High-yield overview
Allograft | Post-Meniscectomy Pain | Joint Preservation
AllograftDonor meniscus
less than 50 yrIdeal patient age
SizingCritical for success
PainRelief primary goal
Indications
Post-Meniscectomy
PatternSymptomatic compartment
TreatmentPain with activity
Young Patient
PatternTypically under 50
TreatmentJoint preservation
Normal Alignment
PatternOr correct with HTO
TreatmentCritical for success
Critical Must-Knows
- Post-meniscectomy pain in young patient is primary indication
- Graft sizing is critical (plain X-ray or MRI)
- Normal alignment required (or correct with HTO)
- Kellgren-Lawrence grade 2 or less (significant OA = poor results)
- Bone plug or bridge technique for root fixation
Clinical Pearls
- "Fresh-frozen allograft most common
- "Size match within 5% of native meniscus
- "May combine with HTO, ACL recon, cartilage procedures
- "Goals: Pain relief, delay arthroplasty
Critical Meniscal Transplant Exam Points
Indications
Post-meniscectomy syndrome: Pain in meniscectomized compartment. Young (under 50 ideally). Minimal arthritis (KL grade 2 or less). Normal or corrected alignment.
Contraindications
Advanced OA (KL 3-4). Uncorrected malalignment. Inflammatory arthritis. Knee instability (unless addressed). Obesity (relative).
Sizing
Critical for success. Size from AP and lateral X-rays or MRI of contralateral knee. Match within 5% of native dimensions. Pollard method common.
Technique
Bone plug or bone bridge for root fixation (better healing than soft tissue). Arthroscopic or mini-open. Suture periphery to capsule. Protect weight-bearing 4-6 weeks.
Mnemonic
YAPSMAT Candidacy
| Y | Young (under 50) Joint preservation goal |
| A | Alignment normal Or correct with HTO |
| P | Post-meniscectomy pain Primary indication |
| S | Small arthritis (KL 2 or less) Advanced OA = poor results |
| Y | Young (under 50) Joint preservation goal | P | Post-meniscectomy pain Primary indication |
| A | Alignment normal Or correct with HTO | S | Small arthritis (KL 2 or less) Advanced OA = poor results |
Hook:YAPS = Young, Aligned, Post-meniscectomy, Small arthritis!
Mnemonic
OINKMAT Contraindications
| O | Obesity (BMI greater than 30) Mechanical overload, poor outcomes |
| I | Instability (ACL deficient) Must reconstruct ACL first |
| N | Not aligned (malalignment) Must combine with osteotomy |
| K | KL 3-4 arthritis Advanced OA = absolute contraindication |
| O | Obesity (BMI greater than 30) Mechanical overload, poor outcomes | N | Not aligned (malalignment) Must combine with osteotomy |
| I | Instability (ACL deficient) Must reconstruct ACL first | K | KL 3-4 arthritis Advanced OA = absolute contraindication |
Hook:OINK = Obese, Instability, Not aligned, KL advanced!
Mnemonic
5% RULEMAT Graft Sizing
| 5 | 5% size matching Graft must match within 5% of native |
| % | Pollard method AP/lateral radiographs, reliable sizing |
| R | Radiographs (AP/lateral) Measure tibial plateau width |
| U | Use contralateral MRI Alternative if native meniscus intact |
| L | Length and width both measured Two dimensions for accurate match |
| E | Error causes extrusion Oversizing leads to graft failure |
| 5 | 5% size matching Graft must match within 5% of native | R | Radiographs (AP/lateral) Measure tibial plateau width | L | Length and width both measured Two dimensions for accurate match |
| % | Pollard method AP/lateral radiographs, reliable sizing | U | Use contralateral MRI Alternative if native meniscus intact | E | Error causes extrusion Oversizing leads to graft failure |
Hook:5% RULE - accurate sizing prevents extrusion!
Overview and Indications
Meniscal allograft transplantation (MAT) replaces a previously resected meniscus with a size-matched donor allograft. The goal is pain relief and delay of arthritis progression and eventual arthroplasty.
Ideal Candidate
- Young (typically under 50 years)
- Post-total or near-total meniscectomy
- Symptomatic compartment pain
- Minimal arthritis (Kellgren-Lawrence grade 2 or less)
- Normal alignment (or willing to correct with osteotomy)
- Stable knee (ACL intact or reconstructed)
- Reasonable BMI
Goals
- Pain relief (primary)
- Improved function
- Delay of arthritis progression
- Delay of arthroplasty
Pathophysiology of the Meniscus-Deficient Knee
The meniscus transmits 50-70% of axial load in the compartment, deepens the tibial articular surface, and contributes to shock absorption, joint lubrication and secondary stability. Total meniscectomy removes this protection, and the rationale for MAT is to restore that biomechanical role.
Why Meniscectomy Damages the Joint
- Contact area falls and peak contact stress rises sharply — after total meniscectomy contact pressure can rise by roughly two-to-three-fold, concentrating load on a smaller cartilage footprint.
- Accelerated cartilage wear — the classic basis of the Fairbank changes (joint space narrowing, ridge/osteophyte formation, flattening of the femoral condyle) seen radiographically after meniscectomy.
- Lateral compartment is least forgiving — the lateral compartment is more conforming and more meniscus-dependent, so lateral meniscectomy is poorly tolerated and lateral compartment OA can progress rapidly.
