Background/Purpose: Knee osteoarthritis (OA) is one of the major causes of disability among elderly. Knee replacement (KR) is the final effective treatment of OA after other treatment attempts fails to provide pain relief. Quadriceps muscle is the major stabilizer of knee joint. Our purpose was to evaluate the relationship between quadriceps muscle quality and total knee replacement incidence in patients having OA.

Methods: Cases were defined as the participants who had a KR between 36 to 60 months visit. Controls were matched by age (within 5 years), sex and baseline central Kellgren-Lawrence grade (0/1, 2, 3 and 4). Participants who had available mid-thigh MR imaging scans (15 contiguous slices, 5mm slice thickness) at baseline and 24 month follow-up were evaluated. Femoral insertion point of oblique tendon of adductor magnus muscle was determined as a landmark for each thigh for matching purposes to account for differences thigh length and body surface area (BSA). This slice was chosen for segmentation and cross-sectional area (CSA) measurements of quadriceps, hamstring muscles and intramuscular, subcutaneous fat (QM, HM, IMF, SCF). Segmentation was done by a radiologist who was blinded to TKR status. A second radiologist segmented 20 legs for reliability measurements. Muscle quality (MQ) was defined as the peak muscle strength divided by muscle CSA. Four pairs were excluded for baseline and four additional pairs were excluded for follow-up MQ measurements because the peak strength values were not available. Conditional logistic regression analysis was used for statistical evaluation. 

Results: There were 46 case-control pairs of thighs and knees (54 right, 38 left) from Osteoarthritis Initiative (OAI) database that were included in this case-control study. The mean ± SD age and BSA were 63.3 ± 8.9, 1.99 ± 0.23 respectively. Fifty percent of the participants were female and 7.6% were African American. Inter and intraobserver ICC was 0.997 and 0.999 respectively. In adjusted models, QMCSA was smaller in case group both in baseline and follow-up images (p=0.17, p=0.24 respectively). Baseline and follow up QM quality (QMQ) was not significantly different between cases and controls. HMCSA, HMQ, SCFCSA and IMFCSA measurements did not show any significant differences between case and controls.

Conclusion: QMCSA seems to be significantly smaller in case group even the QMQ is not significantly different. We think that QMCSA has a potential of being one of the biomarkers for predicting future TKR candidates. Future studies may address the importance of increasing QMCSA by life style modifications and its effects on progression of disease.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/smaller-baseline-and-follow-up-quadriceps-muscle-cross-sectional-area-increases-the-odds-of-knee-replacement-in-knee-osteoarthritis/