Meniscus and Arthroscopy

Circumferential meniscal fibers and root attachments contribute to load transmission. Tear location and pattern, tissue quality, and stability affect loss of function and repairability. Arthroscopy should assess stability by probing as well as the visible shape.

Degenerative and acute traumatic tears require different considerations. Review symptoms, locking, and associated arthritis. If surgery is needed, understand why functioning tissue should be preserved where possible. Root and large radial tears merit particular attention because they interrupt circumferential continuity.

The meniscus is not merely a shock absorber; it maintains contact area, hoop-stress transmission, and joint stability. Radial and root injuries can interrupt the continuity of circumferential fibers, so calling a tear small does not establish its functional effect. In an ACL-deficient knee, the medial posterior horn provides additional stabilization, which makes it important to assess ligament and meniscal pathology together.

Document tear location, configuration, tissue quality and displacement, symptoms, and mechanism to evaluate preservation options. The AAOS 2024 guideline for acute isolated injuries emphasizes preserving functional tissue where possible, but it is not a guideline directly applicable to degenerative or root tears. Distinguish degenerative MRI signals from the actual cause of symptoms, and differentiate lavage or debridement intended to treat arthritis itself from treatment of a displaced tear.

Repair techniques differ in accessible locations and neurovascular risks. For inside-out repair, consider posterior exposure and protection; for outside-in repair, the needle path; for all-inside repair, insertion depth and device direction. Before choosing a device, assess whether the tear can be reduced and fixed stably.

Weight-bearing and motion after repair depend on tear pattern, fixation stability, root repair, and associated operations. One rehabilitation schedule does not fit every repair. Compare study populations and definitions of clinical failure when reading success rates.

Inside-out, outside-in, and all-inside repair differ in access direction and fixation devices. The feasible technique depends on whether the tear involves the anterior horn, body, or posterior horn, as well as its configuration and tissue thickness and quality. Assess suture direction and spacing, tear reduction and tension, and the position of posterior neurovascular and soft-tissue structures. Fewer skin incisions do not mean that all-inside repair carries no risk.

Do not restrict repairability to a single historical vascular-zone measurement. Healing depends on tissue quality, tear configuration, fixation stability, concomitant ACL reconstruction, and rehabilitation conditions together. Surgery and protection for root, radial, and complex tears may differ from longitudinal tears. Separate the mechanism of biological augmentation from its clinical benefit, and individualize protection based on the operative record and loading conditions.

When considering resection, distinguish an unstable torn fragment from functioning surrounding tissue. Check the stability and peripheral continuity of the remaining meniscus, and understand how tissue removal affects contact area and stress.

Degenerative lesions may coexist with arthritis, cartilage damage, and other pain generators. Removing a torn fragment arthroscopically does not establish that the overall course of arthritis has changed. Distinguish resection indications and results from outcomes of repairable acute tears.

Partial meniscectomy removes unstable fragments that are difficult to reconstruct while preserving functioning tissue and a stable peripheral rim. Even a decision to smooth an area slightly further can change contact area and load distribution, so check the continuity of residual fibers and the root. It is helpful to explain the resection in terms of the function of remaining tissue rather than the size of the removed fragment.

For degenerative tears, distinguish MRI findings from pain and locking, and consider the role of nonoperative care, including exercise and activity modification. Intermittent clicking is not equivalent to a displaced, locked knee that cannot be extended. If surgery is chosen, specify the target symptoms, coexisting arthritis and cartilage status, and expected limitations, and explain that pain relief does not imply prevention of arthritis progression.

Distinguish an incidental discoid meniscus from one causing pain, locking, or snapping. Shape alone does not establish the source of symptoms. Peripheral attachment stability and associated tears are important for planning.

Saucerization aims to leave tissue that functions stably. Rather than relying on a fixed rim-width number, assess the remaining rim, tissue condition, and instability on probing. An unstable peripheral rim may also require repair.

A discoid meniscus requires assessment not only of shape but also peripheral attachments and mobility, thickness, and tissue quality. MRI morphology provides diagnostic information but does not determine whether symptoms will occur or whether surgery is indicated. Establish when snapping, an extension block, or recurrent swelling occurs in a child, and distinguish an asymptomatic anatomical variant from a symptomatic tear or instability.

Treatment aims to preserve stable tissue and restore loading closer to normal. If the peripheral rim remains unstable after saucerization, assess stability and consider repair. A fixed rim width or total meniscectomy for the Wrisberg type should not be applied uniformly to all patients. The width and extent retained depend on body size, tissue condition, and tear pattern; symptom improvement and long-term joint preservation are followed separately.

The posterior root transmits circumferential fiber forces to the tibia, maintaining hoop function. An attachment tear or nearby radial tear can substantially impair load distribution despite retained tissue. In cadaver testing, medial root-tear contact pressure resembled total meniscectomy, a finding specific to experimental conditions. Evaluate degenerative medial injuries separately from lateral root lesions accompanying ACL injury, considering their different contexts and stabilizing structures.