Post-Meniscectomy Syndrome
This is the target clinical entity for MAT: activity-related pain localised to the meniscectomised compartment in a knee that is still relatively well preserved (cartilage largely intact, alignment neutral, ligaments competent). The graft restores load distribution; it does not regenerate cartilage that is already lost.
Clinical Presentation and Assessment
History
- Previous total or subtotal meniscectomy (often years earlier)
- Compartment-specific pain with activity, sport, prolonged standing or stairs
- Swelling after activity; sometimes mechanical symptoms
- Document prior ACL injury/reconstruction and any prior cartilage procedure
Examination
- Joint-line tenderness in the affected compartment
- Effusion; assess range of motion (stiffness is a relative contraindication)
- Ligament examination — Lachman/pivot-shift; instability must be corrected first
- Gait and alignment — varus or valgus thrust signals malalignment that must be addressed
Pre-operative Checklist (the four pillars)
- Cartilage — must be acceptable (Outerbridge/ICRS low grade; KL grade 2 or less)
- Alignment — neutral, or planned osteotomy to correct
- Stability — ligaments competent or reconstructed
- Sizing — accurate size-matched graft secured
Graft and Sizing
Graft Types
Fresh-Frozen Allograft: Most common. Stored at -70°C. Maintains mechanical properties. No viable cells.
Cryopreserved: Some cell viability preserved. More expensive. Uncertain clinical advantage.
Fresh: Highest cell viability. Logistical challenges. Disease transmission risk.
Sizing
Critical for success. Undersized or oversized grafts have inferior outcomes.
Methods:
- Plain radiographs of recipient knee (AP and lateral). Pollard method calculates meniscal dimensions from tibial plateau size.
- MRI of contralateral knee (if meniscus intact).
Match within 5% of native dimensions (width, length, horn-to-horn).
Investigations
Imaging Work-up
| Investigation | Purpose | Key point |
|---|---|---|
| Weight-bearing AP / Rosenberg (45° flexion PA) | Joint space, KL grade | Cartilage status drives candidacy; KL 3-4 contraindicated |
| Lateral and skyline views | Patellofemoral and tibial plateau dimensions | Used for Pollard sizing |
| Full-length standing (hip-knee-ankle) alignment | Mechanical axis | Mandatory — varus/valgus must be corrected before/with MAT |
| MRI | Cartilage grade, ligament integrity, contralateral meniscus sizing | Detects subchondral oedema and occult chondral loss |
| Sizing imaging | Pollard radiographic method or contralateral MRI/3D modelling | Oversizing causes extrusion; 3D MRI most accurate |
Sizing Methods Compared
- Pollard radiographic method — widely used; estimates dimensions from tibial plateau width and height on AP/lateral films. Reproducible but prone to outliers.
- Contralateral MRI / 3D surface modelling — uses the intact opposite meniscus as a template; reduces sizing outliers compared with radiographs.
- Intentional slight downsizing — reducing the radiographic estimate by about 5% lowers post-operative extrusion without harming clinical scores.
III
Beeler et al — 3D meniscus allograft sizing (280 healthy menisci)
Key Findings:
- 3D MRI sizing using the contralateral meniscus was superior for all parameters
- Outliers reduced by up to 55% versus 2D MRI and 83% versus Pollard radiographs for the medial meniscus
- Conventional radiographic (Pollard) sizing was the least accurate method
- Authors suggest radiographic sizing should probably not be recommended
Clinical Implication: Accurate sizing is critical; contralateral MRI/3D templating outperforms plain radiographs and reduces extrusion risk.
Source: J Orthop Surg Res 2020
III
Jang et al — modified Pollard (downsizing) and extrusion
Key Findings:
- 36 MAT patients: conventional Pollard sizing versus 5% downsized grafts
- Mean relative percentage of meniscal extrusion was lower in the downsized group (p = 0.037)
- Lysholm scores improved in all patients with no significant between-group difference
- No adverse clinical or radiographic effect from downsizing
Clinical Implication: Reducing graft size by ~5% from the Pollard estimate decreases extrusion without compromising clinical outcome.
Source: Arthroscopy 2011
Management: Surgical Technique
Bone Plug Technique: Each meniscal horn attached to a bone plug. Bone plugs inserted into bone tunnels in tibia. Bone-to-bone healing.
Bone Bridge Technique: Anterior and posterior horns connected by a strip of tibial bone. Slot created in tibial plateau to accept bridge.
Advantages: Better root fixation. More anatomic. Better load transmission.
Post-Operative and Outcomes
Rehabilitation
- Non-weight bearing or partial 4-6 weeks
- ROM early but protect flexion (limited to 90° initially)
- No deep squatting, pivoting for 4-6 months
- Progressive strengthening
- Return to sport 9-12 months (if permitted)
Outcomes
- Pain relief and functional improvement in the majority — reliable symptomatic benefit is the strongest evidence-based outcome
- Graft survival roughly 70-85% at 5 years, declining to ~45-75% at 10 years depending on definition of failure (clinical/reoperation versus strict MRI/radiographic criteria)
- Lateral MAT tends to fare better than medial in several series
- Chondroprotection is not proven — MAT may slow but does not reliably prevent OA progression
- Return to sport is variable and often not at the pre-injury level
Complications
| Complication | Notes |
|---|---|
| Graft extrusion | Common (≈15-20% of cases); radial subluxation over 3mm beyond the tibial margin reduces load-sharing. Driven by oversizing, malalignment and non-anatomic root position. Mild extrusion may not alter clinical results. |
| Graft tear / failure | Partial tears are the most frequent reoperation; failure defined as graft removal, revision or conversion to arthroplasty. |
| Arthrofibrosis / stiffness | More likely with combined procedures (osteotomy, ligament reconstruction, cartilage repair). |
| Incomplete healing of horns/periphery | Root or peripheral non-integration leads to loss of hoop-stress function. |
| Progression of OA | Continues in many despite a functioning graft. |
| Infection, neurovascular injury, DVT | General arthroscopic/open knee surgery risks; saphenous nerve and popliteal structures at risk with inside-out sutures. |
Differential Diagnosis of Post-Meniscectomy Knee Pain
Pain after meniscectomy has several causes; distinguishing them determines whether MAT is appropriate.
