Some trials define a dichotomous outcome of clinically significant pain relief as having been achieved above a specific threshold on a pain score, for example, WOMAC pain VAS. However, there is no standard threshold and each such trial should be considered individually.

A retrospective or prospective follow-up study. Groups of individuals to be followed up are defined on the basis of presence or absence of exposure to a suspected risk factor or intervention. A cohort study can be comparative, in which case two or more groups are selected on the basis of differences in their exposure to the agent of interest.

A range of values which provide a measure of certainty in a statistic. The interval is calculated from sample data, and generally straddles the sample estimate. The 95% confidence value means that if the study is repeated many times, then 95% of the estimates of the statistic in question will lie within the confidence interval.

The Cochrane Library consists of a regularly updated collection of evidence-based medicine databases including the Cochrane Database of Systematic Reviews (reviews of randomised controlled trials prepared by the Cochrane Collaboration).

A concept reflecting the extent to which a course of action agreed between clinicians and a patient is actually carried out, often but not solely used in the sense of therapeutic interventions or behavioural changes.

A type of economic evaluation where, for each intervention, various health outcomes are reported in addition to cost, but there is no overall measure of health gain.

An economic study design in which consequences of different interventions are measured using a single outcome, usually in natural units (for example, life-years gained, deaths avoided, heart attacks avoided, cases detected). Alternative interventions are then compared in terms of cost per unit of effectiveness.

A form of cost–effectiveness analysis in which the units of effectiveness are quality adjusted life-years (QALYs).

In this guideline, electrotherapy is used to describe any intervention suggested to be useful in controlling pain in osteoarthritis through applying local electrical or electromagnetic stimulation.

See rescue medication

A pragmatic approach to assess the real-life effectiveness of a programme of healthcare interventions as a complete package, typically around information and communication. Measurements are made before and after the implementation of the new programme. The study design suffers from contemporaneous confounding changes in the healthcare system, lack of blinding, primacy/recency effects and a historical control group.

The cost of one alternative less the cost of another.

The ratio of the difference in costs between two alternatives to the difference in effectiveness between the same two alternatives.

A tool for classifying severity of osteoarthritis based on radiographic findings.

A range of physiotherapy techniques where the affected joint (typically the hip) is manipulated and stretched beyond the range of motion that the person with osteoarthritis is able to use.

A statistical technique for combining (pooling) the results of a number of studies that address the same question and report on the same outcomes to produce a summary result.

Features of the design or reporting of a clinical study which are known to be associated with risk of bias or lack of validity. Where a study is reported in this guideline as having significant methodological limitations, a recommendation has not been directly derived from it.

A retrospective or prospective study in which the investigator observes the natural course of events with or without control groups, for example cohort studies and case-control studies.

A measure of treatment effectiveness: the odds of an event happening in the intervention group, divided by the odds of it happening in the control group. The ‘odds’ is the ratio of non-events to events.

The probability that an observed difference could have occurred by chance. A p-value of less than 0.05 is conventionally considered to be ‘statistically significant’.

Refers to the level of comfort, enjoyment and ability to pursue daily activities.

A measure of health outcome which assigns to each period of time a weight, ranging from 0 to 1, corresponding to the health-related quality of life during that period, where a weight of 1 corresponds to optimal health, and a weight of 0 corresponds to a health state judged equivalent to death; these are then aggregated across time periods.

A trial in which people are randomly assigned to two (or more) groups: one (the experimental group) receiving the treatment that is being tested, and the other (the comparison or control group) receiving an alternative treatment, a placebo (dummy treatment) or no treatment. The two groups are followed up to compare differences in outcomes to see how effective the experimental treatment was. Such trial designs help minimise experimental bias.

In this guideline, this is an outcome recorded by some studies. The rate of rescue medication use is the rate at which participants had to use a stronger medication (typically for analgesia).

A term used for aspects of osteoarthritis care which a person can do for themselves with advice from the primary care team, such as the GP, nurse, physiotherapist, occupational therapist and from information leaflets.

A measure of the extent to which small changes in parameters and variables affect a result calculated from them. In this guideline, sensitivity analysis is used in health economic modelling.

Any national organisation, including patient and carers’ groups, healthcare professionals and commercial companies with an interest in the guideline under development.

A result is deemed statistically significant if the probability of the result occurring by chance is less than 1 in 20 (p<0.05).

Research that summarises the evidence on a clearly formulated question according to a pre-defined protocol using systematic and explicit methods to identify, select and appraise relevant studies, and to extract, collate and report their findings. It may or may not use statistical meta-analysis.

Formal ascertainment and review of the evidence surrounding a health technology, restricted in the current document to appraisals undertaken by NICE.

A method of deriving health utilities from clinical outcomes through finding an equation that best links the two.

A number between 0 and 1 that can be assigned to a particular state of health, assessing the holistic impact on quality of life and allowing states to be ranked in order of (average) patient preference.