Does Running Cause Osteoarthritis?

The role of impact forces and foot pronation: a new paradigm

OBJECTIVE

This article discusses the possible association between impact forces and foot pronation and the development of running-related injuries, and proposes a new paradigm for impact forces and foot pronation.

DATA SOURCES

The article is based on a critical analysis of the literature on heel-toe running addressing kinematics, kinetics, resultant joint movements and forces, muscle activity, subject and material characteristics, epidemiology, and biologic reactions. However, this paper is not a review of the literature but rather an attempt to replace the established concepts of impact forces and movement control with a new paradigm that would allow explaining some of the current contradictions in this topic of research.

STUDY SELECTION

The analysis included all papers published on this topic over the last 25 years. For the last few years, it concentrated on papers expressing critical concerns on the established concepts of impact and movement control.

DATA EXTRACTION

An attempt was made to find indications in the various publications to support or reject the current concept of impact forces and movement control. Furthermore, the results of the available studies were searched for indications expanding the current understanding of impact forces and movement control in running.

DATA SYNTHESIS

Data were synthesized revealing contradictions in the experimental results and the established concepts. Based on the contradictions in the existing research publications, a new paradigm was proposed.

CONCLUSION

Theoretical, experimental, and epidemiological evidence on impact forces showed that one cannot conclude that impact forces are important factors in the development of chronic and/or acute running-related injuries. A new paradigm for impact forces during running proposes that impact forces are input signals that produce muscle tuning shortly before the next contact with the ground to minimize soft tissue vibration and/or reduce joint and tendon loading. Muscle tuning might affect fatigue, comfort, work, and performance. Experimental evidence suggests that the concept of "aligning the skeleton" with shoes, inserts, and orthotics should be reconsidered. They produce only small, not systematic. and subject-specific changes of foot and leg movement. A new paradigm for movement control for the lower extremities proposes that forces acting on the foot during the stance phase act as an input signal producing a muscle reaction. The cost function used in this adaptation process is to maintain a preferred joint movement path for a given movement task. If an intervention counteracts the preferred movement path, muscle activity must be increased. An optimal shoe, insert, or orthotic reduces muscle activity. Thus, shoes, inserts, and orthotics affect general muscle activity and, therefore, fatigue, comfort, work, and performance. The two proposed paradigms suggest that the locomotor system use a similar strategy for "impact" and "movement control." In both cases the locomotor system keeps the general kinematic and kinetic situations similar for a given task. The proposed muscle tuning reaction to impact loading affects the muscle activation before ground contact. The proposed muscle adaptation to provide a constant joint movement pattern affects the muscle activation during ground contact. However, further experimental and theoretical studies are needed to support or reject the proposed paradigms.

Impact Forces during Heel-Toe Running

Impact forces have been speculated to be associated with the development of musculoskeletal injuries. However, several findings indicate that the concepts of “impact forces” and the paradigms of their “cushioning” may not be well understood in relation to the etiology of running injuries and that complex mechanisms may be responsible for injury development during running. The purposes of this paper are (a) to review impact mechanics during locomotion, (b) to review injuries and changes of biological tissue due to impact loading, and (c) to synthesize the mechanical and biological findings. In addition, directions for future research are discussed. Future research should address the development of noninvasive techniques to assess changes in the morphology and biochemistry of bone, cartilage, tendon, and ligaments; researchers should also try to simulate impact loading during activities such as running, focusing on the interaction of the various loading parameters that determine the acceptable windows of loading for biological tissues.

Degenerative joint disease in hunter-gatherers and agriculturalists from the Southeastern United States

This study examines degenerative joint disease of the major appendicular joints in hunter-gatherers and agriculturalists from northwestern Alabama. Arthritis is highest at the shoulder, elbow, and knee and lower at the hip and ankle. There are virtually no sex differences in the hunter-gatherer group, but in the agriculturalists, males have more severe osteoarthritis than females. The hunters-gatherers have a somewhat greater prevalence of arthritis than the agriculturalists, but the differences are rarely significant. The similarity in osteoarthritis levels over time conflicts with biomechanical evidence, which indicates an increase in usual activities in the agricultural period. Several possible reasons for this are explored, including the suggestion that arthritis is a response to intensive or infrequent activities. Whatever the cause, it is clear that biomechanical data and osteoarthritis are responding to different factors and do not equally represent the level of usual activities.