The menisci (plural) are vital to normal, painless knee function as well as to the nutrition and health of the underlying articular cartilage. The meniscus has multiple roles, the 2 primary functions are 1) increase the contact surface area and 2) contribute to the stability of the knee. Damage or interruption of the integrity of the meniscus may diminish its function. As a rule, degree of functional loss corresponds to the amount of meniscus that is damaged or resected.
Treatment options for a damaged, or “torn” meniscus generally falls into 3 categories
Loss of small parts of the meniscus (< 20%) is thought to have minimal effects on the overall meniscal function. Larger loss of substance can have long-term joint mechanical effects due to increased cartilage stress and subtle instability.
Tears of the meniscus, if treated or untreated, can lead to significant knee arthrosis. Postmeniscectomy patients are also subject to increased risks for arthrosis, and that probability increases in ACL-deficient knees.
It is preferable to retain as much meniscal substance as possible.
Meniscal tears in the periphery have an adequate blood supply and are amenable to primarily repair. Complex tears and tears in the central, avascular zone are not amenable to repair. Currently, total and even partial meniscectomy is commonly performed for these complex tears, and degenerative arthrosis is commonly seen.
There are multiple tear patterns of the meniscus, which have surgical implications. Of the more important considerations for meniscal treat is whether the tear repairable or resectable. Conditions that favor repairable tears are
- Age under 40 years old
- Peripheral tears
- Traumatic (rather than degenerative) tears
Multiple studies have reported on the negative long-term effects of a meniscectomy. In a 12 year follow up study in those over 40 years old, Jones et al (1978) reported up to 75% of patients having knee pain with evidence of joint space narrowing and varus angulation (5.3 degrees). Jaurequito et al (1995) reported on 26 patients 8 years following lateral meniscectomy. Excellent or good results decreased from 92% at the time of maximal improvement to 62% at the most recent follow-up. Eighty-five percent of patients were initially able to return to their preinjury activity level; however, only 48% were able to maintain this level of activity at the most recent follow-up.
A contrasting result was reported by Hiroshi, et al (2000). Sixty-seven patients were evaluated retrospectively with an average of 12.2 years follow-up. Seventy-nine percent of the patients had a satisfactory outcome in terms of function. The amount of meniscus removed and the degree of radiographic arthritis at the time of the meniscectomy were determining factors for long-term functional results. Osteoarthritic deterioration was seen in 48% of patients after the surgery, but radiographic deterioration after arthroscopic partial meniscectomy was mild on long-term follow-up. Age, gender, and the degree of cartilage degeneration at the time of operation, in contrast, showed no significant association. They concluded that arthroscopic partial meniscectomy for isolated meniscal injury yields favorable functional results, however half of patients will show radiographic osteoarthritic changes in the long-term.
The author of this section believes that partial meniscectomy in an otherwise normal knee with normal alignment will do well in those over 40 years old, but will likely have long term degenerative effects in the younger patient. A partial meniscectomy in an abnormal knee (i.e., ACL deficient knee, malaligned knee, pre-existing articular cartilage damage) will likely have significant degenerative advancement in the mid or long term.