A new study indicates that adolescent anterior knee pain may be a predisposing factor to patellofemoral osteoarthritis many years later.
Physicians have traditionally told patients that adolescent anterior knee pain is usually self-limiting and benign. But the stud and by Dr. Matthew R. Utting his colleagues from Southmead Hospital in Westbury-on-Trym, England, showed that 22% of patients with patellofemoral arthritis who had undergone arthroplasty recalled having anterior knee pain as an adolescent.
In contrast, only 6% of patients who had undergone medial unicompartmental arthroplasty recalled adolescent anterior knee pain, a significant difference (Knee 2005;12:362–5).
The investigators sent questionnaires to 150 patients who had undergone patellofemoral arthroplasty and to another 150 patients who had undergone medial unicompartmental arthroplasty. The response rate was an impressive 77% from the medial unicompartmental arthroplasty group and 79% from the patellofemoral arthroplasty group.
The mean patient age was 67 years in the patellofemoral group and 68 years in the medial unicompartmental arthroplasty group, a difference that was not statistically significant.
Patients in the patellofemoral group experienced a mean of 16 years of pain before the arthroplasty, compared with 9 years for the medial unicompartmental arthroplasty group. Among the patellofemoral group, 16% recalled previous trauma of the patella, compared with 6% of the medial unicompartmental arthroplasty group.
There was no difference in the number of patellar fractures, with two individuals in each group reporting this. Many of the individuals with patellofemoral osteoarthritis reported having symptoms for at least 20 years prior to their arthroplasty, suggesting that the problem had been more or less continuous throughout their lives and that it may have arisen directly from anterior adolescent knee pain.
The investigators noted several limitations of their study. It was retrospective and relied on patients' memories from 40–50 years prior. Furthermore, it's impossible from this study to determine how many people with adolescent anterior knee pain go on to develop patellofemoral osteoarthritis.