Description
The medial and lateral menisci are shock absorbers and force distributors between the femur and the tibia. Meniscus takes 40-60% of load on an extended knee joint, which increases up to 90% in flexion. Menisci can tear due to traumatic injury or degenerative wear, which affects force distribution across the knee joint. A tear can occur in the vertical and horizontal planes. Tears may lead to degenerative changes if not already present.
Traumatic meniscal tears most commonly occur in young, active people during twisting sports, such as football, soccer and basketball. Degenerative tears occur commonly in patients with OA. The degree of vascular penetration into the periphery of the meniscus ranges from 10-25% of the meniscal width. Therefore, most areas of the meniscus cannot heal by themselves because they are not vascularized. The presence of a discoid meniscus is also associated with a slightly higher risk of meniscal tears. Medial meniscal tears are more common, however lateral meniscus tears are more common in association with an acute ACL tear.
Different meniscal tear patterns behave differently when subjected to physiological loads. In vertical longitudinal and bucket-handle tear patterns, the hoop/circumferential stresses created by axial loading effectively reduce and compress at its repair site. In radial tear patterns, the disruption of the circumferential collagen fibers within the meniscus allows for distraction across the repair site. Need to consider this when subjecting the repair to stresses during healing.
History
● Rotational forces directed to a flexed knee is the usual mechanism of injury
● A valgus force applied to a flexed knee with the foot planted and the femur externally rotated can result in a lateral meniscus tear
● Varus force applied to the flexed knee when the foot is planted and the femur is internally rotated can result in a tear of the medial meniscus
● Catching, locking, buckling, knee may feel loose
● Knee swelling, usually occurs several hours after the injury (common but not always present)
● Knee pain varies; some may have minimal pain, others describe intermittent pain
● Risk factors: level of activity, knee OA, malalignment of the knee, knee instability
● History of ACL injury may contribute to instability
● Rough or uneven playing surface
● Poor ground or weather conditions
Physical Exam
● May or may not be swollen
● Swelling at the posterior aspect of the knee suggests a popliteal (Baker’s) cyst o Baker’s cysts are associated with meniscal pathology in 80% of cases
● Joint line crepitation and tenderness directly over the joint line is a common finding on palpation ● Joint line tenderness: pain by palpation suggests a meniscal tear
● Bounce home test: o Examiner moves the knee from a flexed position to an extended position o Pain in extended position suggests a meniscal tear o Sensitive but not specific
● McMurray’s test: o Patient is in the supine position with the knee in flexion, examiner flexes the hip and, with one hand on the joint line, rotates the foot internally and externally o Pain with rotation suggests a meniscal tear o Low sensitivity but high specificity
● Apley’s test: o Patient is prone with knee flexed to 90°, place an axial load on the lower leg while rotating the foot o Pain in the affected compartment
● Hyperextension test: o Examiner lifts the heel of the affected leg, hyperextending the knee and adding additional downward force on the tibia o Pain in the affected compartment o Sensitive but not specific
Further Investigations
● MRI is the ideal o Increased signal within the substance of the meniscus and demonstrating conformational changes of the meniscus cartilage o May be useful for identifying associated ligament compromise and articular cartilage changes o Plain film radiographs are indicated in patients with a history of arthritis and chronic longstanding meniscal tears
Classification
● Vertical tears o Longitudinal tear: along the longitudinal axis of the meniscus o Radial tear: transverse to the circumferential fibers of the meniscus o Bucket handle tear: complete longitudinal tear that results in a peripheral and inner fragment
● Horizontal tears o Transverse tear: horizontal axis of the meniscus o Cleavage tear: complete transverse tear that separates the meniscus into superior and inferior fragment
● Parrot’s beak tear: combined, incomplete radial and longitudinal tear, with a displaceable component that resembles a parrot’s beak
● Root tear: tear in the anterior or posterior meniscal roots where the meniscus attaches to the central tibial plateau
● Degenerative tear: result of traumatic or degenerative arthritis
Treatment Options
● Nonoperative care o RICE; reduce pain, minimize swelling and protect the injured tissue o Physical therapy: improve knee joint ROM, core and leg strength and knee stability, normalize gait o Use of crutches or a knee brace may be helpful with painful displaced bucket handle tears o NSAIDs should only be used for short periods because of the negative effects on musculoskeletal healing o Acetaminophen is the preferred drug for reducing pain as it does not interfere with healing process o Small tears (<1 cm) located in the far posterior horns that are asymptomatic do not require operative intervention
● Operative care o If the meniscus tear is large (>1 cm) or is a root tear, or if symptoms persist with non-operative care, arthroscopic surgery should be considered o Meniscal repair should only be used to heal peripheral meniscal lesions affecting healthy meniscal tissue in vascularized areas o Degenerative tears, where the tissue is unhealthy, yellowed, stiff, or filled with chondrocalcinosis deposits, are usually resected via partial meniscectomy o At short- and long-term follow-up, meniscal repair had a higher reoperation rate than partial meniscectomy, however, meniscal repair had a better long-term outcome score and less degeneration o Complete meniscectomy is rarely performed and is usually reserved for cases where the tear is too large or cuts through the entire meniscus
● Post-op care o Focuses on limiting axial load and rotational movement for the first month o Followed by ROM and strengthening exercises o Immediate post-op care for the partial meniscectomy: icing and elevation throughout day and night, use crutches for 1 st week and progress to weight-bearing as tolerated o Post-op measures are similar after a meniscus repair, however, weight-bearing is approached more cautiously and full weight-bearing should be delayed for at least 4-6 weeks after surgery, as well as limiting knee ROM especially in full flexion o Need for brace is usually not indicated after meniscectomy, but depends on the patient activity and condition of repair after a meniscal repair
● After partial meniscectomy, resection leads to rapid recovery over the course of a few weeks
● After meniscus repair, healing of the torn meniscus usually takes 4-6 months
● There is currently no consensus on optimal amount of weight-bearing and ROM during the post-op period after meniscal repair o With the exception of restriction of weight-bearing and ROM, if restricting one or the other, clinical success rates range from 62-100% across all study groups. o No discernable benefit identified when comparing restrictions in ROM, weight-bearing or dual restriction o The accelerated rehab group may have avoided some detrimental effects from periods of prolonged immobilization (strength and muscle volume)
References
1. BMJ Best Practice 2. Fox et al. The human meniscus: a review of anatomy, function, injury, and advances in treatment. Clin Anat. 2015 Mar;28(2):269-87. 3. O’Donnell et al. Rehabilitation protocols after isolated meniscal repair: a systematic review. Am J Sports Med. 2017 Jun;45(7):1687-1697.
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Dr. Mike Hadbavny
Victoria Sports Chiropractor FRCCSS(C)
If you are interested in learning more about how chiropractic care can be effective for your particular condition or health goals, contact Dr. Mike Hadbavny at 250-881-7881 today to make an appointment and discover the many benefits of seeing a chiropractor in Victoria BC. Contact us today.