The meniscus is a C-shaped piece of tough, rubbery cartilage that acts as a shock absorber between your shinbone and thighbone. It can be torn if you suddenly twist your knee while bearing weight on it. A posterior horn tear is the most common. The meniscus is broken down into the outer, middle, and inner thirds. The third in which the tear is located will determine the ability of the tear to heal since the blood supply in that area is critical to the healing process. The meniscus is a piece of cartilage that provides a cushion between your femur (thighbone) and tibia (shinbone). There are two menisci in each knee joint. They can be damaged or torn during activities that put pressure on or rotate the knee joint.
The meniscus cartilage itself is made up of softer fibrocartilage. The knee has two C-shaped meniscus structures made of softer fibrocartilage. These structures are anchored to the tibia by the peripheral capsular attachments of the menisci, which allow them more mobility within the joint
The menisci are internal structures that are of central importance for a healthy knee joint; they have a key role in the structural progression of knee osteoarthritis (OA), and the risk of the disease dramatically increases if they are damaged by injury or degenerative processes. Most commonly, meniscal tears are caused by some sort of traumatic injury or sports injury. An unnatural over-rotation of the leg can cause the cartilage of either of the menisci to tear either fully or partially. Diagnosing a knee injury or problem includes a medical examination and usually the use of a diagnostic procedure(s) such as an x-ray, MRI, CT scan, or arthroscopy. Both non-operative and surgical treatment options are available to treat knee pain and problems depending on the type and severity of the condition.
Other Names
- Medial meniscus tear
- Lateral meniscus tear
- Meniscus tear
- Meniscus repair
- Bucket handle meniscus tear
Pathophysiology
- Medial meniscus
- More common than lateral
- Posterior horn in degenerative tears
- Lateral meniscus
- Commonly seen with ACL injuries
Causes
-
- Most often due to a twisting motion on the partially flexed, weight-bearing knee
- May also occur as part of more major, combined injuries to the knee
- Chronic
- Degenerative process in older individuals
- Acute
- Osteochondral Defect
- Multiligament Knee Injury
- ACL Injury
- PCL Injury
- MCL Injury
- LCL Injury
- Posterolateral Corner Injury
- Bone contusion, less commonly fracture
- Chronic
- Knee Osteoarthritis
- Up to 75% of patients with knee OA have a meniscal injury[6]
- Knee Osteoarthritis
- Medial Meniscus & Lateral Meniscus
- Crescent-shaped wedges of fibrocartilage oriented circumferentially
- Positioned between the tibia and the femur in the medial and lateral compartments
- Function
- Load transmission
- Shock absorption
- Stability
- Congruence
- Lubrication
- Proprioception
- Male > Female
- Up to 80% of cases reported in men[7]
- Orthopedic
- ACL Insufficiency
- Fractures
- Distal Femur Fracture
- Patellar Fracture
- Tibial Plateau Fracture
- Dislocations & Subluxations
- Patellar Dislocation (and subluxation)
- Knee Dislocation
- Proximal Tibiofibular Joint Dislocation
- Muscle and Tendon Injuries
- Quadriceps Contusion
- Iliotibial Band Syndrome
- Quadriceps Tendonitis
- Patellar Tendonitis
- Popliteus Tendinopathy
- Extensor Mechanism Injury
- Patellar Tendon Rupture
- Quadriceps Tendon Rupture
- Patellar Fracture
- Ligament Pathology
- ACL Injury
- PCL Injury
- MCL Injury
- LCL Injury
- Meniscal Pathology
- Posterolateral Corner Injury
- Multiligament Injury
- Arthropathies
- Knee Osteoarthritis
- Septic Arthritis
- Gout
- Bursopathies
- Prepatellar Bursitis
- Pes Anserine Bursitis
- MCL Bursitis
- Infrapatellar Bursitis
- Patellofemoral Pain Syndrome (PFPS)/ Anterior Knee Pain)
- Chondromalacia Patellae
- Patellofemoral Osteoarthritis
- Osteochondral Defect Knee
- Plica Syndrome
- Infrapatellar Fat Pad Impingement
- Patellar Instability
- Neuropathies
- Saphenous Nerve Entrapment
- Other
- Bakers Cyst
- Patellar Contusion
- Pediatric Considerations
- Patellar Apophysitis (Sinding-Larsen-Johnansson Disease)
- Patellar Pole Avulsion Fracture
- Tibial Tubercle Avulsion Fracture
- Tibial Tuberosity Apophysitis (Osgood Schalatters Disease)
Symptoms
- Knee pain.
