Abstract
PurposeAlthough disease progression of osteoarthritis has been well documented, pain pathophysiology is largely unknown. This study was designed with two purposes: 1) to characterize patients with knee pain predominantly originating from intra-articular structures and 2) to describe the location and pattern of their pain.Materials and methods103 patients with medial knee osteoarthritis underwent an intra-articular injection of local anesthetics (joint block). At least 70% pain relief was defined as positive for the joint block, while less than 50% as negative. Pain characteristics in patients positive for joint block were evaluated in detail using a knee pain map.ResultsSixty three knees (61%) were positive and 33 knees (32%) were negative. Patients negative for the joint block were significantly higher age, suffered for longer time, and complained more diffuse pain. Although pain at anterior medial area during walk was the most common finding, pain characteristics differed among different knee areas.ConclusionThe characteristics of joint pain are widely variable even in patients with similar radiological features. Extra-articular sources are not negligible especially in older patients with a long history of diffuse pain. Differences in pain characteristics among knee areas should be taken into account when examining the pain source.
Highlights
Knee osteoarthritis (OA) is a major public health problem across the world
Pain at anterior medial area during walk was the most common finding, pain characteristics differed among different knee areas
Differences in pain characteristics among knee areas should be taken into account when examining the pain source
Summary
Knee osteoarthritis (OA) is a major public health problem across the world. Population based studies revealed that symptomatic knee OA is present in 20-30% of the elderly population aged >65 years (Mannoni et al 2003; Andrianakos et al 2006) and its prevalence is increasing due in part to the aging of the population (Leveille 2004). Clinical symptoms are dominated by chronic knee joint pain, which leads to disability, psychological distress, and impaired quality of life. All innervated tissues inside and around the knee joint are potential pain generators in knee OA. Pain generators may differ widely even among patients with similar radiological features, which can contribute to variability in treatment response. It was hypothesized that there would be considerable variation of pain characteristics among patients with similar radiological features. We examined the main pain sources of medial compartment OA, which is the most common form of knee OA, utilizing a diagnostic joint block, in particular reference to intra-articular tissues. Our study was designed with two purposes: 1) to characterize patients with knee pain predominantly originating from intra-articular structures and 2) to describe the location and pattern of their pain
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