You have to sift the evidence carefully to make sense of whether being active puts you at greater risk of joint disease in later life. Sam Oussedik, Laurence James and Fares Haddad report

Athletes are in no way immune to arthritis; it is a common and perplexing problem among this group. Indeed, despite there being an obvious public health interest in understanding the potential risk of exercise-induced osteoarthrosis (OA) in weight-bearing joints, very little is known about it. This may in part be because of the large number of factors that can contribute to OA, making it difficult to pin down the effect of isolated influences such as exercise or participation in sport.

What is osteoarthritis?

‘Osteoarthritis’ covers a widely varying group of conditions characterised by abnormality in the articular cartilage on the ends of bones and surfaces of joints. The disease can be primary, in the absence of any predisposing factors, or secondary, resulting from a known condition, in one of four categories:

• metabolic disorders;
• anatomical derangement;
• major trauma or surgery to a joint;
• inflammatory disease.

Osteoarthritis, most commonly of the hip and knee, is a significant and disabling condition for many current and former athletes. The resulting pain and loss of movement can limit function. Although former athletes report symptoms at similar rates to the population in general, they tend to have higher pain thresholds, which may lead to a relative underestimation of their problems.

We have a poor understanding of the mechanisms by which sports participants may develop OA. Several models have been proposed. We know, for instance, that sporting activity increases the chances of suffering minor trauma to the articular cartilage. This will alter the way in which forces are transmitted through the joint, risking further damage, and may also alter the force transfer through adjacent joints, putting these in jeopardy.

Sporting activity also increases the chances of damage to intra-articular (internal joint) structures. Taking the knee as an example, a meniscal (shock-absorbing cartilage) tear can result in chondral (articular cartilage) damage. Rupture of a knee ligament, such as the anterior cruciate ligament (ACL), is also associated with a greater risk of articular damage, although some argue this may be reversed by early ACL reconstruction.

In a study of Swedish men aged 50 to 80(1), the incidence of OA of the hip was, at 8%, four times greater among former athletes than among controls of a similar age (2%). Similar but less convincing results were recorded for the knee. Neck and shoulder disorders – which are common problems among recreational sportspeople such as overhead athletes and weightlifters – were less prevalent among former athletes. For all other joints and musculoskeletal disorders the distribution was similar between the groups.

A second study, of hospital admissions in Finland for hip, knee and ankle OA, found a greater incidence overall in former international athletes than among controls who had been healthy at the age of 20. This study also identified differences within the athlete groups, with the mean age of first hospital admission being lowest among people who’d played mixed sports (58.2 yrs), and highest in endurance athletes (70.6 yrs). The mean age in the control group was 61.2 years, very close to that for power sports (61.9 years). This result suggests that the higher than normal rates of OA, at least in endurance athletes, may be attributable to advanced age-related changes rather than the sport itself(2).

Other studies to determine the relationship between previous lower-limb loading and current self-reported hip and knee disability in elite international athletes have found that these athletes report less hip disability than ‘normal at age 20 control’ subjects. But among team-sport athletes (in particular ball-game activities) there was a higher risk of knee disability. The relationship between vigorous athletic activity and knee function is controversial, because such sports often involve a high risk of knee injury, which is likely to lead to pain, disability and osteoarthritis(3).

We also now know (Gross et al)(4) that the risk of OA among former elite athletes is similar to that of members of the general population who say they have pursued long-term sporting activity, which suggests that duration may be more significant as a contributory factor than intensity or frequency of training. And although these active groups are exposed to increased risk of hip and knee OA, Gross et al have found that regular moderate jogging in middle age is likely to help maintain physical function.
For the majority of less active exercisers, recreational physical activity seems neither to increase nor to decrease the risk of OA to any marked extent.

Compared with controls of similar age, X-rays of most large joints of former athletes have shown up more frequent signs of OA. This association increases further after adjusting for height and weight differences. Osteophytes (bony growths) are most commonly found in affected knee and hip joints (especially in tennis players) and patello-femoral joint (knee cap, especially in runners). With the exception of the knee, joint-space narrowing was also a common feature in the joints affected(5).

