
Manipulation under anaesthesia (MUA) — the early, low-morbidity option
- Patient supine on a standard operating table. General anaesthesia or spinal with COMPLETE motor block is essential — any muscle guarding transmits force to bone and risks fracture.
- Tourniquet on the thigh but NOT inflated. Fluoroscopy available.
- Document the pre-manipulation range under anaesthesia and compare it with the intraoperative ROM recorded at the primary surgery.
- Note any crepitus, instability or malalignment before you begin.
- Targets: flexion greater than 120° (or within 10° of the primary intraoperative range) and full (0°) extension.
- One hand holds the distal femur providing counter-pressure; the other holds the PROXIMAL tibia.
- Apply slow, progressive flexion and feel for the sequential release of adhesions (a series of pops).
- Target a minimum of 120° flexion, or until audible and palpable scar release ceases.
- For a flexion contracture, extend the knee fully with gentle sustained pressure, holding for 60-90 seconds.
- Feel for release of the posterior capsule.
- If excessive force was needed or there was a sudden loss of resistance, obtain AP and lateral fluoroscopic images to exclude an occult periprosthetic fracture.
- Document the final ROM achieved, check for crepitus, instability or haemarthrosis, and apply a compression bandage.
- Proceed immediately to the post-MUA rehabilitation protocol (CPM, regional analgesia, aggressive physiotherapy).
MUA is most effective when performed early. The pooled evidence (Issa and Mont, JBJS 2014; Akhtar meta-analysis, 2024) shows the mean flexion gain is roughly double for early manipulation (within about 12 weeks) versus late — approximately 32-37° early versus 17-19° late — and Mont reported unsatisfactory outcomes for MUA performed beyond 26 weeks. Delayed MUA also carries significantly higher complication and revision rates. Beyond 3-6 months the scar matures and MUA becomes progressively less effective; move to open lysis.
NEVER use rapid, forceful manipulation — the risks are periprosthetic fracture and tendon rupture. Apply the force THROUGH THE TIBIA, not through the ankle (leverage through the ankle injures the ligaments). Maintain axial compression during flexion to reduce the fracture risk. If you meet resistance at 90° with no release, STOP and use fluoroscopy to exclude an occult fracture.
Periprosthetic fracture, component loosening, infection, heterotopic ossification (Brooker III/IV), greater than 6 months since surgery, and a previous extensor-mechanism repair.
Arthroscopic lysis — the middle ground. For intermediate stiffness (3-6 months) or a failed MUA with sound components, arthroscopic adhesolysis releases scar through standard knee arthroscopy portals. Use anterolateral and anteromedial portals with an arthroscopic shaver and radiofrequency device, adding superomedial or superolateral portals to reach the suprapatellar pouch. Divide adhesions in the suprapatellar pouch and gutters to restore quadriceps excursion and patellar mobility, taking care posteriorly where the capsule is thin. It shares the open-release principles below but avoids an arthrotomy, allowing faster rehabilitation.
Open arthrolysis — the definitive operation (exposure laid out as the first steps)
- Patient supine with a thigh tourniquet. Use the PREVIOUS midline incision.
- Raise full-thickness skin flaps to expose the fascia, incise the fascia and identify the arthrotomy plane.
- Begin a medial parapatellar arthrotomy. In a stiff knee the patella often will not evert — do NOT force it (see the extensile hierarchy in Step 2).
If the patella cannot be everted or subluxed after the standard medial parapatellar arthrotomy, escalate in this order:
- Quadriceps snip — a 45° incision from the proximal apex of the medial arthrotomy into the vastus lateralis tendon (about 3-4cm). Converts the arthrotomy to a lazy-S, letting the patella sublux laterally rather than evert. First-line: minimal morbidity and NO change to rehabilitation.
- Rectus snip — release the rectus femoris tendon from the quadriceps tendon proximally for a little more length; rarely needed.
