Articular Cartilage of the Knee by Unknown

Author:Unknown
Language: eng
Format: epub
ISBN: 9781493975877
Publisher: Springer New York

8.2.2 Physical Activity and Exercise

The term “physical activity ” encompasses all forms of activity that involves expenditure of calories with an increased heart rate. Physical activities include everyday activity (daily walking within and out of the house, housework, gardening, cycling, pleasure- or work-related activity), active recreation (recreational walking, cycling, dancing), sport (informal or structured competitive), and exercise. Physical activity in childhood has been shown to be positively associated with cartilage growth and development in randomly selected healthy children without knee pain or injury [60]. Among young adults (31–41 years old), physical activity has been shown to be associated with an increased tibial cartilage volume and reduced cartilage defects [61]. Among adults (51–81 years old) participating in more frequent occupational physical activities, individuals with high baseline cartilage volume modified their risk for knee OA; however, individuals with low baseline cartilage volume had greater medial cartilage volume loss compared to those who were relatively more inactive [62].

Aging of joint and periarticular tissues may be accelerated by joint injury. With joint pain, maintaining an active life and participating in sports can be challenging. Joint inactivity or microgravity has been associated with tissue atrophy, whereas physical exercise has been shown to increase blood circulation to the joint tissues which helps to reduce inflammation [63–65]. The latter was corroborated in a study that showed running decreased knee intra-articular pro-inflammatory cytokine concentration [66].

High impact exercises (such as running and jumping) and weight-bearing exercises (such as strength training, jogging, tennis, running, and weightlifting) which involves work force against gravity can put “stress” on the bones [67]. For instance, the jolting motions involved in running can cause an impact of 2.5 times the runner’s body weight with each step. In response to this “stress,” the osteoblasts build new dense bone and maintain bone mass [68]. On the other hand, low impact exercises like yoga, biking or swimming place less stress on the bones. Moderate physical activity, including regular walking, was associated with a lower incidence of bone marrow lesions. Research on the effect of exercise on cartilage show its tendency to weaken without regular loading, similar to muscle, bone, ligament, and tendon [69–71]. There are differences in cartilage thickness between individuals, but what remains unclear is whether physical activity or certain exercises are significant contributors to this finding.

In healthy individuals, regular activity facilitates cycles of ECM turnover within cartilage and chondrocytes maintain the cartilage homeostasis. Daily regular activities and mobility are sufficient to maintain adequate knee cartilage lubrication and diffusion of nutrients through the cartilage. Besides strengthening joint tissues (muscle, bone, articular cartilage, ligaments, and tendons), moderate activities also enhance articular cartilage lubrication. The production of synovial fluid that maintains joint lubrication increases with exercise. Excessive synovial fluid produced by the synovial membrane is a short-term or acute response to aggressive exercise [72]. However, too little exercise or immobilization eventually compromises the lubricant properties of cartilage. With long periods of immobility, the joints may become stiff and lose some of their movement range. Knee mobility exercises such as knee bending may encourage a steady supply of normal synovial fluid.

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