On MRI, assess root continuity, radial defects, and extrusion in several planes alongside cartilage and subchondral bone. Extrusion alone neither establishes a tear nor determines repair suitability. Use weight-bearing imaging to assess arthritis extent and limb alignment, relating tissue quality and reducibility to symptoms, activity goals, and rehabilitation circumstances. Assess whether advanced cartilage damage and loading conditions limit benefit rather than relying on age alone.

Plan repair to reduce tissue to its anatomical attachment and restore functional continuity. If the tissue is scarred posteromedially or under tension, fixation to a nearby convenient location may be insufficient. Transtibial pullout and anchor approaches have different access and fixation conditions; consider associated ACL tunnels and other hardware. Assess reduction, fixation, and tension during movement after repair, avoiding fixation away from the native footprint.

Observational comparisons of selected patients found less arthritis progression and arthroplasty conversion after repair, but selection bias and small samples limit interpretation. Repair does not guarantee prevention of OA or normalization of extrusion. Follow alignment, remaining cartilage, extrusion changes, and symptoms together; individualize loading, flexion, and resistance exercise to fixation and accompanying procedures.

A ramp lesion involves the meniscocapsular or meniscotibial connections at the peripheral posterior horn of the medial meniscus and should be assessed with ACL injury. The surface may appear continuous while an inferior connection is damaged or concealed beneath thin tissue. Its location differs from a posterior root's tibial attachment, so the terms are not interchangeable. Assess tear location and tissue mobility, recognizing the posterior horn's increased stabilizing role in ACL deficiency.

Even without a clear MRI lesion, do not conclude assessment from the anterior arthroscopic view alone. If posterior horn instability is suspected during ACL reconstruction, use posterior visualization through the notch and probing, with safe posteromedial access when necessary to inspect concealed connections. Protect adjacent structures, including the saphenous nerve and vessels, during portal creation and suturing. Document lesion length, depth, meniscotibial continuity, probe-induced displacement, and reducibility.

Cadaver studies showed that peripheral posterior horn disruption can increase anterior and rotational laxity in ACL-deficient and reconstructed knees, supporting a mechanical role for concomitant repair. Experimental changes do not establish the clinical importance of every small lesion. Consider repair after inspecting displacement, disrupted attachments, and tissue quality. Avoid overlooking associated posterior horn instability while focusing only on ACL tunnels and tension.

A randomized trial finding similar results between repair and abrasion plus trephination for stable ramp lesions during ACL reconstruction did not compare repair with no treatment. Do not extend its findings to large unstable lesions or isolated injury. Base repair decisions on stability, morphology, and healing conditions, then reassess displacement and tension during movement after fixation. Rehabilitation should combine ACL recovery with meniscal protection rather than applying one schedule to all ramp lesions.

A parameniscal cyst is a fluid collection near the meniscus, often connected to a horizontal tear or a complex tear with a horizontal component. A palpable lump at the joint line does not establish the cause of pain by itself. Symptom location, changes in the lump with flexion, tenderness and the MRI connection between the tear and cyst are compared, while other soft-tissue masses are considered.

MRI assessment includes cyst location and size, tear length, the quality of the remaining upper and lower leaflets, and the capsular connection. Lateral cysts require attention to the collateral ligament and popliteus anatomy; incision and instrument routes follow the cyst's actual location. A small asymptomatic cyst and a large painful cyst are not managed identically.

When surgery is considered, cyst drainage and treatment of the connected tear are explained separately. A residual tract and tear can contribute to recurrence after decompression or excision, but this does not justify broad removal of normal meniscal tissue. Tissue quality and stability guide preservation and repair, while cyst location determines the safe access route and treatment extent.

A retrospective comparison of 241 cases published in 2016 found more recurrence after entirely arthroscopic decompression than after treatment including cyst excision, with large cysts and longer tears associated with recurrence. Selection differences and older techniques may affect these findings, so its size thresholds are not applied universally. Counseling addresses symptom improvement, the function of the retained meniscus and the possibility of cyst recurrence.

Meniscal allograft transplantation (MAT) is considered after loss of a functional meniscus when pain and functional limitations arise in the affected compartment. Previous meniscectomy alone is not an indication. Assessment includes resection extent, remaining tissue function, the painful compartment, joint space on weight-bearing images and the patient's activity goals.

Ligament stability, the load-bearing axis and cartilage status are considered together for graft function. Hip-to-ankle radiographs identify compartment loading, and ACL, PCL and collateral function are assessed. When osteotomy, ligament reconstruction or cartilage treatment is needed, each procedure is connected to the problem it addresses and its distinct rehabilitation restrictions. A single historical cartilage grade is not applied as an absolute contraindication whenever cartilage injury is present.

Graft sizing, root position and fixation are central planning variables because they may influence meniscal tension and extrusion. Implanting a normally shaped graft and restoring physiological load distribution are different outcomes. Follow-up separates pain and function scores, graft status and extrusion, joint space, and additional operations.

Long-term cohorts show that improved function after MAT and progression of extrusion or joint-space narrowing may follow different courses. A 2019 study with mean 12.3-year follow-up found greater joint-space loss with extrusion but no clinical-score difference, while a small 2021 study suggested a relationship between chondroprotection and extrusion. These observations do not justify promising that MAT prevents osteoarthritis progression or restores a normal knee in every patient.