Ingham, Sarah Louise
(2010)
Knee pain in the community: risk factors, incidence, and outcome.
PhD thesis, University of Nottingham.
Abstract
Background: Knee pain affects 1 in 4 people over 55 years, and is a leading cause of disability in the elderly (Peat et al, 2001). Whilst the prevalence of knee pain has been examined, the natural history of knee pain and associated risk factors remain unknown (O’Reilly, 1996).
Objectives: to determine in a community sample over a 10 year period: [1] the incidence of knee pain; [2] the outcome of knee pain; and [3] risk factors for both incidence and outcome of knee pain.
Materials and method: This was a retrospective cohort study. Baseline data were collected between 1996-1999, and the cohort was reviewed during 2007-2008. Knee pain was defined as pain around the knee for most days of at least a month. Participants without knee pain at baseline who developed knee pain during the subsequent 10 years were defined as incident cases. Participants with knee pain at baseline who reported worsening of symptoms, improvement of symptoms, no change in symptoms, or who underwent TKR during the past 10 years were defined as outcome cases. Other measures included: age of onset and time from baseline to the first episode of knee pain. Putative risk factors measured at baseline included age, gender and body mass index (BMI); risk factors assessed at follow-up included knee malalignment and foot angulation. Relative risk (RR) was estimated using odds ratio (OR) or hazard ratio (HR) depending on outcomes. Confounding factors were adjusted using logistic regression or COX regression.
Results: 9,429 participants were questioned at baseline (2,868 knee pain positive/6,397 knee pain negative). After 10 years, 5,479 were eligible for follow-up. Of them 3,109 responded and 424 underwent x-rays at both baseline and follow-up. The baseline age of this cohort ranged between 40-83 years, with a mean age of 57 years old; 1,725 (55.5%) were women. The incident rate for knee pain cases during the 10 year follow-up period was 742/2,156 (34.4%); this was similar in men (32%) and women (35%). During the 10 year period 250 (27.4%) of the 914 people with pain at baseline experienced worsening of their symptoms, with 81 (8.9%) requiring total knee joint replacements (TKR). A number of risk factors were explored. Obesity (OR 2.19; 95%CI 1.49, 3.22) and varus malalignment (OR 2.82; 95%CI 1.57, 5.06) significantly associated with incident knee pain, whereas back pain (aOR 1.47; 95%CI 1.02, 2.10) and physical work (aOR 1.88; 95%CI 1.02, 3.50) were related to poor outcome.
Conclusions: For people over the age of 40 years old, 1 in 3 will develop significant knee pain in the next 10 years. Of people with knee pain, 1 in 4 will worsen over a 10 year period and 1 in 11 will require surgery. A number of risk factors were identified including both systemic/constitutional and more local biomechanical factors. This could have practical implications for primary and secondary prevention particularly in relation to modifiable risk factors, such as reduction in BMI, occupational protection of the knees and possible adjustment of knee malalignment.
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