Causes of Pain in the Meniscectomised Knee
| 0 | 1 | 2 | 3 |
|---|---|---|---|
| Post-meniscectomy syndrome | Compartment-specific load pain, well-preserved joint | KL ≤2, intact cartilage on MRI | Ideal MAT indication |
| Established compartment OA | Constant pain, stiffness, deformity | KL 3-4, bone-on-bone | MAT contraindicated; consider osteotomy/arthroplasty |
| Malalignment overload | Varus/valgus thrust, compartment pain | Abnormal mechanical axis on long films | Must correct (osteotomy) before/with MAT |
| Chondral / osteochondral lesion | Catching, focal pain, effusion | ICRS lesion, subchondral oedema on MRI | May need concurrent cartilage procedure |
| ACL/ligament instability | Giving way, pivot symptoms | Positive Lachman/pivot, MRI ligament tear | Reconstruct first; instability dooms graft |
| Referred / extra-articular pain | Hip or spine pathology, non-mechanical | Normal knee imaging | MAT not indicated |
Controversies and Areas of Uncertainty
- Chondroprotection — the central unresolved question. Despite biomechanical plausibility, high-level evidence that MAT prevents OA progression is lacking; benefit on imaging endpoints is inconsistent.
- Cost-effectiveness — symptomatic and quality-of-life gains make MAT likely cost-effective, but this cannot be proven on current data because there is essentially no randomised comparison with non-surgical care.
- Fixation technique — bone plug/bridge versus soft-tissue suture-only fixation: registry/systematic-review data show good outcomes with both, and a clear superiority of bone fixation has not been definitively established.
- Graft processing — fresh-frozen non-irradiated grafts are most widely supported; the clinical advantage of cryopreserved or fresh viable grafts is uncertain, and irradiation/high-dose sterilisation may weaken the graft.
- Extrusion significance — extrusion is common but its correlation with symptoms and chondroprotection is debated; some extrusion appears clinically tolerated.
- Indication creep — expansion to older patients, higher chondral grades, and concomitant cartilage/osteotomy procedures outpaces the supporting evidence.
- Sizing standard — Pollard radiographs remain common despite evidence that contralateral MRI/3D modelling is more accurate.
Evidence Base
IV
Novaretti, Musahl et al — long-term survival (systematic review, min 10-year follow-up)
Key Findings:
- 11 studies, 658 patients, 688 MATs (mean age 33 years, 63% male)
- Mean survivorship 73.5% at 10 years and 60.3% at 15 years
- Functional scores (Lysholm, IKDC, KOOS, Tegner) improved versus pre-operative
- Most common complications: partial meniscal tears 11.1%, arthrofibrosis 3.6%, infection 2.0%
Clinical Implication: MAT yields good long-term survivorship and durable functional gains, but reoperation is common and benefit declines with time.
Source: Arthroscopy 2019
IV
Noyes & Barber-Westin — prospective long-term survivorship (worst-case analysis)
Key Findings:
- 72 consecutive bone-meniscus-bone transplants, 96% follow-up, mean 11.9 years
- Using strict endpoints (reoperation, MRI failure, extrusion over 50%, joint-space loss): survival 85% at 2y, 69% at 7y, 45% at 10y, 19% at 15y
- Significant improvement in pain, swelling, walking and stair climbing
- Cartilage damage, age and compartment did not significantly affect survival in this cohort
Clinical Implication: When stringent imaging criteria are applied, grafts undergo deleterious remodeling and often fail long-term — counsel that MAT is not curative.
Source: Am J Sports Med 2016
IV
Grassi, Zaffagnini et al — fresh-frozen MAT with soft-tissue fixation (min 10-year)
Key Findings:
- 46 patients, arthroscopic fresh-frozen MAT with soft-tissue (suture) fixation
- Survival free from surgical failure 91% at 5y and 86% at 10y
- Lateral MAT survival (73%) lower than medial MAT (96%)
- Tegner and KOOS-Sport declined from mid- to long-term; other scores stable
Clinical Implication: Soft-tissue-fixation fresh-frozen MAT can survive to 10 years; lateral grafts and sport-specific function are the weak points.
Source: Am J Sports Med 2020
IV
Waugh, Spalding et al — clinical and cost-effectiveness (systematic review)
Key Findings:
- Considerable observational evidence of symptom improvement after MAT
- Only one small pilot randomised comparison with non-surgical care exists
- MAT has not yet been proven to be chondroprotective
- Likely cost-effective via symptom relief and delayed arthroplasty, but cannot be proven on current data
Clinical Implication: Symptomatic benefit is well supported; chondroprotection and cost-effectiveness remain unproven for want of controlled trials.