- V-Y quadriceps turndown — a V-shaped quadriceps incision repaired in a Y, gaining 2-3cm. Reserved for severe cases; it DOES change rehabilitation — about 6 weeks in an extension brace with limited flexion.
- Tibial tubercle osteotomy (TTO) — last resort for stiffness surgery as it adds significant morbidity; 6-8 weeks of protected weight-bearing.
- The lateral gutter is the most common and most important site of restrictive adhesions.
- Use sharp dissection to release fibrotic tissue from the lateral femoral condyle, lateral tibial plateau and lateral patellar facet, and restore patellofemoral tracking.
- Release adhesions in the suprapatellar pouch — essential to restore quadriceps excursion. Blunt finger dissection is often sufficient; ensure the quadriceps glides freely.
- Release medial parapatellar adhesions, taking care around the MCL insertion on the femur and tibia. This is a less common site of restrictive adhesions than the lateral side.
For a flexion contracture greater than 10° that has not responded to the anterior releases:
- Flex the knee to 90° to carry the popliteal vessels posteriorly, away from the capsule.
- Use a curved elevator on the posterior tibia, releasing the posterior capsule while STAYING ON BONE.
- Re-check extension and repeat if needed.
Assess for component malposition that will otherwise guarantee recurrence:
- Femoral rotation — internal rotation causes lateral patellar tracking and stiffness.
- Femoral sizing — oversizing causes anterior impingement in flexion.
- Tibial rotation — should align with the tibial tubercle.
- Posterior osteophytes — remove any residual.
Consider an insert exchange if the thickness is contributing to overstuffing, if the bearing is damaged by manipulation or arthrofibrosis debris, or if the soft-tissue releases have created a need for increased constraint.
- Confirm greater than 120° flexion and full extension, and check patellar tracking (the no-thumb test).
- Close in layers over a drain and apply a compression bandage with the knee in extension.
The lateral gutter release must NOT extend below the joint line — the common peroneal nerve wraps the fibular neck about 2-3cm distal to the joint line and is closely applied to bone there. If distal extension is unavoidable, identify and protect the nerve at the fibular neck, avoid retractors at that level, and check foot dorsiflexion immediately post-operatively.
The popliteal artery lies just millimetres behind the posterior capsule, closest in full extension and tethered behind the joint at the level of the femoral condyles. Crucially, it falls further posteriorly (away from the capsule) as the knee flexes — which is exactly why the knee is flexed to 90° for any posterior release. For the posterior capsule release, ALWAYS flex the knee, use a curved elevator hugging the posterior tibia and stay on bone, and never use sharp dissection or blind diathermy posteriorly. Injury may not be immediately apparent (an intimal tear can thrombose later). If arterial bleeding occurs: apply direct pressure, extend the knee and call vascular surgery.
Choose the lateral parapatellar approach if you anticipate difficulty (it gives direct access to lateral gutter adhesions and easier patellar subluxation), and escalate through the quadriceps snip before ever forcing eversion. Forcing eversion in a stiff knee is how the patellar tendon avulses off the tubercle.
Aftercare & Complications
Rehabilitation protocol | Phase | Timing | Goals and intervention | |-------|--------|------------------------| | Immediate | Day 0-3 | Continuous Passive Motion (CPM) starting 0-90°, increasing 10° per day; regional anaesthesia via an indwelling femoral catheter or adductor canal block for 48-72 hours; cryotherapy and compression. Isometric quadriceps and ankle pumps from day 1. | | Early mobilisation | Day 2-3 to week 1 | Weight-bearing as tolerated, active ROM exercises. | | Week 1-2 | — | Target 90° flexion and full extension. | | Week 2-6 | — | Progress to full ROM and strengthening. | | Week 6-12 | — | Return to activities. | Adjunctive measures
- NSAIDs (indomethacin 25mg TDS) for heterotopic ossification prophylaxis.
- Consider low-dose radiation in patients at high risk of heterotopic ossification.
