The epidemiology of patellofemoral disorders in adulthood: a review of routine general practice morbidity recording.

AIM: To describe the annual consultation prevalence of different patellofemoral disorders across the adult life span.
BACKGROUND: The knee is the second most common site for musculoskeletal pain. Evidence from sports injury and orthopaedic settings suggests that patellofemoral disorders constitute a significant proportion of knee pain cases, but we have no evidence from general practice - the setting where most patellofemoral problems will present and be dealt with - of the prevalence of consultations for these problems in the different age groups.
METHODS: Age- and gender-stratified annual person consulting prevalence rates (APCPRs) for patellofemoral disorders were calculated using 2006 data from the 'Consultations in Primary Care Archive' (CiPCA) - a fully audited database of continuous morbidity recording used by the general practitioners (GPs) in eight general practices in North Staffordshire.
FINDINGS: A total of 57 555 >15-year-olds were registered with the eight general practices in 2006; 1782 made a knee-related consultation, of which 303 (one-in-six) were coded as patellofemoral disorders (APCPR, 53 per 10 000 persons), suggesting that GPs consider a significant proportion of adult knee pain consulters to have patellofemoral disorders. Twelve patellofemoral disorders diagnosed by the GPs were identified. The non-specific diagnosis of 'anterior knee pain' (AKP) was by far the most common (APCPR, 37.2/10 000). Other more specific diagnoses were rare by contrast, suggesting that specific patellofemoral disorders are rarely diagnosed in general practice (consultation prevalences, in order of most prevalent first: bursitis (7.8/10 000), patellofemoral osteoarthritis (2.3/10 000); APCPRs for the remaining nine diagnoses ranged between 0 and 1.6/10 000). However, the use of alternative less anatomically specific diagnostic codes, such as for 'knee pain', may mean that our estimate of one-in-six is an underestimate of GPs' true attribution rates to patellofemoral joint disorders of people consulting them with knee pain. AKP was seen equally commonly by GPs across all age strata, contradicting the received wisdom that AKP problems are most common among younger adults.