Source: Knee Surg Sports Traumatol Arthrosc 2019
V
Figueroa et al — indications, techniques and outcomes (review)
Key Findings:
- MAT remains reserved for symptomatic meniscal loss in the well-preserved knee
- Lateral MAT has better clinical outcomes and lower failure risk than medial
- Mid-term survivorship 85-90%, falling to 50-70% long-term depending on chondral status
- Extrusion is common and does not clearly alter results; return to sport is uncertain
Clinical Implication: Best outcomes come from low chondral grade and lateral compartment; counsel realistically about sport and long-term durability.
Source: EFORT Open Rev 2019
Decision Algorithm
Algorithm
Exam Viva Scenarios
Use these scenarios to practise clinical reasoning and management decisions
CLINICAL SCENARIOStandard
Scenario 1: Post-Meniscectomy Pain
CLINICAL PROMPT
"A 35-year-old woman has medial compartment pain 5 years after total medial meniscectomy. X-rays show Kellgren-Lawrence grade 1 OA. How do you manage her?"
PRACTICAL APPROACH
This young patient with post-meniscectomy syndrome is an excellent candidate for meniscal allograft transplantation (MAT). She has symptomatic medial compartment pain following total meniscectomy, is young (35), and has minimal arthritis (KL grade 1) - all ideal criteria. Before proceeding, I would assess alignment on full-length standing X-rays. If she has significant varus malalignment, I would consider combining MAT with high tibial osteotomy to correct alignment and protect the transplant. I would confirm ACL integrity (stable knee required). For graft sizing, I would use AP and lateral radiographs with the Pollard method, or MRI of the contralateral knee if the meniscus is intact there. The graft should match within 5% of native dimensions. I prefer a fresh-frozen allograft with bone plugs or bone bridge technique for root fixation as this provides bone-to-bone healing and better load transmission than soft tissue fixation alone. Surgically, I would prepare the meniscal bed arthroscopically, create bone tunnels, pass the graft, secure the bone plugs, and suture the periphery to the capsule using inside-out technique. Post-operatively, she would be partial weight-bearing for 4-6 weeks, ROM limited initially, then progressive rehabilitation. Expected outcomes include pain relief in 70-80% and potential delay of arthroplasty. I would counsel that this does not prevent arthritis but may slow progression.
KEY CLINICAL POINTS
Ideal candidate: young, post-meniscectomy, minimal OA
Sizing is critical (within 5%)
Bone plug/bridge technique preferred
May combine with HTO if malaligned
COMMON PITFALLS
Not assessing alignment
Not knowing sizing methods
Performing in advanced OA
FURTHER QUESTIONS
"What are the contraindications?"
"What graft type do you use?"
CLINICAL SCENARIOChallenging
Scenario 2: Borderline Candidate with Malalignment - Combining MAT with HTO
CLINICAL PROMPT
"A 48-year-old keen amateur cyclist presents with progressive medial compartment knee pain over the past 2 years. He had a total medial meniscectomy 8 years ago following a traumatic bucket handle tear that was deemed irreparable at the time. His pain is now limiting his cycling and he has difficulty with stairs and prolonged standing. On examination, he has medial joint line tenderness, a small effusion, and mild varus thrust during gait. His range of motion is 0-130°. You obtain plain radiographs which show Kellgren-Lawrence grade 2 osteoarthritis in the medial compartment with some joint space narrowing and early osteophyte formation. Full-length standing alignment films show 5° of mechanical varus (mechanical axis passing medial to the knee center, loading the medial compartment). His BMI is 29. He has read about meniscal transplantation online and asks if he is a candidate. He is very motivated and wants to avoid knee replacement for as long as possible. How do you counsel him and what is your management plan if you proceed with surgery?"
PRACTICAL APPROACH
This patient represents a borderline candidate for meniscal allograft transplantation with several concerning features that require careful discussion. On the positive side, he is relatively young (48, though approaching the upper age limit of 50 typically quoted), has post-meniscectomy syndrome with compartment pain, maintains good range of motion (0-130°), has a stable knee (no mention of ligamentous instability), and has appropriate expectations (joint preservation, delay arthroplasty). However, several factors predict suboptimal outcomes: (1) KL grade 2 arthritis (the upper limit - KL 3-4 are contraindications), (2) 5° varus malalignment (will overload the transplanted meniscus and cause early failure if not corrected), (3) borderline age (48), and (4) borderline BMI (29). I would counsel him that he is a marginal candidate but that surgery could be considered with realistic expectations. The critical point is that meniscal transplantation alone will fail in the setting of varus malalignment - the mechanical overload will cause graft extrusion, degeneration, and failure. Therefore, if we proceed, we must combine MAT with high tibial osteotomy (HTO) to correct the varus and unload the medial compartment. This is a more extensive surgery than MAT alone, with higher risks and longer recovery. I would explain the combined procedure: First, perform closing wedge or opening wedge HTO to achieve slight valgus overcorrection (typically 3-5° valgus, mechanical axis passing through 60-65% of tibial width from medial, Fujisawa point), then perform MAT in the unloaded medial compartment. This can be done in a single-stage surgery (my preference if the patient is fit and motivated, though slightly higher stiffness risk) or staged with HTO first and MAT 6-12 months later after bone healing and alignment is confirmed. For graft sizing, I would use the Pollard method on AP and lateral radiographs of his knee, or MRI of the contralateral knee if the meniscus is intact, to match within 5% of his native dimensions. I would use a fresh-frozen medial meniscal allograft with bone bridge technique for secure root fixation. Post-operatively, rehabilitation would be prolonged due to the combined procedure - non-weight bearing for 6 weeks (HTO bone healing), then progressive weight-bearing, ROM initially limited to protect both the osteotomy and the meniscal transplant, with full return to activities at 12-18 months (longer than MAT alone). Expected outcomes: 70-80% achieve pain relief with MAT alone in ideal candidates, but his outcomes may be slightly worse given borderline indications (grade 2 OA). The HTO improves his prognosis by unloading the compartment. Realistic goal is pain reduction and delay of arthroplasty by 5-10 years, not cure. Alternative is to manage conservatively (activity modification, weight loss if BMI reduced, physiotherapy, analgesia) and accept that he will likely progress to knee replacement in 5-10 years anyway. Given his age (48) and motivation, combined MAT + HTO is reasonable but he must understand the risks, prolonged recovery, and uncertain long-term results.