- Psychological support and early pain-team involvement if CRPS is suspected.
The ROM you achieve in theatre is lost unless the patient can rehabilitate aggressively and painlessly. Regional anaesthesia (a femoral catheter or adductor canal block) allows intensive early physiotherapy without the sedation and nausea that opioids bring — which is exactly what limits participation and lets the knee re-stiffen.
Complications
- Recognition
- Sudden loss of resistance during MUA, pain, inability to weight-bear
- Prevention
- Gentle progressive manipulation, axial compression during flexion, fluoroscopy if uncertain
- Management
- ORIF if the implant is stable, revision if loose — supracondylar femur is the most common site
- Recognition
- Loss of active extension, palpable gap, patella alta on the lateral radiograph
- Prevention
- Avoid MUA if patella baja is present, maintain 45° flexion during exposure, do not force patellar eversion
- Management
- Primary repair if acute (within 2 weeks); reconstruction with allograft if chronic
- Recognition
- Loss of active extension, palpable gap at the quadriceps tendon or patella
- Prevention
- Use extensile approaches (quadriceps snip) rather than forcing eversion; avoid MUA beyond 3 months
- Management
- Primary repair with augmentation, may need mesh reinforcement, protect for 6-8 weeks
- Recognition
- Progressive loss of ROM over weeks to months despite initial improvement
- Prevention
- Aggressive physiotherapy, maintain ROM with CPM for 2-3 weeks, address the underlying cause
- Management
- Repeat MUA if early recurrence; revision if there is a component issue; consider psychological assessment
- Recognition
- Swelling, pain, warmth, decreased ROM in the immediate postoperative period
- Prevention
- Meticulous haemostasis, drain placement, appropriate anticoagulation dosing
- Management
- Aspiration for a tense effusion; washout if recurrent; check for a coagulopathy
- Recognition
- Dehiscence, prolonged drainage, skin necrosis especially over the patella
- Prevention
- Handle tissues gently, raise full-thickness flaps, obtain adequate release before forcing closure
- Management
- VAC therapy, plastic surgery input for coverage, delay rehabilitation if the wound is compromised
- Recognition
- Persistent pain, swelling, elevated inflammatory markers, wound drainage
- Prevention
- Sterile technique, prophylactic antibiotics, avoid haematoma, optimise nutrition
- Management
- Aspiration; debridement and insert exchange if early; two-stage revision if chronic
- Recognition
- Burning pain out of proportion, allodynia, skin changes, stiffness despite adequate ROM under anaesthesia
- Prevention
- Early recognition and treatment pre-operatively, avoid prolonged tourniquet, regional anaesthesia
- Management
- Pain medicine involvement, mirror therapy, vitamin C prophylaxis (500mg daily)
- Recognition
- Foot drop, numbness of the lateral leg and dorsum of the foot post-operatively
- Prevention
- Avoid retractors at the fibular neck, protect the nerve during lateral release
- Management
- Observation for 3 months (most recover), AFO, nerve exploration if no recovery
- Recognition
- Valgus instability, may not be apparent until weight-bearing
- Prevention
- Protect the MCL during medial release, avoid valgus stress during manipulation
- Management
- Hinged brace for grade I/II, primary repair for grade III, may need a constrained revision TKA
Viva & Exam Focus
SPACESPACE — causes of post-TKA stiffness
LYSISLYSIS — open arthrolysis release sequence
Clinical Decision Scenarios
Practise clinical reasoning and management decisions out loud
“A 62-year-old woman is referred 8 weeks post-primary TKA with flexion of only 70°. She was discharged at 85° flexion on day 3. How would you assess and manage this patient?”
“During open arthrolysis for a stiff TKA, you cannot evert the patella after a standard medial parapatellar arthrotomy. What are your options and how do you decide which to use?”
“You see a 58-year-old man 6 months post-TKA with a flexion contracture of 15° and flexion of only 80°. His inflammatory markers are normal and aspiration was negative. CT shows 5° internal rotation of the femoral component. How do you manage this case?”
