Table 1 Pain terminology as defined by the International Association for the Study of Pain ( http://www.iasp-pain.org )

Nociceptor

A sensory receptor that is capable of transducing and encoding a noxious stimulus

Nociceptors are located in a variety of tissue types including most structures of the articular joint

Nociceptive neuron

A central or peripheral neuron that is capable of encoding noxious stimulation

Sensitization

Increased responsiveness of neurons to normal input or activation of a response by inputs that are normally subthreshold

Can occur in the periphery (nociceptors) or in the CNS pathway

Primary hyperalgesia

Increased response to a stimulus that is normally painful

Occurs at the site of insult; results from peripheral nociceptor sensitization

Secondary hyperalgesia

Increased response to a stimulus that is normally painful

Occurs outside the site of insult in tissue that is not injured; results from central neuron sensitization

Allodynia

Pain due to a stimulus that does not normally evoke pain

Results from central neuron sensitization

Temporal Summation

Increased pain to application of the same stimulus repetitively over a brief period of time

Enhanced in patients with osteoarthritis; surrogate measure of central neuron excitability

Conditioned pain modulation

Application of a noxious stimulus distant to the test area (such as leg) produces analgesia (such as arm)

Decreased in patients with osteoarthritis; surrogate measure of central inhibition; also referred to as diffuse noxious inhibitory control (DNIC)

Pain catastrophizing

Tendency to magnify the consequences of the pain and to feel helpless in managing the pain

Higher levels associated with higher OA pain, and worse outcomes (disability, pain)

Self-efficacy

Lower levels are associated with worse outcomes (function, pain)

Fear of pain/movement

Excessive expectation that physical activity will worsen pain and function

Higher levels are associated with worse outcomes (function, disability, pain)