Meniscal Repair

Meniscal function includes load transmission, shock absorption, joint stability, proprioception and lubrication. The meniscus converts axial compressive load into circumferential hoop stress resisted by its strong peripheral collagen fibres. Loss of meniscal tissue removes this hoop mechanism, raising peak tibiofemoral contact stress (roughly a 4-7 fold rise after total meniscectomy) and accelerating osteoarthritis.

Meniscal tears are among the most common knee injuries, showing a bimodal pattern: young patients with traumatic vertical/longitudinal tears (often with ACL injury) and older patients with degenerative complex tears. The modern philosophy is meniscus preservation wherever the tear is biologically repairable.

Indications for Repair

• Tear pattern: Vertical longitudinal (including bucket handle)
• Location: Red-red or red-white zone (peripheral)
• Length: Greater than 10mm
• Stability: Unstable tear (greater than 3mm displacement)
• Tissue quality: Good meniscal tissue, not degenerative
• Patient factors: Younger, active patients
• ACL reconstruction: Concurrent ACL recon improves healing

Contraindications to Repair

• White-white zone (avascular)
• Complex or degenerative tears
• Significant tissue loss
• Poor tissue quality
• Chronic tears (may still attempt but lower success)
• Older, low-demand patients (relative)

Healing potential is dictated by blood supply. The meniscus receives a peripheral supply from the perimeniscal capillary plexus (branches of the medial and lateral geniculate arteries), penetrating only the outer 10-30% (approximately 3mm) of the meniscal width. The inner portion is essentially avascular and nourished by synovial diffusion.

• Red-Red Zone — outer 3mm, vascular, best healing potential.
• Red-White Zone — middle zone, partial vascularity, intermediate healing.
• White-White Zone — central, avascular, poor intrinsic healing.

A repairable tear approximates two vascularised edges so that a fibrovascular healing response can bridge the defect. This is why tear location (zone), pattern (vertical/longitudinal apposes well; complex/horizontal does not) and tissue quality are the dominant determinants of success, and why biological augmentation (marrow venting, fibrin clot, PRP, trephination) is used to stimulate healing in less vascular zones.

• History — twisting/pivoting injury (traumatic tears) or insidious onset (degenerate); joint-line pain; true mechanical locking or catching suggests a displaced (bucket-handle) fragment; recurrent effusions.
• Examination — joint-line tenderness, positive McMurray and Thessaly tests, effusion, and a possible block to terminal extension with a locked bucket-handle tear. Assess ligamentous stability (Lachman/pivot-shift) as concurrent ACL injury is common and influences healing.
• Root tears — may present with a sudden pop and posterior knee pain, rapid functional decline and meniscal extrusion; biomechanically equivalent to total meniscectomy if untreated.

• MRI — investigation of choice; defines tear pattern, length, zone (vascularity) and rim width, and detects root tears (radial gap, "ghost sign", meniscal extrusion over 3mm). Helps predict repairability before surgery.
• Weight-bearing radiographs — assess limb alignment and degenerative change, which strongly influence whether a tear is repairable or better resected; long-leg views if realignment osteotomy is considered.
• Diagnostic arthroscopy — the definitive assessment of tissue quality and stability (probing for displacement over 3mm). The final repair-versus-resect decision is frequently made intra-operatively.

A locked or painful knee with a suspected meniscal tear has a broad differential. The table below contrasts the key mimics an examiner expects you to exclude before committing to meniscal repair.

The route of the repair (inside-out, all-inside, outside-in) determines access, but the suture configuration determines strength - and this is a favourite examiner distinction. The meniscus resists load through circumferentially oriented collagen bundles, so the strongest construct is the one that captures those fibres perpendicularly and resists pull-through.

• Vertical mattress (vertical divergent) - the biomechanically strongest and the reference configuration, quoted in the viva above. Passing the two limbs vertically across the tear snares the circumferential collagen bundles at right angles, giving the highest load-to-failure and best resistance to suture pull-out. It is the workhorse construct for peripheral vertical longitudinal and bucket-handle tears.
• Horizontal mattress - technically easier and useful where a vertical pass is awkward (e.g. tight posterior horn), but it lies parallel to the collagen bundles, captures fewer fibres and is weaker, so it is generally reserved as a supplement rather than the primary fixation.
• Reducing gapping - "stacked" sutures on both the femoral and tibial surfaces of the meniscus balance reduction and resist the tear opening under load; alternating surfaces avoids over-tightening one face. Sutures are typically spaced a few millimetres apart along the tear.
• Material and devices - non-absorbable braided suture is standard. Modern all-inside implants achieve strength through a suture-based construct with a low-profile capsular backstop and a sliding, self-locking knot; the historical weakness (and chondral abrasion) belonged to the rigid first- and second-generation arrows/darts, not to current suture-based devices. Construct strength therefore now depends more on suture number and orientation than on the delivery route.

