Anatomy and Function of the Meniscus
The meniscus is a C-shaped fibrocartilaginous structure located between the femoral condyle of the femur and the tibial plateau of the tibia. There are two menisci in the knee – the medial meniscus and the lateral meniscus. The meniscus acts as a shock absorber and plays an important role in load bearing, joint stability and lubrication of the knee joint. It helps distribute weight across the knee and reduces friction between the femur and tibia during movement.
Due to their function, menisci are susceptible to tears and injuries. A tear in the meniscus can occur due to a twisting motion or sudden impact on the knee. Left untreated, a meniscal tear can lead to knee pain, swelling, locking or buckling of the joint. Eventually, there is an increased risk of developing osteoarthritis as the protective function of the meniscus is compromised.
Types of Meniscal Tears
Meniscal tears are classified based on their location and extent of damage. The common types of tears include:
– Horizontal tears: These occur parallel to the circumferential fibers of the meniscus. They are usually less symptomatic unless a displaced fragment is present.
– Vertical or longitudinal tears: These run along the vertical fibers of the meniscus and extend up from the inner margin. They are more likely to result in mechanical symptoms.
– Complex tears: These involve more than one plane of the meniscus and can be either longitudinal or transverse. They are among the most difficult to treat.
– Radial tears: These extend from the inner margin of the meniscus outward like spokes on a wheel. They are common in the avascular central portion that has limited healing potential.
– Bucket-handle tears: In this type, a fragment of the meniscus is displaced and floats freely within the joint space. This causes true mechanical symptoms like locking.
Conservative Treatment Options
Historically, treatment options for meniscal tears focused on conservative therapies like RICE (rest, ice, compression, elevation), bracing, physical therapy and injections. Small, stable tears in the vascular zone may heal with conservative treatment alone.
For persistent pain or mechanical symptoms from displaced fragments, the only option was a partial meniscectomy where the torn portion was surgically removed. However, this significantly increases the risk for developing knee arthritis in the long run due to loss of meniscal function.
Advancements in Meniscus Repair Techniques
Over the past few decades, there have been major advancements in arthroscopic techniques and devices that allow surgeons to repair torn menisci rather than resecting them whenever possible. The goals of meniscal repair are to restore normal anatomy, distribute loads across the joint and prevent the onset of arthritis.
More techniques are now available to address different types of tears based on their location within the meniscus. Outside-in repairs use needle passers and sutures introduced from the skin outside the knee joint to grasp and repair the tear from within the meniscus. Inside-out repairs involve passing sutures through cannulas from within the knee joint outwards to grasp the meniscus.
All-inside repairs rely on small pre-tied knotted sutures, darts or implants that are deployed completely within the meniscus using specialized devices and instruments introduced through small incisions. Self-reinforced/inside meniscal suturing uses meniscal tissue itself to repair tears without use of synthetic sutures.
Meniscal scaffolds made of collagen or silk materials are another option to replace resected portions and restore joint mechanics when significant volume loss has occurred. They act as a scaffold for ingrowth of host tissue over time.
Postoperative Rehabilitation
The main goals after meniscal repair include protecting the repair during the healing phase, regaining knee motion, strengthening the muscles and ensuring a gradual return to activities.
Immediate protection involves bracing, partial weightbearing, range of motion exercises and avoiding deep flexion or rotational stresses on the knee joint. Over subsequent weeks, strengthening exercises are added along with weaning off the brace as healing occurs.
Full recovery usually takes 4-6 months, with return to high impact sports requiring 6-8 months or longer depending on the extent of injury and tear location. Close monitoring by therapists prevents reinjury which could compromise the repair. Results of repair tend to be better for young patients with peripheral, horizontal tears in a otherwise healthy knee joint.
Patient Outcomes with Repair vs Resection
Several studies have compared clinical outcomes of meniscal repair versus partial meniscectomy. They found that repair allows retention of more normal knee biomechanics, reduces stresses on articular cartilage and lowers the risk of post-traumatic osteoarthritis.
Patients who underwent repair had less pain, fewer mechanical symptoms, better function scores and activity levels over long term follow up of 5-10 years compared to resection. The repaired menisci also displayed near normal magnetic resonance imaging appearance after healing.
Advanced repair techniques now enable surgeons to address tears once considered untreatable. When performed by experienced surgeons in selected patients, the results of meniscal repair match or exceed those of a partial meniscectomy with the added benefits of protecting long term joint health. With proper rehabilitation, most patients can return to high level activities within a year.
Future Directions
Continued advancements are being made to simplify suturing techniques, introduce tissue engineering solutions and promote natural healing of meniscal lesions. More biodegradable implants are under development to augment repairs without creating permanent foreign bodies within joints.
Gene therapies hold promise to stimulate cellular regeneration in avascular portions. Stem cell injections may one day provide an off-the-shelf option for healing tears or replacing resected areas. Improved diagnostic tools allow earlier detection of subtle injuries while they are still amenable to repair.
With newer approaches, more and more tears are being repaired instead of resected. Proper long term management requires close cooperation between surgeons, therapists and patients. While complete meniscal healing cannot always be ensured, repair offers the best chance to restore knee function and joint health long term compared to resection alone. Overall, advancements are dramatically improving treatment outcomes for patients with meniscal tears.