KEY CLINICAL POINTS
Borderline MAT candidate - multiple concerning features requiring careful patient selection: Age 48 (approaching upper limit typically 50, though not absolute contraindication), KL grade 2 OA (upper acceptable limit - grade 3-4 contraindications), varus malalignment 5° (must correct or graft will fail), borderline BMI 29 (obesity relative contraindication); Positive features: post-meniscectomy pain (classic indication), good ROM, stable knee, motivated patient with appropriate goals (delay arthroplasty); Must weigh risks vs benefits - marginal candidate with realistic expectations may still benefit
Varus malalignment is ABSOLUTE contraindication unless corrected - uncorrected malalignment causes rapid MAT failure: Varus deformity overloads medial compartment (mechanical axis medial to knee center), causes graft extrusion, accelerated degeneration, and failure within 2-3 years; MAT alone in malaligned knee = guaranteed failure; Must combine MAT with HTO to correct alignment and unload compartment - this is fundamental principle of joint preservation surgery; Target alignment: slight valgus overcorrection (3-5° valgus, mechanical axis 60-65% tibial width from medial, Fujisawa point) to shift load to lateral compartment and protect medial MAT
Combined MAT + HTO surgical planning - single-stage vs staged approach: Single-stage (my preference): perform HTO first (opening or closing wedge), then MAT in same surgery; Advantages: single anesthetic, patient convenience, immediate alignment correction before MAT insertion; Disadvantages: longer operative time, slightly higher stiffness risk (10-15% vs 5-8% MAT alone), more complex rehabilitation; Staged approach: HTO first, confirm healing and alignment at 6-12 months, then MAT; Advantages: ensures alignment correction achieved, allows assessment of pain relief from HTO alone (may not need MAT), simpler individual surgeries; Disadvantages: two operations, prolonged overall recovery; Patient factors guide decision (age, fitness, motivation)
Realistic outcome expectations for borderline candidate - critical counseling points: Ideal MAT candidates (young, minimal OA, normal alignment): 70-80% pain relief, 70-80% graft survival at 10 years; This patient's outcomes likely inferior due to grade 2 OA and borderline age - perhaps 60-70% pain relief, uncertain graft survival; MAT does NOT cure arthritis or regenerate cartilage - it may slow progression but won't reverse existing damage; Realistic goal: delay arthroplasty 5-10 years, reduce pain, improve function; Will likely still require knee replacement eventually, but at older age (58-60 vs 50-55); Alternative: conservative management (physio, weight loss, activity modification, analgesia) then knee replacement in 5-10 years - may be more predictable than complex MAT + HTO with uncertain results
Combined procedure post-operative protocol - longer recovery than MAT alone: Initial 6 weeks: non-weight bearing or touch-toe weight bearing (HTO bone healing requirement), ROM limited to 0-90° (protect both osteotomy and MAT), brace for comfort; 6-12 weeks: progressive weight-bearing as osteotomy heals (X-ray confirmation), advance ROM to full; 3-6 months: strength and functional rehabilitation, low-impact activities; 12-18 months: full return to activities if achieved (longer than MAT alone which is 9-12 months, due to combined procedure); Complications to monitor: stiffness (higher risk with combined procedure, 10-15%), HTO nonunion (5-10%), graft extrusion or failure, infection, neurovascular injury
COMMON PITFALLS
Performing MAT without correcting varus malalignment - guaranteed graft failure: Single biggest error in MAT surgery is ignoring alignment; Varus deformity overloads medial compartment and causes graft extrusion/failure within 2-3 years regardless of perfect surgical technique; Must assess alignment on full-length standing films (mechanical axis) in every MAT candidate; If varus greater than 3-5°, must combine with HTO or refuse MAT; Doing MAT alone in varus knee is surgical malpractice - patient will fail and blame surgeon
Not counseling realistic expectations in borderline candidate - patient dissatisfaction inevitable: This patient has multiple risk factors for poor outcome (age 48, KL grade 2, BMI 29); Quoting 70-80% success rates from ideal candidates is misleading - his outcomes will be inferior; Must explain that MAT may slow arthritis but won't cure it, may delay but won't prevent eventual arthroplasty; Overselling combined MAT + HTO leads to disappointed patient when they still have pain and eventually need replacement; Better to under-promise and over-deliver than create unrealistic hopes
Not offering alternative of conservative management followed by arthroplasty - informed consent requires options: Some surgeons push complex MAT + HTO without discussing that conservative management + future TKR may be simpler and more predictable; At age 48, patient could manage conservatively for 5-10 years then have TKR at 55-58 (acceptable age for knee replacement); TKR has 90-95% satisfaction and 90% 15-year survival - more predictable than MAT + HTO in borderline candidate; Informed consent requires discussing this alternative, letting patient weigh risks/benefits of complex joint preservation vs accepting arthroplasty; Some patients choose preservation attempt, others choose conservative management - both valid
Single-stage combined procedure without considering patient fitness and complexity - risk of complications: Combined MAT + HTO is major surgery - 3-4 hours operative time, significant blood loss potential, prolonged anesthesia; Requires fit, motivated patient who can tolerate extended surgery and complex rehabilitation; If patient has comorbidities (cardiac, pulmonary), borderline fitness, or limited social support, staged approach safer; Also consider surgeon experience - combined procedure technically demanding; Don't attempt single-stage if not experienced with both HTO and MAT independently - better to stage or refer to specialist center
Ignoring BMI 29 as risk factor - obesity predicts poor MAT outcomes: BMI greater than 30 is relative contraindication to MAT (mechanical overload, poor healing, higher failure rate); This patient at 29 is borderline but still concerning; Should counsel weight loss before surgery if possible - reducing to BMI 25-27 would improve outcomes; Proceeding at BMI 29 acceptable but adds to risk profile; Not discussing weight as modifiable risk factor is missed opportunity to optimize patient and improve results
FURTHER QUESTIONS
"If you choose to stage the procedures, which would you do first and why?"