Definition and timing
- Stiff TKA (working definition): flexion less than 90° OR flexion contracture greater than 10° (Kim/Lotke used stricter flexion under 75° and/or FCE 15° or more)
- MUA window: earliest practical — flexion gain roughly doubles when done within about 12 weeks; outcomes unsatisfactory beyond 26 weeks
- Open lysis: 3-6 months or failed MUA
- Revision: greater than 6 months or component malposition
SPACE causes
- Sepsis — always exclude infection first (ESR, CRP, aspirate)
- Patient — pre-op stiffness (strongest predictor), CRPS, compliance
- Arthrofibrosis — excessive scar formation
- Component — malposition (greater than 3° IR), oversizing, instability
- Extensor mechanism — patella baja, maltracking
Critical numbers
- Functional ROM: 67° walking, 83° stairs, 93° chair, 105° shoes
- Femoral rotation: greater than 3° internal rotation equals malposition
- Insall-Salvati: 0.8-1.2 normal, less than 0.8 equals patella baja
- Infection thresholds: WBC greater than 1,100 per microlitre, PMN greater than 64%
MUA technique
- Complete muscle relaxation essential
- Counter-pressure on the femur, force through the tibia (not the ankle)
- Gentle progressive flexion, feel for adhesion release
- Target greater than 120° flexion, full extension
- STOP if resistance without release at 90° — check for fracture
LYSIS release sequence
- Lateral gutter first (most common adhesions)
- Suprapatellar pouch (restore quadriceps excursion)
- Medial gutter
- Posterior capsule (for FCE only — knee flexed to 90°)
Extensile exposure hierarchy
- 1. Quadriceps snip — first line, no rehab change
- 2. Rectus snip — additional length if needed
- 3. V-Y turndown — needs 6 weeks in an extension brace
- 4. TTO — last resort, 6-8 weeks protected weight-bearing
Danger structures
- Popliteal artery — immediately behind the capsule (closest in extension); flex the knee to 90° for posterior release
- Common peroneal nerve — protect at the fibular neck during lateral release
- Patellar tendon — risk of avulsion during MUA; maintain 45° flexion during exposure
- Extensor mechanism — avoid forced eversion
- MCL — protect during medial release
Post-operative protocol
- CPM from day 0, increase 10° per day
- Regional anaesthesia for 48-72 hours (femoral catheter or adductor canal block)
- Aggressive physiotherapy
- NSAIDs for HO prophylaxis (indomethacin 25mg TDS)
Background & Evidence
Epidemiology. Reported prevalence of clinically significant stiffness varies widely (roughly 1-5 percent) depending on the threshold used. Kim and Lotke (flexion contracture 15° or more and/or flexion under 75°) found 1.3 percent; series using flexion under 90° report higher rates. There is no single international consensus definition — state your working definition in any exam answer. Why a knee stiffens — the SPACE causes in full. Stiffness is the final common pathway of several distinct mechanisms, grouped by the SPACE mnemonic:
- Specific causes
- Pre-operative stiffness (the STRONGEST predictor of outcome); Complex Regional Pain Syndrome; poor compliance with physiotherapy; low pain tolerance; diabetes and inflammatory arthritis
- Specific causes
- Component malposition (especially femoral internal rotation greater than 3°); femoral oversizing (blocks flexion); tibial oversizing or malposition; patella baja or maltracking; inadequate posterior osteophyte removal; residual PCL in a PS design
- Specific causes
- Infection (must exclude in all cases); haematoma or haemarthrosis; prolonged immobilisation; inadequate analgesia limiting rehabilitation; heterotopic ossification
- Specific causes
- Excessive, disorganised scar formation — the idiopathic soft-tissue cause once infection and component issues are excluded
Where the scar forms. Restrictive adhesions have favourite sites, and the release priority follows where they cause the most restriction:
- Effect on ROM
- Limits flexion
- Release priority
- High
- Effect on ROM
- Limits flexion and patellar mobility
- Release priority
- Highest
- Effect on ROM
- Limits flexion
- Release priority
- Moderate
- Effect on ROM
- Limits extension
- Release priority
- For flexion contracture only
- Effect on ROM
- Limits flexion
- Release priority
- Moderate
Temporal classification. The timing of presentation dictates the intervention:
- Definition
- Less than 6-12 weeks
- Preferred treatment
- MUA (optimal window)
- Definition
- 3-6 months
- Preferred treatment
- Arthroscopic or open lysis
- Definition
- Greater than 6 months
- Preferred treatment
- Open arthrolysis plus or minus revision
Pre-operative component assessment. Before any intervention, image the components to find a correctable mechanical cause:
- AP and lateral radiographs — component position, sizing and loosening.