How to manage OA

• Non-operative
  The focus of any treatment is to allow for pain-free participation in sports and activities, so that the patient can continue to enjoy the benefits of regular exercise, and perhaps delay the need for surgery. Rehabilitation plays a key role in all non-operative treatment for arthritis, particularly to restore motion.
  A progressive, phased regime is very important. Initially drugs are used, such as non-steroidal anti-inflammatories, with or without the use of ‘cartilage protective’ agents, such as glucosamine, to maintain mobility and pain control. Corticosteroid or visco-supplementation joint injections are usually given at this stage.
  Physiotherapists may then use sport-specific open, and later closed-kinetic-chain non-weight-bearing exercises for the joints involved. These proprioceptive, muscle stretching and strengthening aspects of physiotherapy can have a beneficial effect within three months.
• Operative
  Early arthritis in athletes can be treated with minimally invasive surgery, for instance to
  remove loose debris, clean up inflamed and torn tissues, undertake capsular release, and other associated procedures such as rotator cuff repair and decompression. Arthroscopic (keyhole) techniques in many cases enable surgeons to diagnose and symptomatically treat joint stiffness and pain, prolonging active careers. Post-operative physiotherapy is very important in all cases.

To help prevent the early onset of degenerative change and restore function, surgery focuses on reconstructing damaged soft tissue. ACL reconstruction, for instance, has become established as an important procedure to restore normal knee biomechanics. Not only does it treat symptomatic instability in the knee, allowing
a return to high level sport, it also improves the chances of avoiding further damage to internal joint structures such as the menisci (shock absorbers) and associated degenerative changes(6).

Where there is advanced degenerative change associated with an underlying anatomical defect, such as genu varum (bow legs), bone surgery may be indicated. This has the advantage of stabilising damage to articular cartilage and re-establishing normal joint alignment, while conserving bone stock. In the younger patient it allows more function than they could expect from joint replacement surgery.

Joint replacement surgery remains the best treatment for symptomatic OA of the hip and knee. But active people who have joint replacement should not expect necessarily to return to the same level of sporting activity post-operatively.

Two studies have examined the post-operative prospects for recreational sportspeople after joint surgery. With total hip replacement, patients may expect to return to low-impact sports, such as walking, bowls or aqua aerobics, but they are less likely to be able to carry on with tennis, jogging or golf(7). The picture is similar for total knee replacement(8).

Newer procedures, such as unicompartmental knee replacement and hip resurfacing may improve the chances of a successful return to a broader range of sporting activities. This has certainly been our experience, with many who are still competing. However, as yet there is little objective medium-term data to confirm this.

Research prospects

Current research is focused on providing a more biological approach to the treatment of OA. Tissue engineering involving the use of stem cells is one avenue: if one views OA as an imbalance between local tissue destruction and repair, then applying progenitor cells locally allows for a restoration of the pool of cells from which new cartilage can form. This approach has had some success in animals, and human applications are not too far away.

Advances in implant design may also hold out the promise of better performance after total joint surgery. Newer technologies, such as autologous cultured chondrocyte implantation, tissue-engineered cartilage, growth factors and acellular matrices, may significantly alter our ability to manage osteoarthritis with greater success.

References
1. Vingard E, Sandmark H, Alfredsson L ‘Musculoskeletal disorders in former athletes. A cohort study in 114 track and field champions’ Acta Orthop Scand 1995 Jun; 66(3):289-91
2. Kujala UM, Kaprio J, Sarna S ‘Osteoarthritis of weight bearing joints of lower limbs in former elite male athletes’ BMJ 1994 Jan; 308(6923):231-4
3. Kettunen JA, Kujala UM, Kaprio J, Koskenvuo M, Sarna S ‘Lower-limb function among former elite male athletes’ Am J Sports Med 2001 Jan-Feb; 29(1):2-8
4. Gross P, Marti B ‘Sports activity and risk of arthrosis’ Schweiz Med Wochenschr 1997 Jun; 127(23):967-77
5.Spector TD, Harris PA, Hart DJ, Cicuttini FM, Nandra D, Etherington J, Wolman RL, Doyle DV ‘Risk of osteoarthritis associated with long-term weight-bearing sports: a radiologic survey of the hips and knees in female ex-athletes and population controls’ Arthritis Rheum 1996 Jun; 39(6):988-95
6. Daniel DM, Fithian DC ‘Indications for ACL surgery’ Arthroscopy 1994; 10(4):434-441
7, Chatterji U, Ashworth MJ, Lewis PL, Dobson PJ ‘Effect of total knee arthroplasty on recreational and sporting activity’ ANZ J Surg 2005 Jun; 75(6):405-8
8. Bradbury N, Borton D, Spoo G, Cross MJ ‘Participation in sports after total knee replacement’ Am J Sports Med 1998 Jul-Aug; 26(4):530-5