Abstract
Where risk factors have been identified in knee and hip osteoarthritis (OA), with few exceptions, no prevention strategies have proven beneficial. The major risk factors for knee OA are advanced age, injury and obesity. However, there is limited or no evidence that they are modifiable or to what degree modifying them is effective in preventing development of knee OA or in preventing symptoms and progressive disease in persons with early OA. The notable exception is the growing epidemic of (sports) injury related knee OA. This review details the biological and clinical data indicating the efficacy of interventions targeting neuromuscular and biomechanical factors that make this subset of OA an attractive public health target, and highlights research opportunities for the future.
Introduction
Osteoarthritis (OA) is the most important rheumatic disease affecting mankind. Where risk factors have been identified, such as in knee and hip OA, with few exceptions, no prevention strategies are well substantiated enough or have proven benefit to justify widespread dissemination. The major risk factors for knee OA are advanced age, injury and obesity1 . However, there is limited or no evidence that they are modifiable or to what degree modifying them is effective or what this would cost in primary prevention (avoiding development of knee OA) or secondary prevention (detecting knee OA early to treat to prevent symptoms and progressive disease).
The notable exception is the growing epidemic of (sports) injury related knee OA. The purpose of this review is to detail the biological and clinical data that make this subset of OA an attractive public health target.
Joint injury increases the risk of knee osteoarthritis
The incidence and prevalence of severe knee injuries requiring medical attention are not well documented. The differential diagnosis of knee injuries includes contusion, subchondral or chondral injury with and without meniscal tear and with and without ligamentous injury or complete tear. In the best studied sports injuries, even injury not precipitating a medical visit appears to be a risk factor for knee OA; the rate is high and increasing worldwide.
Meniscus injuries are common in athletes and the general population2,3. Lohmander and colleagues2 estimate that the cumulative population risk of an anterior cruciate ligament (ACL) injury between 10 and 64 years of age is about 5% based on MRI findings of the acutely injured knee, and for meniscus injury leading to surgery is at least 15%. The incidence of ACL tears is unknown but the MRI-confirmed incidence has been reported at 81 per 100,000 in a hospital-based study4, while a population-based study estimated rates 50 to 100% higher5. The true incidences of both meniscal and ligamentous injuries are likely to be higher since injuries are sometimes unreported, undiagnosed, or diagnosed without MRI.
Over the past two decades there has been an alarming increase in the rate of ACL injuries in young females in sports that involve cutting, jumping and pivoting. Adolescent and mature females in these sports have ACL injuries at a two- to eight-fold greater rate than males participating in the same sports6-8. This, along with a ten-fold increase in the number of women participating in sports since the inception of Title IX, has resulted in a dramatic increase in ACL injuries in females in the US9.
The risk of knee OA from knee joint injury is high; approximately 50% of individuals with an ACL or meniscus tear develop knee OA10-15. A long-term prospective study indicated a relative risk for knee OA of approximately 5 for any previous injury of the knee13.
Thelin and colleagues16 found that knee joint injuries (and not the type of sport or other factors) ac