- Menisci are wedge-shaped fibrocartilaginous structures found in the knee joint.
- They cover the articular surface of the tibial plateau.
- They are essential for the normal function of the knee:
- Absorb shock
- Distribute load
- Increase stability
- Provide lubrication
- In younger patients, tears are generally acute traumatic injuries (e.g., sports injuries, occupational injuries).
- In older patient, tears are more commonly degenerative (accompanied by degenerative osteoarthritis).
- Exact incidence is unknown, but meniscus tear is a fairly common injury, especially with sports activities.
- Tears of the medial meniscus are more common (because of attachment to the medial collateral ligament).
- Anterior cruciate ligament (ACL) tears often have an associated medial meniscus tear.
- Men are at increased risk compared to women.
- Bimodal distribution:
- Common in younger men: associated with athletic injuries
- Common in older adults: associated with degenerative changes of the meniscus
- Rotational or shearing forces placed across the tibiofemoral joint (activities that require sudden changes in direction and speed)
- Direct trauma to the knee (often with concomitant knee ligament injury)
- Low-energy injuries in patients over 40 years of age, often with related degenerative changes (osteoarthritis)
Types of meniscal tears
There are several types of tear patterns in meniscal tears:
- C-shaped wedges of fibrocartilage between the distal femur and proximal tibia:
- The medial meniscus is semilunar in shape.
- The lateral meniscus is more circular in shape.
- 70% type I collagen
- Several ligaments and the joint capsule attach to the meniscus in order to improve stability.
- Blood supply is peripheral:
- A peripheral tear has greater blood supply and more potential to heal.
- A center-portion tear is relatively avascular, with a poor potential to heal.
Traumatic mechanisms for tears:
- Rotational or shearing forces placed across the tibiofemoral joint, seen in activities such as:
- Lifting heavy weights
- Military-related activities
- Sports (soccer, rugby, football, basketball, baseball, skiing, and wrestling)
- Direct trauma to the knee with concomitant knee ligament injury
- Low-energy injuries in older patient with underlying degenerative changes of the meniscus
- Often a challenging diagnosis with variable symptoms
- Patients are often able to continue to participate in the initial activity.
- Assess mechanism of injury:
- Direct trauma
- Patients often report hearing a pop at the time of injury followed by localized pain.
- Mechanical symptoms are common:
- Sensation of giving way
- Severity of symptoms often related to type of meniscal tear:
- A bucket-handle tear may cause significant locking and associated pain.
- A small vertical tear may cause only intermittent vague symptoms.
- Joint effusion may develop over a few hours (more quickly with other associated injuries).
- Antalgic gait
- Inability to squat
- Effusion (occurs more rapidly with peripheral tears; may take up to 24 hours to demonstrate an effusion)
- Joint line tenderness
- Evaluate for effusion: fluid shift test
- Range of motion (ROM): Does the patient have full flexion and extension?
- Ligamentous stability:
- Cruciate ligaments:
- Anterior/posterior drawer
- Lachman test
- Collateral ligaments:
- Varus stress test
- Valgus stress test
- Cruciate ligaments:
- Meniscal tests: Multiple tests have been described, with variable sensitivity and specificity:
- Thessaly test:
- The patient is weight-bearing (flat-footed) on 1 leg flexed at 20 degrees and asked to initiate internal and external rotation.
- A positive test is joint line discomfort or complaints of locking or catching.
- McMurray test:
- The patient is supine, and the knee is taken through its ROM with an associated varus or valgus force with internal and external rotation of the foot.
- A positive test includes popping or clicking of the knee with associated pain.
- Bounce home test:
- The patient is supine, and their heel is supported while the examiner passively flexes the knee. The knee is then passively allowed to extend under the influence of gravity.
- The knee should normally extend fully, or “bounce home,” with a sharp end feel.
- Positive if incomplete extension of the knee or has a rubbery end feel
- Childress test:
- The patient squats and duckwalks.
- The test is positive if there is incomplete flexion limited by pain or clicking is heard.
- Apley compression and distraction test:
- The patient is prone, with the knee flexed to 90 degrees.
- The examiner internally and externally rotates the tibia while applying compression then distraction.
- Positive for ligament injury if rotation plus distraction is more painful or increased rotation compared to normal side
- Positive for meniscal injury if rotation plus compression is more painful or decreased rotation compared to normal side
- Thessaly test:
Diagnosis is usually suspected with a thorough history and physical examination, and often confirmed with diagnostic imaging (e.g., MRI) or by direct visualization (e.g., arthroscopy).
- Only indicated if evaluating for other possible diagnoses:
- Rheumatological disease
- Arthrocentesis generally not indicated:
- May be indicated in the evaluation for other diagnoses
- May provide symptomatic relief when there is a large effusion
- Indicated to evaluate for associated acute bony injury or underlying OA changes
- Anteroposterior (AP), lateral, oblique, sunrise, and weight-bearing projections of the knee are ideal.
- Safe and inexpensive
- Able to visualize peripheral meniscus tears
- Limited ability to visualize deep structures of the knee
- Imaging modality of choice for diagnosis and characterization of meniscal tears
- Accuracy greater than 90%
- Not always indicated prior to arthroscopy: may give additional information regarding injuries to associated ligaments and cartilage
- Gold standard for diagnosis of a meniscal tear
- Provides direct visualization of the meniscus and other associated tissues
- A diagnostic arthroscopy can be converted to therapeutic arthroscopy if pathologic findings are present.
