The knee joint relies on the menisci, two crescent-shaped pads of fibrocartilage, to function smoothly and withstand everyday forces. These structures act primarily as shock absorbers, helping to distribute load across the knee and providing secondary joint stability. Injuries to the meniscus are among the most common orthopedic issues, resulting from acute trauma or gradual wear and tear. This article focuses on the horizontal tear, a specific pattern of meniscal injury, and the surgical strategies employed to repair and preserve the tissue.
Defining the Horizontal Meniscus Tear
A horizontal meniscus tear, also known as a cleavage tear, is distinguished by its orientation, which runs parallel to the tibial plateau surface. This tear pattern effectively separates the meniscus into superior and inferior halves, resembling an open “fish mouth” appearance. Unlike vertical or radial tears, the horizontal tear follows the circumferential fibers of the tissue.
This type of injury is frequently observed in individuals over 40 years old and is associated with degenerative changes within the cartilage rather than a single traumatic event. While a horizontal tear may initially be stable, the separated flaps can sometimes displace or fold, leading to mechanical symptoms like catching or locking in the knee. This specific cleavage pattern dictates the unique repair techniques required to compress the two split layers back together.
Criteria for Choosing Meniscal Repair
The decision to repair a horizontal tear, rather than trimming the damaged portion (partial meniscectomy), centers on preserving the long-term health of the knee joint. Preservation is preferred because removing tissue significantly alters knee biomechanics, increasing the risk of progressive arthritis over time. Not all tears can be successfully repaired, so the surgeon must assess several determining factors.
The location of the tear relative to the blood supply is a significant factor in healing potential. The outer third, known as the “red-red zone,” is well-vascularized and offers the best environment for healing. Horizontal tears often extend into the inner, avascular “white-white zone,” but modern techniques encourage repair even in these less-ideal locations by showing comparable success rates to other tear types.
Patient factors and the overall condition of the knee influence the choice of procedure. Advanced arthritic changes, typically classified as Kellgren-Lawrence grade 3 or 4, are considered a contraindication to repair. The quality of the meniscal tissue must be assessed; chronic tears with poor tissue quality may not hold sutures effectively. When possible, repair is increasingly favored, even in older patients, to maintain the meniscal function of load distribution.
Surgical Techniques for Horizontal Tear Repair
The repair of a horizontal cleavage tear is performed arthroscopically, utilizing small incisions and specialized instruments. The primary goal is to achieve circumferential compression, which involves squeezing the superior and inferior layers of the split meniscus back together. This compression creates a stable environment for healing and restores the tissue’s ability to distribute forces.
Before placing fixation, the surgeon prepares the tear edges by freshening or rasping the tissue. This process induces bleeding to introduce healing factors and blood supply to the repair site. Specialized techniques are necessary to address the parallel cleavage plane of horizontal tears, unlike the vertical sutures used for longitudinal tears. The preferred method is often an “all-inside” repair using modern devices that deploy suture anchors or specialized fasteners entirely within the joint.
These all-inside techniques allow the surgeon to place sutures in a horizontal or vertical lasso configuration, ensuring the two halves of the meniscus are tightly compressed. Traditional inside-out or outside-in techniques, which involve passing sutures through the periphery of the knee, may be used, but all-inside devices simplify achieving the necessary compression. Biological augmentation, such as platelet-rich plasma (PRP), is sometimes incorporated to promote healing at the repair site.
Post-Surgical Rehabilitation and Recovery
Recovery following a meniscal repair is a protected and carefully monitored process, significantly slower than recovery from a partial meniscectomy. Protecting the repair site from excessive load is paramount to allow the sutures to hold and the cartilage to heal. Immediately after surgery, the knee is typically protected in a hinged brace, often locked in full extension for walking to prevent harmful bending.
Weight-bearing restrictions are common, often requiring the patient to use crutches for non-weight-bearing or touch-down weight-bearing for up to six weeks. Physical therapy begins almost immediately, focusing on pain management and maintaining a gentle, protected range of motion, often restricted to 90 degrees of flexion or less. The slow progression ensures that mechanical forces do not disrupt the delicate healing process.
As the tissue demonstrates early signs of healing, typically after six weeks, the rehabilitation program advances to include increased weight-bearing and strengthening exercises. A full return to demanding activities or sports usually requires four to six months, stressing patient adherence to the structured protocol. Success depends heavily on this protected, phased recovery to achieve long-term structural integrity.