Relationship between knee and ankle degeneration in a population of organ donors

Abstract

Background: Osteoarthritis (OA) is a progressive degenerative condition of synovial joints in response to both internal and external factors. The relationship of OA in one joint of an extremity to another joint within the same extremity, or between extremities, has been a topic of interest in reference to the etiology and/or progression of the disease.

Methods: The prevalence of articular cartilage lesions and osteophytes, characteristic of OA, was evaluated through visual inspection and grading in 1060 adult knee/tali pairs from 545 cadaveric joint donors.

Results: Joint degeneration increased more rapidly with age for the knee joint, and significantly more knee joints displayed more severe degeneration than ankle joints from as early as the third decade. Women displayed more severe knee degeneration than did men. Severe ankle degeneration did not exist in the absence of severe knee degeneration. The effect of weight on joint degeneration was joint-specific whereby weight had a significantly greater effect on the knee. Ankle grades increasingly did not match within a donor as the grade of degeneration in either the left or the right knee increased.

Conclusions: Gender and body type have a greater effect on knee joint integrity as compared to the ankle, suggesting that knees are more prone to internal causative effects of degeneration. We hypothesize that the greater variability in joint health between joints within an individual as disease progresses from normal to early signs of degeneration may be a result of mismatched limb kinetics, which in turn might lead to joint disease progression.

Figure 1

Representative tali. Examples of joint degeneration grades: (a) grade 0, (b) grade 1, (c) grade 2, (d) grade 3, (e) grade 4.

Figure 2

Distribution of knee/tali donors per decade of life. Mean age = 60 years.

Figure 3

(a) and (b) Distribution of grades per decade for (a) knee and (b) ankle joints. By the third decade, the severity of knee grades increased in comparison to the ankle. By the eighth decade, no knee was normal in appearance, whereas some normal tali were observed into the tenth decade.

Figure 4

Distribution of grades for the left and right knees and ankles separately.

Figure 5

Distribution of grades for male and female knees and ankles separately.

Figure 6

Distribution of knee and ankle grades separated according to relative body type (as assessed visually). Knees from obese donors displayed more severe degeneration (grades 3 and 4) than did joints from lightweight or normal-weight donors.

Figure 7

Survival curves of the ankle (red) and the knee (blue), reflecting the probability of samples attaining grades (a) 1, (b) 2, (c) 3 or (d) 4. There is a significant difference between expected survival of knees and ankles (P = 0.001).

Figure 8

Survival curves of the male (red) and female (blue) samples in (a) the knees reaching the grade 3 and (b) the ankles reaching the grade 2. There were significant differences between the curves of the male and female knees when grade 3 (Figure 8a) or 4 was defined as being degenerate (for each P < 0.05)