• Repair failure / re-tear — the principal concern; pooled long-term failure is roughly 23% (Nepple meta-analysis), and revision repair has substantially lower success (about 40-50%). Failure is more likely with white-zone, complex, chronic and older-patient tears.
• Saphenous nerve injury (medial inside-out) and common peroneal nerve injury (lateral inside-out) — prevented by a protective posterior incision and direct suture retrieval; nerve symptoms are reported in around 9% with inside-out repair.
• Implant-related problems (all-inside) — chondral abrasion from rigid/older devices, implant migration, breakage and local soft-tissue irritation.
• Other — stiffness/arthrofibrosis, infection, persistent effusion, and progression to osteoarthritis if the repair fails and meniscectomy becomes necessary.
• Post-meniscectomy syndrome — pain and early arthritis after tissue loss; in young patients this may ultimately be salvaged with meniscal allograft transplantation.

The pooled failure figures quoted throughout this topic (roughly one in four by five years) depend entirely on how "failure" is defined, and this is a subtle exam point. Healing is not all-or-nothing, and the way it is assessed changes the reported success rate.

• Clinical versus anatomic failure - most large series (including the Nepple meta-analysis cited above) define failure pragmatically as reoperation or symptomatic clinical failure. A repair can be anatomically incomplete yet asymptomatic, or symptomatic from another cause; the two definitions do not always coincide, so quoted "healing rates" must be read against the definition used.
• Grades of healing - second-look assessment classically grades repairs as complete healing (the tear line bridged across the full thickness), partial/incomplete healing (a stable but not fully united tear), and failed/no healing. A partially healed, stable, asymptomatic meniscus is usually regarded as a clinical success.
• Why standard MRI over-reads failure - a healed meniscus frequently retains persistent increased intrameniscal signal reaching the articular surface because fibrovascular scar and granulation tissue behave like a residual tear on conventional sequences. Standard MRI therefore overestimates failure and is unreliable for confirming healing. MR or CT arthrography is more accurate: intra-articular contrast tracking into the repair site indicates a persistently unhealed cleft, whereas failure of contrast to enter suggests healing.
• Second-look arthroscopy remains the reference standard for judging structural healing and tissue quality, but it is invasive and reserved for research or for patients returning to theatre for another reason. Because of this, real-world "success" is usually a composite of symptom resolution, stability and functional recovery rather than proven anatomic union.

Global Epidemiology

• Meniscal tears are among the most common knee injuries, with reported surgical incidence of roughly 60-70 per 100,000 person-years in high-income settings; a clear bimodal pattern (young athletes with traumatic vertical tears, older adults with degenerative tears).
• Root tears account for an estimated 10-21% of all meniscal tears.
• The proportion of meniscal operations that are repairs (rather than meniscectomy) has risen steadily over two decades as meniscus preservation became the prevailing philosophy, but meniscectomy still predominates worldwide, especially in degenerate tears.

Guideline Comparison

Registry & Trial Evidence

• Landmark RCTs (e.g. degenerative tear trials from Finland and Scandinavia) showed arthroscopic partial meniscectomy offers no durable benefit over sham surgery or structured exercise for degenerative tears with mild OA - reinforcing repair/preservation only where biologically sensible and non-operative care for degenerate disease.
• Long-term cohort and registry data consistently link meniscectomy with accelerated radiographic osteoarthritis, underpinning the global shift toward preservation.

High- vs Limited-Resource Practice

• Well-resourced settings: ready access to MRI, arthroscopic all-inside implants and inside-out instrumentation; root repair, biological augmentation and meniscal allograft transplantation available in specialist centres.
• Limited-resource settings: MRI and proprietary all-inside devices may be scarce; outside-in and inside-out repair using standard sutures are cost-effective, durable alternatives. Meniscectomy may be chosen for pragmatic reasons, making careful patient selection and counselling on long-term arthritis risk especially important.

• Repair in the white-white (avascular) zone — Traditional teaching forbids it, but biological augmentation (marrow venting, fibrin clot, PRP, trephination) has expanded the boundary. Evidence remains low-level; the central-third tear in a young patient is the genuine grey area.
• All-inside vs inside-out durability — Equivalence reviews (Grant, Samuelsen) coexist with a 2024 meta-analysis (Villarreal-Espinosa) showing about 1.77x higher failure odds for all-inside. The signal is modest and confounded by athlete cohorts; most surgeons choose by tear location and access.
• ACL status and healing — Older literature taught markedly better healing with concurrent ACL reconstruction, yet Nepple's long-term meta-analysis found similar failure regardless of ACL status. The biological benefit is real but probably smaller and tear-pattern dependent than classically stated.
• Biological augmentation — Marrow stimulation, fibrin clot, PRP and bone-marrow aspirate are increasingly used, but high-quality RCT evidence of a healing benefit is still limited.
• Rehabilitation aggressiveness — Restricted protocols (limited flexion, protected weight-bearing) versus accelerated free rehabilitation show comparable healing in several series; the optimal protocol, especially for root and radial repairs, is unsettled.
• Lateral meniscus stability tears at ACL reconstruction — Whether to repair or leave stable, short, peripheral lateral tears (the "leave-alone" lesion) remains debated; many heal without intervention in the ACL-reconstructed knee.