Osteoarthritis Singled Out as Cause of Meniscal Damage and Knee Pain

BOSTON, Nov. 29 -- In older patients, osteoarthritis causes both knee pain and damage to the meniscus, according to researchers here.
Action Points
Explain to patients that knee stiffness and pain in older individuals are probably caused by osteoarthritis rather than by damage to the meniscus.
Explain that meniscus damage may also be caused by osteoarthritis.
Meniscal damage is not directly linked to knee pain, aching, and stiffness but, rather, both are related to osteoarthritis, Martin Englund, M.D., Ph.D., of Boston University, and colleagues reported in the December issue of Arthritis & Rheumatism.
In the U.S., 11% to 15% of men and women 65 and older have osteoarthritis of the knee manifesting in pain, aching, and stiffness.
Associated with aging, obesity, and sport injuries, tears to the menisci are a common MRI finding, especially in an osteoarthritic knee. However, whether meniscal damage foreshadows knee pain from another source or directly causes it has not been known, the researchers said.
To help improve the early detection of osteoarthritis, researchers with the Multicenter Osteoarthritis Study set out to evaluate the effect of meniscal damage on the development of knee pain, aching, and stiffness in a randomized prospective study of 3,026 individuals ages 50 to 79 who had a high risk of developing osteoarthritis of the knee.
Participants included men and women and white and ethnic minorities recruited from Alabama and Iowa. Knees were studied at baseline and at 15 months.
Case knees (110) were drawn randomly from patients with no frequent symptoms on most days at baseline but who developed frequent pain and stiffness in one or both knees at 15 months.
Control knees (220) were drawn randomly from patients with no frequent symptoms at baseline or at 15 months.
After MRI studies at baseline and 15 months, two musculoskeletal radiologists blinded to the individuals' status assessed meniscal damage using the following scale: 0=intact, 1=minor tear, 2=nondisplaced tear or prior surgical repair, and 3=displaced tear, resection, maceration, or destruction.
Finally, the effect of meniscal damage on the development of frequent knee pain was studied with contingency table and logistic regression analysis.
At baseline, meniscal damage was common in both case knees (38%) and in control knees (29%), with a higher frequency among women.
There was a modest association between the meniscal damage score (range 0-3) and the development of frequent knee pain, aching, or stiffness (odds ratio: 1.21, 95% CI: 0.96 to 1.51), adjusted for age, sex, and body mass index.
However, meniscal damage was present mostly in knees with radiographic evidence of osteoarthritis as measured by Kellgren/Lawrence grade.
For K/L grade 3 or greater, meniscal damage was present in 82%, for grade K/L grade 2, in 39%, and for grade 1, in 26%. Osteoarthritis was considered to be present for grade 2 or greater.
In a stratified analysis, the researchers found no independent association between meniscal damage and the development of frequent knee symptoms.
Meniscal damage in older adults is highly associated with osteoarthritis of the knee, Dr. Englund wrote. However, he added, meniscal damage often seems not to be directly responsible for later pain and stiffness symptoms. Other features of osteoarthritis may be responsible.
It is conceivable, he said, that certain types of meniscal lesion may be directly responsible for knee pain, particularly during the early stages of certain types of tears. Still, he noted, the high prevalence of meniscal damage in the older adult knee and the weak association with knee symptoms suggest that any such discomfort may be self-limited and can be treated conservatively.
The study had certain important limitations, the investigators said, including its limited sample size and the need to collapse various types of meniscal damage into a few categories for statistical analysis.
Also, they said, the relationship between site of damage or type of lesion and knee symptoms requires further study.
Stressing the importance of treating osteoarthritis as a whole-joint disorder, Dr. England said that this study calls attention to the risk of misinterpreting meniscal damage as the direct cause of knee pain.
However, he added, basic prevalence data of meniscal lesions and their association with knee symptoms in the general population of older adults remain to be explained.
This study was supported by grants from the National Institute on Aging. Dr. Englund's work was supported by the Arthritis Foundation.
Primary source: Arthritis & RheumatismSource reference: Englund M, et al "Effect of meniscal damage on the development of frequent knee pain, aching, or stiffness" Arthritis & Rheumatism 2007; 56: 4048-4054.