Management of meniscal tears is dependent on the type of tear, age of the patient, occupation of the patient, associated mechanical symptoms, and other associated injuries (e.g., ACL tear).
- Younger patients with unstable, painful meniscal tears or associated mechanical symptoms will benefit from arthroscopic surgical management.
- Older patients with degenerative meniscal tears may benefit from an initial trial of physical therapy (PT).
- Factors indicating arthroscopy intervention:
- Loss of motion or a “locked” knee
- Associated ligamentous injury (e.g., ACL tear)
- Lack of improvement with conservative care
Conservative management indicated as initial treatment in degenerative tears in older patients or prior to arthroscopy in younger patients:
- Rest, ice, compression, and elevation (RICE)
- Oral analgesics as needed
- Bracing, knee sleeves, and crutches may be used briefly for symptomatic relief.
- Begin with ROM, quadriceps strengthening
- Advance based on symptoms
- Cross-training for specific exercise if appropriate (e.g., swimming, biking)
- Arthroscopy indications:
- Mechanical symptoms
- Persistent pain and effusion
- Associated ligamentous injuries
- Lack of response to initial conservative management
- Arthroscopy is used diagnostically and therapeutically.
- Meniscal repair preferred over partial meniscectomy:
- For large tears
- Meniscal tears in younger patients
- Total meniscectomy has been shown to accelerate osteoarthritis and is avoided.
- Meniscal transplantation with a cadaveric allograft is occasionally used in younger patients with significant meniscal trauma.
- Rehabilitation depends on:
- Age of patient
- Occupational/sports involvement
- Type of meniscal injury
- Type of management of the meniscal tear (conservative vs. surgical)
- Goals of rehabilitation:
- Progressive ROM
- Aerobic conditioning and strength training
- Return to normal activity levels
- Rehabilitation after meniscal repair or meniscus transplant is similar, except for restrictions on ROM and weight-bearing status.
- Recurrent meniscal injury seen with both surgical and nonsurgical management
- Premature osteoarthritis secondary to meniscus loss
Long-term outcomes depend on:
- Type of tear
- Type of repair
- Amount of meniscus removed during surgical procedures
- Age of patient
- Underlying condition of the knee
- Iliotibial band syndrome: cause of lateral knee pain, attributed to the repetitive friction between the iliotibial band and the lateral femoral condyle (overuse injury). Iliotibial band syndrome is frequently seen in athletes and military personnel. Diagnosis is clinical. Conservative treatment includes RICE and PT. Corticosteroid injections may be utilized in refractory cases.
- Knee osteochondritis dissecans (OCD): an orthopedic disorder characterized by the detachment of a segment of subchondral bone and cartilage due to focal aseptic necrosis. The disorder may occur at any age, but it is most commonly seen in adolescents who participate in competitive sports. Diagnosis is by X-ray. Conservative treatment includes RICE and PT. Arthroscopic intervention may be required in refractory cases.
- Lumbosacral radiculopathy: pain caused by lumbar nerve root irritation or compression. Lumbosacral radiculopathy is commonly attributed to disc herniation, vertebral degeneration, and neuroforaminal narrowing. Presentation includes low back pain with dermatomal radiation to lower limbs, accompanied by paresthesias, myotomal muscle weakness, and hyporeflexia. Diagnosis is clinical and confirmed by MRI. Conservative treatment includes RICE and PT. Refractory cases may require epidural steroid injection or surgical decompression.
- Anterior and posterior cruciate ligament injury: anterior cruciate ligament (ACL) injuries occur most frequently secondary to non-contact, deceleration injuries, and they are also seen in contact sports secondary to trauma. Posterior cruciate injuries are seen in contact sports and high-energy trauma such as motor vehicle accidents. Both injuries may have associated meniscal trauma.
- Patellofemoral pain syndrome: the presence of vague anterior knee pain, generally without any structural changes in the articular cartilage that would be considered pathological. Patellofemoral pain syndrome may be considered in a patient with meniscal symptoms.
- Tibia and fibula fractures: intra-articular fractures of the distal femur or proximal tibia may have associated meniscal injuries.
- Osteoarthritis: the most common form of arthritis. Osteoarthritis is due to cartilage destruction and changes of the subchondral bone in weight-bearing joints. The risk of developing this disorder increases with age, obesity, and trauma. Degenerative changes are also commonly present, and meniscal injuries predispose the patient for the development of premature osteoarthritis.
- Lafferty, PM, & Cole, PA. (2020). In Browner, BD, et al. (Eds.), Tibial Plateau Fractures. pp. 2181–2276. https://pubmed.ncbi.nlm.nih.gov/29261932/
- Hansen, JT. (2019). Lower limb. In Netter’s Clinical Anatomy. pp. 291–366. https://www.worldcat.org/title/netters-clinical-anatomy/oclc/1017817783
- Raj, MA, & Bubnis, MA. (2021). Knee meniscal tears. StatPearls. Treasure Island (FL): StatPearls Publishing. http://www.ncbi.nlm.nih.gov/books/NBK431067/
- Dennis, A, et al. (2021). Meniscal injury of the knee. UpToDate. Retrieved July 16, 2021, from https://www.uptodate.com/contents/meniscal-injury-of-the-knee
- Lento, P, Marshall, B, & Akuthota, V. (2020). Chapter 72: Meniscal injuries. In Frontera, W.R., et al. (Eds.). pp. 403–409. Elsevier.