What are Degenerative Meniscal Tears?
Meniscal tears are one of the most common injuries to the knee joint. Based on their presentation, meniscal tears are classified as traumatic or non-traumatic (degenerative). Traumatic tears usually occur in younger, active individuals (<40 years) and are caused by an acute traumatic injury, most often while playing sports. Degenerative tears are usually noted in older or middle-aged individuals and often accompany knee osteoarthritis. The risk of meniscal damage increases as the narrowing of the joint space becomes more serious. The medial meniscus is the most torn, and multiple tears are noted in more than one-third of the patients.
Magnetic resonance imaging (MRI) studies indicate a 35% prevalence of degenerative meniscal tears in individuals over 50 years of age. Most of these meniscal tears are asymptomatic in nature (meaning that the individual has no pain or symptoms) and prevalence is similar in those with and without knee pain (20% vs 25%).
Some of the key features of degenerative meniscal tears include:
- They occur in older or middle-aged individuals
- There is no specific incident or injury
- Knee pain that can be hard to pinpoint
- They occur gradually and get worse
Anatomy of the Meniscus
The meniscus is a small, "C" shaped piece of cartilage in the knee joint. Each knee has two menisci, the medial meniscus on the inner aspect of the knee and the lateral meniscus on the outer aspect of the knee. The medial and lateral menisci act as a cushion between the thigh bone (femur) and shin bone (tibia). Functions of the meniscus include:
- Load transmission (spreading weight more evenly into the knee joint)
- Increasing knee joint stability
- Joint lubrication
- Shock absorption
- Nourishes the joint cartilage
Causes of Degenerative Meniscal Tears
Degenerative meniscal tears are intricately connected to tissue aging and are a process in knee osteoarthritis. There is no one cause of degenerative meniscal tears. They are in all likelihood an early manifestation of osteoarthritis, rather than a completely separate diagnosis. Osteoarthritis is a degenerative joint disease that causes breakdown and eventual loss of cartilage in the joint, causing a painful rubbing of bone surfaces with movement.
However, a lot of older and middle-aged individuals have degenerative meniscal tears without knee pain as changes within the menisci are normal age-related changes and responses that occur within the knee as individuals get older. While there is no one cause, there is a range of contributory factors which may increase the risk of developing degenerative meniscal tears such as:
- Poor exercise fitness
- Tightness of the lower limb muscles
- Weakness in the muscles of the thigh and bottom
Signs and Symptoms of Degenerative Meniscal Tears
The principal complaint in symptomatic patients with early degenerative changes is knee joint pain. The pain is connected to certain activities, such as squatting and kneeling and typically improves with rest. The pain can be sensed over the entire knee or limited to a particular area, depending upon which knee compartments are involved. As the degenerative process progresses, the patient may experience further knee symptoms such as a grating sensation (crepitus), early morning joint stiffness, or locking/catching.
Diagnosis of Degenerative Meniscal Tears
Several tests are done clinically to diagnose degenerative meniscal tears, including joint line tenderness, McMurray’s test, and the Thessaly test. However, the diagnostic accuracy of these individual tests for meniscal tears has been poor. Magnetic resonance imaging (MRI) offers great diagnostic accuracy for detecting degenerative meniscal tears, but these tears are also noted in patients with no symptoms. An MRI scan simply establishes the existence of degenerative changes inside the knee (i.e., knee osteoarthritis), but does not impact treatment, and is therefore not recommended. Hence, the ideal way to understand your symptoms is a detailed assessment by your physiotherapist, consultant, or general practitioner.
Treatment for Degenerative Meniscal Tears
Most patients with symptomatic degenerative meniscus tears obtain relief without surgery. Physiotherapy (exercise therapy) is the mainstay of treatment and research data from several studies indicate that about 80% of all meniscus tears will become asymptomatic with appropriate exercise therapy. Medications or steroid injections can be given to relieve pain enough for the patient to participate in exercise therapy.
Physiotherapy is an effective intervention for patients with degenerative meniscal tears and knee symptoms, without the related risks of surgery. A latest high-standard study found that physiotherapy not only provided the same improvement in symptoms as surgery, but also increased thigh muscle strength. Quadriceps muscle weakness is a risk factor for knee osteoarthritis; therefore, physiotherapy may be specifically important for patients with degenerative meniscal tears and no X-ray evidence of considerable arthritic changes. Physiotherapy is therefore suggested as the most suitable treatment for patients with degenerative knee symptoms.
Improvements in function and symptoms are likely to be noticed within 3 months of starting physiotherapy exercises. Continuing with exercise is crucial to sustaining improvements achieved for knee symptoms of a degenerative nature.
Other initial treatments include rest and activity modification, medications, and steroid injections. The order of treatment depends upon the severity of the symptoms and the patient’s preferences.
Surgery is the last resort for a degenerative meniscal tear. While conservative therapy offers some level of relief from symptoms over the long term, these benefits may decline with continued meniscal degeneration. In such individuals, arthroscopic partial meniscectomy (surgical removal of meniscal tissue) can be effective in improving an individual’s quality of life. An in-depth arthroscopic examination of the menisci, joint spaces, and chondral surfaces is crucial to document cartilage health, detect loose bodies, and localize meniscal tears. Partial meniscectomy attempts to debride or clean the unstable degenerative tear with the aim of creating a stable tear or a smooth rim of the remaining meniscus. Your surgeon is tasked to remove the degenerative meniscal tear while simultaneously maintaining as much healthy meniscus as possible.
Surgery is followed by postoperative physiotherapy which is designed to control swelling, restore knee flexion and extension, and improve knee strength.