OVERUSE INJURIES

Konradsen (17) examined hips and knees of long distance runners who had been competing for at least 40 years to a matched con- trol group. Interestingly, there was no difference between the two groups. Sohn (18) followed former varsity runners for a mean of 25 years. Comparing them to former swimmers, he could not find any association between heavy mileage or years of running to the development of OA. Panush (19) assessed knees, hips, ankles and feet of marathon runners (weekly mileage averaged 45 km for 12 years) and compared them to non-runners. He did not find any notable differences. Lane (20) investigated the association between running, radiographic hip and knee osteoarthritis and bone mineral density and could not demonstrate a difference between runners and non-runners. Overall, runners did have high- er BMD values. What can we derive from these results? Does it mean that recreational sports are fine but anything beyond that is potentially harmful? It is important to note that all the above studies did not consider other factors such as previous injury, pre- mature return to competition and influence of malalignment all of which are potential contributing factors. As for recreational ath- letes, how do we know that runners who continue running for many years are not just genetically predisposed to staying healthy? In response: we don’t!

RISK FACTORS FOR OA WITH RUNNING Obesity, level of physical activity and smoking have been identi- fied as risk factors affecting the incidence of osteoarthritis by the Framingham study (21). While it is not surprising that weight has a direct effect on impact forces (calculated odds ratio 1.6), one can not explain why smokers should have a decreased risk (odd ratio 0.4). Possibly, they are just less physically active and live a less active lifestyle. The changes seen with obesity reverse once an attempt to lose weight has been successful (odds ratio 1.4). Activity has a 3.3 higher risk of degenerative joint disease. One has to mention that this study is a byproduct from the Framingham Coronary Heart Disease Study and included middle- aged to elderly subjects only. These results are therefore subject to selection bias. Let’s peruse the literature to see what other fac- tors may contribute to joint degeneration.

Previous injury Previous injury has clearly been identified as a risk factor for the development of osteoarthritis. Gelber (22) demonstrated that knee injuries in young adults doubles the risk of osteoarthritis later in life. Deacon (16) has also shown that intra-articular injuries to the knee during Australian Rules Football such as meniscal injuries contribute significantly to the prevalence of osteoarthritis. Davis (23) showed that knee injury was a stronger predictor of unilateral OA than was obesity demonstrating the effect of injury. Wolcott (24) demonstrated that patients with meniscal injuries, previous meniscectomies, articular cartilage injuries, unstable knees and underlying malalignment, develop osteoarthritis. Roos (25) summarised current evidence in a review article. Knee injuries are a strong predictor of OA. In addition, deconditioning (muscle weakness, proprioceptive deficits) of the musculoskeletal system caused by the injury itself or subsequent surgery (ie. meniscectomies, reconstruction of the anterior cruciate ligament) result in increased joint loads. Therefore there is clear evidence that injuries can contribute to secondary joint changes leading to osteoarthritis particularly if recovery is incomplete.

12 THOUGHT PROVOKERS

1) Are people that are able to continue marathon running not just a selection of the genetically advantaged?

2) As cartilage only has a slow metabolic rate, is MRI sensitive enough to pick up those changes at all?

3) What about supplements like glucosamine? Can they help recovery?

Trade your opinions by logging in to www.sportex.net and visit- ing Issue 30 sportEX medicine on our new discussion forum.

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Malalignment There is only one study investigating the effect of malaligment on the development of osteoarthritis. Sharma (26) has shown that malaligment is a major risk factor for the development of osteoarthritis. In addition, they demonstrated a decline in func- tion as little as 18 months after detection. Indirect evidence has been demonstrated by studies assessing the biomechanical effects of high tibial realignment osteotomies. Heller examined the effect of high tibial osteotomy on joint loading. He showed that varus deformities of 10 degrees resulted in an increase in peak contact force from 3.3 times BW to 7.4 BW. Wolcott (24) reviewed the cur- rent literature. He reports that there is clear evidence that osteotomies around the knee unload isolated medial or lateral compartments leading to decrease in symptoms. We can conclude that there is biomechanical evidence from cadaver studies that osteotomies unload joints. As a logical consequence, malalign- ment has to lead to increased joint loads.

Obesity There is general agreement that obesity is associated with osteoarthritis. Manninen (27) demonstrated a linear relationship with a relative risk of 1.4. Other authors (21, 23, 28,29) have also confirmed this fact. Sturmer (30) believes that this higher inci- dence is due to mechanical factors rather than systemic effects. From a practical perspective, there is no doubt that if you are sig- nificantly overweight, do not run.

IN CONCLUSION It therefore seems that clinical studies are unable to answer the question as to whether running can cause or contribute to the development of osteoarthritis. Some authors who followed up a randomly selected group of former elite athletes have demon- strated a higher risk of osteoarthritis in their population. However, it could be argued that these studies do not present clear evidence and are fraught with selection bias. This statement unfortunately also applies to studies that followed-up a random selection of distance runners. Recreational athletes who were unable to continue with running for whatever reason were auto- matically excluded.

Nevertheless, there is clear evidence that previous injuries to a joint of the lower extremity, obesity, malalignment or a combina- tion of the above, are risk factors for OA. Given the fact that run- ning increases impact loading, it would be logical to conclude that weight-bearing activities will speed up the process. The clas- sic case scenario is a 40 year old male former football player with

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