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.

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.

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)

• 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.

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.

• 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.

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.