Allograft | Post-Meniscectomy Pain | Joint Preservation
Indications
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.
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!
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!
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.
- 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
- 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
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
- 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%
- 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
- 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
- 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
- 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
Decision Algorithm

Exam Viva Scenarios
Use these scenarios to practise clinical reasoning and management decisions
Scenario 1: Post-Meniscectomy Pain
"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?"
Scenario 2: Borderline Candidate with Malalignment - Combining MAT with HTO
"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?"
Scenario 3: Early Meniscal Allograft Extrusion - Graft Failure Management
"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?"
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