- Skyline view — patellar tracking, thickness and position.
- CT rotation study — femoral component rotation (should be 0-3° external relative to the transepicondylar axis; greater than 3° internal rotation equals malposition).
- Component detail — posterior condylar offset and joint-line height; tibial rotation should align with the tibial tubercle; patella baja (Insall-Salvati less than 0.8) limits flexion and alta limits stability; a femoral component oversized in the AP dimension causes anterior impingement in flexion. Key evidence — timing is the single most modifiable factor. The consistent message across the pooled literature is that earlier intervention yields larger gains and fewer complications. Issa and Mont (JBJS 2014) showed early MUA (within 12 weeks) gave a mean flexion gain of 36.5° versus 17° for late MUA, with higher final ROM and Knee Society scores; manipulations after 26 weeks produced unsatisfactory outcomes. Akhtar's 2024 meta-analysis of 14 studies and 13,445 knees confirmed the mean flexion gain nearly doubled with early MUA (32.0° versus 19.2°), and that delayed MUA carried significantly higher complication and revision risk. Ghani's 2012 systematic review compared the four modalities and found mean ROM gains of MUA plus 38.4°, arthroscopic release plus 36.2°, open release plus 43.4° and revision TKA plus 24.7°, with no significant difference in Knee Society Score between them. Guidelines, Registries and Global Practice. AAOS (US), BOA and British arthroplasty practice, and EFORT-aligned European centres all favour early MUA when supervised physiotherapy fails to restore functional flexion, reflecting the consistent timing data; the trend across systematic reviews is to manipulate earlier rather than adhere rigidly to an arbitrary 3-month cut-off, because gains taper progressively rather than disappearing abruptly. National arthroplasty registries (NJR England and Wales, AJRR USA, AOANJRR Australia, SHAR Sweden, NZJR New Zealand) capture revision for stiffness or arthrofibrosis as a revision indication, but most code MUA separately or not at all — so registry rates underestimate the true stiffness burden. Use registry data for revision-for-stiffness signals, not for MUA incidence.
