Recently a friend of mine underwent a meniscectomy and post-operatively inquired what the meniscus actually did, how it typically was injured and what she should expect during the rehabilitation process. Below is an in-depth look at the information I provided for her.
Anatomical considerations: The meniscus is an important load-bearing structure that supports 70% of the load transmitted through the lateral compartment and 50% medially, thus decreasing contact pressures on the articular cartilage. It is also an important secondary stabilizer of the knee, resisting anterior translation. The meniscus has nutritive as well as lubricating properties in the knee joint as well. The medial meniscus is C shaped and thicker posteriorly. The lateral meniscus is O shaped and of equal thickness throughout. The red zone or fibrous outer portion of the meniscus is vascular and therefore tears here will often heal. The inner 2/3rds or white cartilaginous zone of the meniscus does not have a good blood supply and therefore, tears are less likely to heal in this area.
Pathogenesis: The meniscus is most commonly injured by a compressive or weight bearing force, combined with tibiofemoral rotation in the transverse plane as the knee moves from flexion to extension. A tear may therefore occur during activities which require rapid cutting or pivoting.
Epidemiology: The posterior medial meniscus is the most commonly injured portion of the menisci, secondary to it being less mobile and therefore greater stresses occurring in this area. Athletes/younger population most often obtain meniscus tears via non-contact activities like rapid cutting, pivoting or deceleration movements. With increasing age, tears can often occur with trivial injury due to degeneration of the meniscus.
– injury followed by pain in area of medial or lateral joint lines
– most patients describe pain especially when the knee is straightened.
– Following an injury, the knee may click, lock or feel weak
– MRI may help to confirm the diagnosis
Nonoperative vs operative management:
The overall treatment goal is to preserve as much meniscal tissue as possible while addressing the clinical symptoms caused by the meniscal tear.
Nonoperative treatment which consists of anti-inflammatory medications and careful strengthening exercises may allow for the menisci to heal, especially if the tear lies in the outer third of the structure. This treatment may take 6-8 weeks in order for meniscal healing to occur. If the patient continues to complain of symptoms following 6 weeks, arthroscopic meniscectomy may be considered.
Both complete and partial meniscectomies result in a significant increase in the load across the joint and on the articular cartilage and reduce the shock absorption capacity of the knee. A partial meniscectomy leaves a rim of tissue in place, which maintains some stress protection for the articular cartilage, in contrast to a total meniscectomy, which (in the absence of regeneration) is associated with increased cartilage degeneration, joint narrowing, alterations in bone geometry, and osteophyte formation. Due to these factors, many surgeons choose to preserve the meniscus with a meniscal repair or in some cases reconstruction with an allograft.
In addition to the location of the tear, the pattern of the tear may also indicate if surgery may be required. Longitudinal tears have a favorable healing potential except for a bucket-handle tear (a variant of a longitudinal tear) in which circumferential fibers are involved. Radial or flap meniscus tears also involve the circumferential fibers. These tears are more easily managed with debridement/ meniscectomy. Degenerative tears also respond better to meniscectomy than repair.
Although meniscectomy was originally performed by open arthrotomy, the procedure is almost universally done today by arthroscopic means. Partial meniscectomy is indicated in unstable tears which are not repairable due to location or configuration and serves to preserve as much of the normal meniscus as possible. In this procedure, the surgeon removes only the damaged or unstable portion of the meniscus, and balances the residual meniscal rim. The procedure for a total meniscectomy, the entire meniscus may be removed.
Pre operative rehab for a meniscal injury that is to undergo a meniscectomy may involve:
– Edema/pain control
– Maintaining full ROM
– Regaining/maintaining quadriceps strength
Rehab following a partial medial or lateral meniscectomy can usually progress as tolerated, with no contraindications or limitations due to there being no anatomic structure that must be protected. Goals are early control of pain and edema, immediate weight bearing, obtaining and maintaining full ROM and regaining proper quadriceps strength.
Always consult with your PCP or Surgeon.
Information gathered from USC powerpoint slides