"How do you size the meniscal allograft?"
"What are the contraindications to MAT?"
"What would you do if after HTO his pain is much improved - would you still do the MAT?"
"What alignment are you targeting with the HTO?"
CLINICAL SCENARIOCritical
Scenario 3: Early Meniscal Allograft Extrusion - Graft Failure Management
CLINICAL PROMPT
"You performed a medial meniscal allograft transplantation 4 months ago in a 38-year-old woman who had post-meniscectomy syndrome. She was an ideal candidate - young, minimal arthritis (KL grade 1), normal alignment on full-length films, stable knee, BMI 24. You used a fresh-frozen allograft with bone bridge technique for root fixation. The surgery went well - you achieved good graft seating, secure bone fixation, and peripheral sutures to the capsule. Post-operatively, she followed the protocol meticulously - non-weight bearing for 6 weeks, progressive ROM, no pivoting or deep squatting. She initially did well with reducing pain. However, at her 4-month follow-up, she reports that over the past 4-6 weeks her medial knee pain has returned and is worsening. On examination, she has medial joint line tenderness and a small effusion. You order an MRI which shows significant meniscal extrusion - the graft body has extruded laterally (radially) beyond the tibial margin by 5mm, and the T2 signal within the graft is increased suggesting degeneration. The bone bridge appears healed in the tibial tunnel. Looking back at the operative note, you confirmed intraoperatively that sizing was within 5% of the contralateral meniscus dimensions. The patient is understandably upset and asks what went wrong and what can be done. How do you approach this consultation and what are the management options?"
PRACTICAL APPROACH
This is a distressing complication - early meniscal allograft extrusion at 4 months suggesting graft failure despite apparently ideal patient selection and surgical technique. I need to approach this consultation with empathy, honesty, and a systematic plan. First, I would acknowledge the patient's frustration and validate that this is an unexpected outcome given that she was an ideal candidate and followed the protocol perfectly. I would explain that meniscal allograft transplantation has a 70-80% success rate at 10 years, meaning 20-30% of grafts fail even in ideal circumstances - unfortunately, she appears to be in that group despite everything being done correctly. Graft extrusion (radial subluxation beyond the tibial margin) is a recognized failure pattern, occurring in 15-20% of MAT cases, and is a poor prognostic sign associated with return of symptoms and accelerated arthritis. I need to determine why this occurred and what can be done. Step 1 is to systematically review potential causes of early extrusion: (1) Sizing error - though operative note states within 5%, I would re-measure the graft dimensions from the pre-operative scans and compare to her native meniscus to absolutely confirm - even 1-2mm oversizing can cause extrusion; (2) Technique issues - was the graft seated properly at the time? Was there any peripheral detachment? I would review the operative photos/video; (3) Missed malalignment - though pre-operative films showed normal alignment, I would repeat full-length standing films now to confirm mechanical axis is still neutral (sometimes subtle varus was missed or has progressed); (4) Root fixation failure - though MRI shows bone bridge healed, was the initial position anatomic? Non-anatomic root position (too anterior or posterior) can cause extrusion; (5) Peripheral detachment - sutures to capsule may have pulled through or failed, allowing radial extrusion; (6) Biological failure - graft may have failed to integrate/heal to the peripheral capsule, or patient's biology may not support graft incorporation (this is idiopathic in 10-15% of cases). Having explained these possibilities, I would outline management options: (1) Observation with conservative management - accept that the graft has failed and manage symptomatically with activity modification, physiotherapy, analgesia, possible corticosteroid injection; acknowledge that she is back to post-meniscectomy state; this may delay but not prevent eventual arthritis and possible future arthroplasty; (2) Revision MAT - technically possible but has significantly worse outcomes than primary MAT (only 40-50% success vs 70-80% primary); requires removing failed graft, re-preparing meniscal bed (which may be scarred), obtaining new size-matched allograft, and repeating surgery; only reasonable if a clear correctable cause is identified (e.g., definite sizing error, or missed malalignment now corrected with HTO); high risk of repeat failure; (3) Arthroscopic graft debridement/partial meniscectomy - if graft is partially extruded but portions remain functional, could arthroscopically debride degenerated portions and leave viable tissue; temporizing measure, not curative; (4) Acceptance and plan for future arthroplasty when symptoms warrant - at 38 years old, she has time before arthroplasty becomes necessary; may get 5-10 years with conservative management before considering TKR. I would recommend repeating full-length alignment films to absolutely exclude subtle malalignment, and reviewing all pre-operative imaging and operative details to identify any correctable technical factor. If no clear cause identified and alignment confirmed neutral, this likely represents biological failure (poor graft incorporation, peripheral detachment due to poor healing) which is a known risk that occurred despite optimal surgery. In this scenario, I would favor conservative management initially - accept the graft has failed, manage symptoms, and defer decision on revision MAT vs future arthroplasty until symptoms dictate. Revision MAT at 4 months is premature and unlikely to succeed without identifying correctable cause. I would provide regular follow-up, symptom management, and counsel that she will likely need some form of intervention in future (revision MAT vs arthroplasty) but timing depends on symptom severity. This is a difficult conversation but honesty, empathy, and systematic approach are critical to maintaining patient trust despite poor outcome.