References
Management of stiffness following total knee arthroplasty: a systematic review
- Systematic review of 25 studies (798 patients) comparing the four main treatments for post-TKA arthrofibrosis
- Mean ROM gain: MUA plus 38.4°, arthroscopic release plus 36.2°, open surgical release plus 43.4°, revision TKA plus 24.7°
- No significant difference in Knee Society Score between the four modalities
- Evidence quality limited — most studies were retrospective case series (Newcastle-Ottawa 77/125)
The effect of timing of manipulation under anesthesia to improve range of motion and functional outcomes following total knee arthroplasty
- 144 manipulations reviewed; early MUA defined as within 12 weeks of TKA
- Early MUA gave greater mean flexion gain (36.5° vs 17°) and higher final ROM (119° vs 95°) than late MUA
- Early MUA gave higher Knee Society objective (89 vs 84) and function (88 vs 83) scores
- Manipulations performed after 26 weeks produced unsatisfactory clinical outcomes
Outcomes of Early Versus Delayed Manipulation Under Anesthesia for Stiffness Following Total Knee Arthroplasty: A Systematic Review and Meta-Analysis
- 14 studies, 13,445 knees; about 72% early MUA, about 28% delayed MUA (early most often defined as within 3 months)
- Mean flexion gain nearly doubled in the early group (32.0° vs 19.2°)
- Post-MUA flexion was similar between groups, but pre-MUA flexion was higher in the delayed group
- Delayed MUA carried significantly higher risk of surgical and medical complications and of subsequent revision TKA
Risk Factors, Outcomes, and Timing of Manipulation Under Anesthesia After Total Knee Arthroplasty
- 62 of 1729 primary TKAs required MUA (about 3.6%)
- MUA patients were younger (55 vs 65 years), more often current smokers and more likely to have had prior knee surgery (commonly arthroscopy)
- Final flexion after MUA within 6 weeks (106.7°) was equivalent to matched controls (115.6°), whereas late MUA after 6 weeks was not (101.3°)
- Pre-TKA flexion did not differ between groups — the stiffness was post-operative, not pre-existing
Stiffness after total knee arthroplasty. Prevalence of the complication and outcomes of revision
- Stiffness defined as flexion contracture 15° or more and/or flexion under 75°; prevalence 1.3% in 1000 primary TKAs
- Patients who became stiff had significantly less pre-operative extension and flexion
- After revision for stiffness, mean flexion improved 65.8° to 85.4° and arc of motion improved in 93% of knees
- Authors concluded the benefits of revision for stiffness are real but modest
Further reading 1. Pfefferle KJ, Shemory ST, Tilbury RT, et al. Risk factors for manipulation after total knee arthroplasty: a pooled electronic health record database study. J Arthroplasty. 2014;29(10):2036-2038. 2. Scranton PE Jr. Management of knee pain and stiffness after total knee arthroplasty. J Arthroplasty. 2001;16(4):428-435. 3. Christensen CP, Crawford JJ, Olin MD, Vail TP. Revision of the stiff total knee arthroplasty. J Arthroplasty. 2002;17(4):409-415. 4. Nicholls DW, Dorr LD. Revision surgery for stiff total knee arthroplasty. J Arthroplasty. 1990;5(Suppl):S73-77. 5. Esler CN, Lock K, Harper WM, Gregg PJ. Manipulation of total knee replacements. Is the flexion gained retained? J Bone Joint Surg Br. 1999;81(1):27-29. 6. Kim J, Nelson CL, Lotke PA. Stiffness after total knee arthroplasty: prevalence of the complication and outcomes of revision. J Bone Joint Surg Am. 2004;86(7):1479-1484. 7. Yercan HS, Sugun TS, Bussiere C, et al. Stiffness after total knee arthroplasty: prevalence, management and outcomes. Knee. 2006;13(2):111-117. 8. Ghani H, Maffulli N, Khanduja V. Management of stiffness following total knee arthroplasty: a systematic review. Knee. 2012;19(6):751-759. 9. Mont MA, Serna FK, Krackow KA, Hungerford DS. Exploration of radiographically normal total knee replacements for unexplained pain. Clin Orthop Relat Res. 1996;331:216-220. 10. Issa K, Banerjee S, Kester MA, et al. The effect of timing of manipulation under anesthesia to improve range of motion and functional outcomes following total knee arthroplasty. J Bone Joint Surg Am. 2014;96(16):1349-1357. 11. Newman ET, Herschmiller TA, Attarian DE, et al. Risk factors, outcomes, and timing of manipulation under anesthesia after total knee arthroplasty. J Arthroplasty. 2018;33(1):245-249. 12. Akhtar M, Razick D, Seibel A, et al. Outcomes of early versus delayed manipulation under anesthesia for stiffness following total knee arthroplasty: a systematic review and meta-analysis. J Arthroplasty. 2024;39(11):2872-2879.