Meniscus : Much more than an important shock absorber
Each knee has two menisci. Along the inside of the knee is a moon-shaped structure, while on the outside it forms an open circle. They serve three functions: pressure distribution, sliding, and stability. The inner meniscus bears about 50% of the weight in the knee, with the remainder supported by the cartilage. The outer one carries even more, approximately 70%. The meniscus evenly distributes the weight over a larger surface area. Removing it would concentrate all the weight on the small area where the cartilage of the femur and tibia meet. Additionally, the meniscus allows these cartilages to glide over each other with minimal resistance. Without the menisci, the cartilage would experience very high localized pressure, leading to damage. Moreover, the menisci contribute significantly to the stability of the knee joint. In cases of an anterior cruciate ligament tear, it’s only the inner meniscus that keeps the heads of the femur and lower leg properly aligned when the leg bends. This places it under substantial stress, explaining why it wears out more rapidly in individuals lacking an anterior cruciate ligament.
Partial Meniscectomy
If the meniscus has suffered irreparable damage, the torn portion is removed during keyhole surgery using special instruments, forceps, and shavers. Only the damaged part is removed, leaving the healthy portions intact. Partial meniscectomy is the most commonly performed arthroscopic procedure worldwide, with favorable results in more than 90% of patients. However, there is an increased risk of further joint wear in these patients in the long term (over 20 years). In a limited number of cases, patients may experience pain, swelling, or accelerated cartilage wear shortly after the procedure. These patients may be considered for additional treatments such as meniscal replacement solutions (see below), osteotomy, or even prosthetic surgery. Degenerative (wear and tear) meniscus tears often occur after the age of 50 (25%) and are best treated non-surgically in the first 3 months with physiotherapy, cycling, pain relief, and possibly an injection. Most patients will show improvement after 3 months and will not require surgery. In cases of persistent complaints, an arthroscopy and partial meniscectomy can provide relief.
Meniscus Suture
In some cases, a meniscus tear can be repaired with a meniscus suture. Unfortunately, not all tears qualify, only tears in young patients in a well perfused area. During exploratory surgery, the tear is stitched up using advanced repair techniques. The success rates of this operation are about 80%.
Save the meniscus when possible: Advanced repair.
Meniscus Scaffold
Today, our primary focus is on preserving the meniscus and its functionality. One approach is to use a scaffold or a porous artificial meniscus, where the body’s own cells can settle and grow into a new structure resembling a meniscus. Currently, this technique is only suitable for partial or smaller painful defects. The procedure is conducted through keyhole surgery. There is now over 10 years of experience with this scaffold. The short-term outcomes were recently published in the American Journal of Sports Medicine.
Meniscus Transplantation
Young individuals experiencing pain with a severely damaged or completely removed meniscus, but whose knee cartilage is still relatively healthy, are ideal candidates for meniscus transplantation. This procedure involves replacing the entire meniscus with a donor meniscus, making it suitable for larger injuries. The surgery is performed using keyhole techniques.
The drawback of meniscus transplantation, of course, is the requirement for a suitable donor meniscus. A waiting period of 6 to 24 months is not uncommon. We have accumulated over 20 years of experience with meniscus transplants, which have been documented in all major orthopedic journals.
Meniscal Prostheses
This innovative technique is currently available, but it is not yet covered by insurance. The polyurethane artificial meniscus offers a solution for older individuals where the inner or medial meniscus had to be largely removed. In this scenario, the worn meniscus is replaced with a plastic meniscal prosthesis.