- Swelling.
- Heat.
- Redness.
- Tenderness.
- Difficulty bending the knee.
- Problems weight-bearing.
- Clicking or popping sounds.
Diagnosis
- History
- In acute setting, may have description of sudden twisting or turning motion
- Degenerative or subacute injuries often have no clear mechanism
- Pain location is usually on the affected side of the joint
- Often also endorse swelling, clicking, giving way
- Swelling may wax and wane
- In bucket handle tears, locking or getting stuck can occur
- Pain waking patients up from sleeping is common
- Physical Exam: Physical Exam Knee
- The effusion may or may not be present
- Gait is often antalgic
- Tenderness along the joint line is considered the most sensitive exam finding (need citation)
- Special Tests
- McMurray’s Test: Passively flex and extend the knee in medial and lateral rotation
- Apley Grind Test: Prone, affected knee flexed to 90°, medial and lateral rotation with compression
- Thessaly Test: Standing, knee bent 20-30°, rotate knee medial and laterally
- Bounce Home Test: Flex knee then passively bring back into extension
Radiographs
- Standard Radiographs Knee
- Acute
- Often normal
- The effusion may be seen on the lateral view
- Chronic
- Joint space narrowing
- Calcifications may be seen (e.g. CPPD)
MRI
- Findings
- The increased signal within the meniscus
- Bucket handle tear
- Flipped meniscus
- Double PCL or double anterior horn sign
- Parameniscal Cyst
- Suggests meniscus tear
- Diagnostic accuracy (need citation)
- Sensitivity: 93%
- Specificity: 88%
- High false positive rate
CT
Arthroscopy
- Gold standard[8]
- Not routinely performed unless unable to obtain an MRI
Classification
- Location
- Red zone (outer 1/3, vascularized)
- Red/white zone (middle 1/3)
- White zone (inner 1/3, avascular)
- Position
- Anterior
- Middle
- Posterior third
- Root
- Size
- Small < 5 mm
- Large > 5 mm
- Pattern[9]
- Vertical/longitudinal: common, associated with ACL tear
- Bucket handle: vertical, fragment may displace into the notch
- Oblique/flap/parrot beak: may cause mechanical locking symptoms
- Radial
- Horizontal: older population, associated with meniscal cyst
- Complex
- Root: functionally equivalent to a total meniscectomy
- Lateral root tears associated with ACL tears
- Medial root tears associated with chondral injuries
Treatment
- Quadriceps setting.
- Mini-squats.
- Straight leg raise.
- Hamstring heel digs.
- Leg extensions.
- Standing heel raises.
- Clams.
- Hamstring curls.
Prognosis
- Historically, in 1970s, meniscectomy was the gold standard
- Associated with increased risk of joint space narrowing, degenerative joint disease and osteoarthritis
- Modern management is centered around preservation, repair, and reconstruction of the meniscus
- Factors that help determine management
- Age (old vs young)
- Activity level
- Comorbidities
- Degree of symptoms
- Physical exam
- Likelihood meniscus is the cause of pain
- Type and location of tear
- An arthroscopic partial meniscectomy (APM)
- Sihvonen et al: No better than sham arthroscopy[10]
- Arthroscopic meniscus repair
- Lee et al: 90.6% success rate for repair at 2.3 years, 71.4% at 6.6 years[11]
- Nepple et al systematic review: at 5 years, failure rates ranged from 22.3% to 24.3%[12]
- Meniscus Repair[13]
- Among 6 studies looking at the return to sport among isolated meniscus repair
- Time to return ranged from 4.3 months to 6.7 months
- 81 to 100% were able to return to sport
- Meniscal allografting
- Bin et al: 10-year follow-up survival was roughly 89.2%[14]
Nonoperative
- Indications
- Chronic degenerative changes in elderly patients
- Patients who are not good surgical candidates
- Peripheral meniscus tear in red/red zone (peripheral 25-30%)[15]
- Tears < 5 mm
- Rest
- NSAIDS
- Physical Therapy
- Corticosteroid Injection
Operative
- Indications
- Young, active individuals
- Centrally located tears
- Large tears
- Surgical options
- Arthroscopic partial meniscectomy (APM)
- Arthroscopic Meniscus repair
- Goals: achieve meniscal healing, avoid adverse effects of partial and total meniscectomy
- Meniscal allograft or transplant
- Meniscal scaffolds
- Partial meniscal substitute
- Designed to re-establish load distribution across the knee joint, providing chondroprotection
Legg Calve Perthes Disease
