Structural Correlates of Pain in Osteoarthritis

Editorial Review

Structural Correlates of Pain in Osteoarthritis

T. Neogi

Clinical and Experimental Rheumatology 2017;35 (Suppl. 107):S75-S78

JACO Editorial Reviewer: Daniel P. Dock, DC, FACO

Published: December 2017
Journal of the Academy of Chiropractic Orthopedists
December 2017, Volume 14, Issue 4

The original article copyright belongs to the original publisher. This review is available from: http://www.dcorthoacademy.com

© 2017 Dock and the Academy of Chiropractic Orthopedists. This is an Open Access article which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

AUTHOR’S ABSTRACT:

Osteoarthritis (OA) is the most common form of arthritis, with knee OA itself being among the most common conditions and a leading cause of disability among older adults worldwide. Pain is a key symptom in the decision to seek medical attention, yet available therapies for managing OA are limited with only minimal or moderate efficacy. Current approaches to pain management in OA have been rather non-specific, limited to acetaminophen or NSAIDs primarily, without targeting underlying structural lesions that may be contributing to pain in OA. With the advent of MRI, a number of studies have noted the importance of bone marrow lesions and synovitis/effusion to the pain experience in OA. These pathologic features are therefore attractive treatment targets, with some proof-of-concept studies demonstrating the potential efficacy of targeting these lesions. Another increasingly recognised important contribution to pain in OA is sensitisation, which is associated with pain severity. Synovitis/effusion have been identified as potentially leading to development and worsening of sensitisation. Much work remains to be done in understanding the mechanisms by which structural pathology causes pain; such insights are urgently needed to develop new treatment approaches to help millions of people worldwide who are burdened by pain from OA.

Editorial Review:

Knee Osteoarthritis (OA) is among the most common conditions and leading cause of disability among older adults. With the advent of MRI, a number of studies have noted the importance of bone marrow lesions and synovitis effusion to the pain experience in OA. Another increasing recognized important contribution to pain in OA is sensitisation. [Editor’s note: The original article author’s spelling of sensitisation, rather than sensitization, is maintained in this Editorial Review]

Results: Approximately 10-12% of the adult population have symptomatic OA of any joint. Knee OA is a leading cause of disability among older adults, accounting for a greater risk of mobility disability.

One barrier to understanding the genesis of pain in OA is the so-called “structure-symptom discordance”, some individuals have radiographic changes with minimal symptoms, while others have more significant pain with only minimal (if any) structural pathology noted on radiograph. Findings of osteophyte with joint space narrowing characterized as radiographic OA, while its combination of symptoms (i.e. pain, aching, stiffness) in the same joint attributable to OA is considered to be symptomatic OA. The discordance diminishes with more severe stages of disease. It has been recognized that radiographs are relatively insensitive to numerous pathologic changes, and are better visualized on MRI.

Something within the knee must be contributing to symptoms. Joint replacement, intra-articular lidocaine injection, and intra-articular corticosteroid injection give relief of pain.

As OA progresses, neurovascular invasion may disrupt the osteochondral junction, accompanied by growth of sensory nerves and increased expression of nerve growth factor (NGF), which can facilitate sensitisation. Neurobiologic mechanisms have been recognized, particularly of sensitisation.

MRI studies give further insight into structural pathology contributing to OA pain. MRI studies have shown subchondral bone changes (bone marrow lesions), and synovitis/effusion. The bone marrow lesions and synovitis/effusion have been associated with pain and with pain fluctuation.

Use of a patellofemoral knee brace caused reduction in pain and reduction of bone marrow lesions.

Meniscal lesions are common in OA. Meniscal tears were equally occurring among those with knee pain as those without knee pain. MRI findings in knees of older adults can be challenging as 89% of people without any radiographic evidence of knee OA have at least one MRI feature, seen in both painful and pain-free knees.

The contribution of structural joint pathology to the pain experience in OA remains incompletely understood.

MRI sheds light onto specific pathologic features that may play an important role in causing pain.

Factors beyond structural pathology also contribute to the pain experience factors, including psychologic factors.

Pain sensitisation and the overall efficiency of CNS pain modulation mechanisms, merit further studies.

JACO Editorial Summary: Two points that jumped out at me when reading this article was the reduction in pain and the reduction of bone marrow lesions when the patient used a patellofemoral knee brace, and the strengthening of the lower extremity muscles helping with proper patellar glide. This outlines the possibility of using arch supports to cause relief of pain and relief of mobility disability (remember, the “foot goes flat, and the leg twists in” causing twisting of the knee structures).

  • Knee OA was pointed as a leading cause of disability in older adults, accounting for a greater risk of mobility disability. This is important considering deep venous thrombosis, pneumonia, cardiovascular conditions, and cerebrovascular conditions.
  • Patients with knee pain may have normal appearing radiographs; osteoarthrosis may be revealed on the radiographs of patients without knee pain. The article points out that there can be knee pain with normal appearing x-rays.
  • Sensitisation can explain why the patient can have more pain than is justified by the exam.
  • The future: Stem Cell Injections and Platelet-Rich Plasma (PRP) are now having success in some cases for pain relief and even reduction of MRI visible bone marrow edema. This is important as it may help take away some of the mobility disability (and the adverse conditions that may occur with mobility disability).