KEY CLINICAL POINTS
Meniscal extrusion after MAT - recognized failure pattern occurring in 15-20% of cases: Extrusion = radial subluxation of graft beyond tibial margin (normal meniscus should be contained within tibial plateau); Measured on coronal MRI - extrusion greater than 3mm is abnormal, greater than 5mm indicates failure; Poor prognostic sign - extruded meniscus cannot transmit load effectively, loses biomechanical function; Associated with return of symptoms (pain, effusion), accelerated cartilage degeneration, and eventual graft failure; Early extrusion at 4 months suggests either technical error or biological failure of graft to integrate
Systematic evaluation of causes of early graft extrusion - detective work required: (1) Sizing error: oversized graft (even 1-2mm) can extrude - re-measure pre-operative scans to confirm dimensions; (2) Malalignment: missed varus or valgus deformity causes compartment overload - repeat full-length standing films to check mechanical axis; (3) Root fixation malposition: non-anatomic root position (too anterior/posterior) alters biomechanics and causes extrusion - review bone bridge position on MRI; (4) Peripheral detachment: sutures pulled through capsule or failed to heal - look for gaps on MRI between graft and capsule; (5) Technique issues: was graft seated properly intra-op? Review operative photos/video if available; (6) Biological failure: idiopathic poor integration (10-15% cases) - patient's biology doesn't support graft healing despite perfect technique
Honest communication with patient - managing expectations and maintaining trust after complication: This is devastating for young patient who was ideal candidate and followed protocol perfectly; Must acknowledge frustration and validate that outcome is unexpected and disappointing; Explain that MAT has 20-30% failure rate even in ideal circumstances - she is unfortunately in that group; Avoid defensive language or blame (e.g., don't blame patient compliance or suggest she did something wrong); Be honest that this may represent biological failure that was unpredictable and unpreventable; Systematic approach (investigating causes, reviewing images) shows thoroughness and maintains patient confidence; Goal is to maintain therapeutic relationship despite poor outcome so patient trusts you for ongoing management
Management options for failed MAT with extrusion - balancing salvage vs acceptance: (1) Conservative management: accept failure, symptom control (physio, analgesia, activity modification), delay further surgery - reasonable first-line; (2) Revision MAT: technically possible but poor outcomes (40-50% success vs 70-80% primary) - only if correctable cause identified (sizing error, malalignment now correctable); high risk of repeat failure, second surgery, prolonged recovery - should be last resort; (3) Arthroscopic debridement: if partial extrusion, debride degenerated portions, leave viable tissue - temporizing, not curative; (4) Acceptance and future arthroplasty: at 38 years, patient may get 5-10 years conservative management before TKR needed; TKR has 90-95% satisfaction and predictable outcomes; Recommendation: conservative management initially, reassess at 6-12 months, consider revision MAT only if clear correctable cause and patient remains symptomatic despite conservative treatment
Revision MAT decision-making - when is it justified? Very limited indications: Only reasonable if: (1) Clear correctable technical error identified (definite sizing error, missed malalignment now corrected with HTO, root malposition that can be re-positioned anatomically); (2) Patient remains highly symptomatic despite conservative management (e.g., at 12-18 months post-primary MAT, still severe pain limiting function); (3) Patient understands poor success rate (40-50%) and risk of repeat failure, accepts need for possible further surgery; (4) Surgeon has expertise in revision MAT (technically demanding - scarred tissue, poor biology); Contraindicated if: no correctable cause identified (suggests biological failure - will recur), early time point (less than 12 months - too soon, graft may still improve), patient developing arthritis progression (now KL 3-4), patient unrealistic expectations; At 4 months, revision MAT is premature - should observe for 12-18 months with conservative management first
COMMON PITFALLS
Immediately offering revision MAT at 4 months without systematic evaluation - recipe for repeat failure: Jumping to revision surgery without understanding WHY the primary graft failed will result in same outcome; Must systematically investigate: sizing, alignment, technique, biology before considering revision; Early revision at 4 months is premature - graft may still remodel, symptoms may improve with time and therapy; Revision MAT has poor success rate (40-50%) and should be last resort, not first option; Better to observe for 12-18 months with conservative management, then reassess if patient still severely symptomatic
Defensive communication or blaming patient for failure - destroys therapeutic relationship: Patient was ideal candidate who followed protocol perfectly - blaming her is indefensible; Saying 'you must have overdone it' or 'you didn't follow restrictions properly' when she clearly did will cause anger and mistrust; Some graft failures are biological and unpredictable - no one's fault; Defensive language ('I did everything right, it's not my problem') alienates patient and may lead to complaint/litigation; Better approach: acknowledge disappointment, explain biological failure occurs in 20-30%, maintain empathy, focus on path forward
