Meniscal Tears
The lateral and medial meniscus are crescent-shaped fibrocartilage structures that collectively cover around 70% of the articular surface of the tibial plateau. Its primary function is to transfer forces across the knee, with secondary stabilising mechanisms. Knee Meniscal Tears – StatPearls – NCBI Bookshelf.
The meniscus is prone to injury from both traumatic and degenerative causes. In the young knee, a torsional force with axial load is the most common mechanism of injury, which may or may not be associated with concurrent Anterior Cruciate Ligament (ACL) injury and/or bony lesions. In the older patient, meniscal tears often go hand in hand with developing arthrosis. The mechanisms of injury is substantially less in these patients, with symptoms classically starting when simply standing from a seated position or climbing a set of stairs. The prevalence of symptomatic meniscal tears approximately affects 60-70 patients per 100,000 annually, with the medial meniscus more commonly affected by Meniscal tears – PMC.
Meniscal tears are categorised on MRI by both their shape, location, and whether or not there is displacement. More information can be found here Knee Meniscal Tears – StatPearls – NCBI Bookshelf about how these tears are categorised. Tears located in the outer periphery have the best possible chance of healing, with central tears being less likely to repair naturally or even surgically due to their avascular nature Knee Meniscal Tears – StatPearls – NCBI Bookshelf.
What are the signs and symptoms?
In the traumatic young patient’s knee, there is a single episode of injury often with an inability to continue to play or exercise. There is often concurrent swelling to the knee that may appear immediately or over the next 24-48 hours. Immediate joint swelling is typically indicative of a haemarthrosis (bleed into the joint) and is associated with ACL injuries, less commonly intraarticular fractures (lipohaemarthrosis). The acute swollen knee: diagnosis and management – PMC. Swelling that develops more over a period of days is more suspecting of an isolated meniscal tear.
These injuries may be associated with mechanical symptoms. These include locking, where the patient is unable to fully straighten their knee as a torn piece of meniscus has become caught between the femoral condyle and tibial plateau, or instability, where the patient is unable to trust their knee in concurrent ACL tears.
In the older knee, there is often not that history of trauma. Degenerative meniscal tears are significantly less likely to cause mechanical symptoms, and their prevalence in the asymptomatic population is very high. Prevalence of abnormal findings in 230 knees of asymptomatic adults using 3.0 T MRI – PMC.
Clinically, patients typically complain of medial joint line pain. McMurray’s and Apley’s compression tests are often symptomatic and sensitive tests, especially in the younger patient. Evaluation of the Diagnostic Accuracy of Clinical Examination for Diagnosing Medial Meniscal Injuries Using Arthroscopy – PubMed. The knee will be stable unless there is concurrent injury to the ACL and/or MCL on Lachman’s and valgus testing, respectively.
How is it diagnosed?
The diagnosis will be made from a combination of your clinical history, examination findings (please see above) and, in necessary cases, an MRI scan.
MRI investigations are typically reserved for traumatic cases in the younger patient or in those patients with ‘mechanical symptoms’ where surgical workup is being considered. For older patients without mechanical symptoms, often a plain film X-ray will suffice to ascertain the level of OA, as it is significantly less likely that a meniscal tear in this cohort of patients would be treated surgically in isolation.
How is it treated?
Treatment options are divided into conservative and surgical.
Conservative options:
- For appropriate patients, oral analgesia in combination with a period of unloading. Can help settle symptoms down. We know that many degenerative meniscal tears will settle down by themselves without any invasive procedures. Prevalence of abnormal findings in 230 knees of asymptomatic adults using 3.0 T MRI – PMC .
- Physiotherapy can be helpful in maintaining knee mobility and strengthening the surrounding musculature to reduce knee symptoms in patients with degenerative meniscal tears A Randomized Trial of Physical Therapy for Meniscal Tear and Knee Pain – PubMed.
- In refractory or persisting cases, an ultrasound-guided local anaesthetic and steroid injection +/- joint aspiration (removing any fluid from the joint) can be helpful at easing any associated inflammation that may be persisting. Usually again utilised for the degenerative tears Survivorship and outcomes of intra- and perimeniscal corticosteroids injections with structured physiotherapy for degenerative medial meniscus tears – PubMed but can also be helpful in the young population in carefully selected patients that have not improved with other conservative options.
Surgical options:
Surgery for symptomatic meniscal tears is usually reserved for those with ‘mechanical symptoms’, the younger traumatic knee patients or those that have failed conservative options, especially in the case of the degenerative meniscal tears.
- In the younger patients with a large symptomatic meniscal tear with mechanical symptoms with no signs of joint osteoarthritis, arthroscopy has a clear role and involves meniscectomy (cutting out) or, where possible, a meniscal repair. Repair is often preferred for these patients, as it better preserves knee biomechanics and lower long-term osteoarthritis risks. Arthroscopic Meniscectomy vs Meniscal Repair: Comparison of Clinical Outcomes – PubMed
- Special note should be made for a specific type of meniscal tear termed a ‘meniscal root attachment tear’. These are usually treated surgically even in the absence of mechanical symptoms due to the strong association with developing early-onset osteoarthritis if left untreated. Medial Meniscus Root Tears: Anatomy, Repair Options, and Outcomes – PubMed
Finally, for degenerative meniscal tears, arthroscopy may be considered if conservative options have not helped, but evidence shows less favourable and consistent outcomes, especially in the presence of developing knee osteoarthritis. Effect of Physical Therapy vs Arthroscopic Partial Meniscectomy in People With Degenerative Meniscal Tears: Five-Year Follow-up of the ESCAPE Randomized Clinical Trial – PubMed
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