Not re-evaluating alignment and sizing - missing correctable cause: Although pre-op films showed normal alignment, must repeat full-length standing films now - subtle malalignment may have been missed or may have progressed; Extrusion often caused by compartment overload from varus/valgus - if now identified, could consider revision MAT + HTO; Similarly, must re-measure graft sizing from pre-op scans - even 1-2mm oversizing can cause extrusion; If correctable technical error identified (sizing mistake, missed malalignment), this changes management from conservative to potential revision; Not re-investigating means missed opportunity to salvage with corrective surgery
Offering revision MAT without correctable cause identified - high risk of repeat failure: If no sizing error, no malalignment, no root malposition identified, this likely represents biological failure (poor graft integration to capsule); Biological failure will recur with revision MAT - patient's biology doesn't support graft healing; Revision in this scenario has very poor success (probably less than 30-40%) and subjects patient to another major surgery, prolonged recovery, high likelihood of failure again; Should counsel that revision not recommended if no correctable cause, focus on conservative management and eventual arthroplasty; Doing surgery for sake of 'doing something' when not indicated harms patient
Not counseling about eventual arthroplasty option - patient needs realistic long-term plan: At 38 years old with failed MAT, patient is back to post-meniscectomy state and will likely develop progressive arthritis over 5-10 years; Avoiding discussion of eventual TKR leaves patient without long-term plan and understanding; Should counsel: with conservative management may control symptoms for 5-10 years, when pain becomes severe will consider TKR (at age 45-50, reasonable age for knee replacement), TKR has excellent outcomes (90-95% satisfaction); This gives patient realistic expectation that there is a definitive solution (TKR) if MAT has failed, reduces anxiety about 'what happens now'; Some patients prefer this certainty over gambling on revision MAT with 40-50% success rate
FURTHER QUESTIONS
"What are the common causes of meniscal allograft extrusion?"
"What would make you consider revision MAT in this patient?"
"How do you size a meniscal allograft?"
"What is the success rate of revision MAT compared to primary MAT?"
"At what age would you consider knee arthroplasty in this patient if conservative management fails?"
Guidelines, Registries & Global Practice
Global Epidemiology
MAT remains a low-volume, specialist procedure performed in selected younger patients (typically third-to-fifth decade, male predominant in published cohorts) who have had total or subtotal meniscectomy. Absolute case numbers are small worldwide compared with primary meniscal surgery, and most evidence is Level III-IV observational data from high-volume centres.
Society and Consensus Positions
| Body | Position on MAT |
|---|---|
| ESSKA / European consensus | Endorses MAT for symptomatic post-meniscectomy compartment pain in a stable, aligned, non-arthritic knee; emphasises correcting alignment/instability and acceptable cartilage status |
| NICE (UK) | Interventional procedures guidance supports MAT with normal arrangements for consent, audit and outcome registration, recognising it is specialised |
| AAOS (US) | Frames MAT as joint preservation in carefully selected younger patients; stresses limited high-level evidence and shared decision-making |
| ICRS / cartilage community | Treats MAT as part of an integrated joint-preservation algorithm, often combined with cartilage repair and/or osteotomy |
Across societies the message is consistent: strict patient selection (cartilage, alignment, stability, sizing) drives outcome, and chondroprotection should not be promised.
Registry and Outcome Tracking
- There is no large dedicated international MAT registry equivalent to arthroplasty registries; outcome data come from institutional series and systematic reviews.
- Several national systems (e.g. UK practice) encourage prospective audit/outcome registration of MAT given its specialised, evidence-limited nature.
- Tissue banks and national transplant/tissue authorities govern allograft procurement, screening and traceability.
High- vs Limited-Resource Practice Variation
- High-resource settings — access to screened fresh-frozen/cryopreserved allografts, MRI/3D sizing, combined osteotomy/ligament/cartilage procedures, and structured rehabilitation.
- Limited-resource settings — allograft availability and tissue-banking infrastructure are the main constraints; MAT is often unavailable, and management defaults to activity modification, unloader bracing, osteotomy where indicated, and eventual arthroplasty.
- Graft cost, regulatory tissue-banking requirements and surgeon experience are the principal global determinants of access.
MENISCAL TRANSPLANT
Clinical summary
Indications (YAPS)
- •Young (under 50)
- •Alignment normal (or correct)
- •Post-meniscectomy pain
- •Small arthritis (KL 2 or less)
Contraindications
- •Advanced OA (KL 3-4)
- •Uncorrected malalignment
- •Inflammatory arthritis
- •Unstable knee
Sizing
- •Critical for success
- •Match within 5%
- •Pollard method (X-ray)
- •Or MRI contralateral
Technique
- •Fresh-frozen allograft
- •Bone plug/bridge preferred
- •Suture to capsule
- •70-80% pain relief