Background/Purpose:

The objective of the study was to determine whether clinically assessed baseline quadriceps weakness predicts cartilage loss on MRI after 3 years.

Methods:

Subjects 40-79 years old with knee pain were recruited as a random population sample. Stratified sampling technique was used to achieve equal representation of age and gender. A physician examiner assessed quadriceps strength with the subject in the sitting position, using a standardized procedure, previously shown to be reliable. Quadriceps strength was graded from 0 to 2 (0: poor resistance, 1: moderate resistance, 2: full resistance). Subjects were then classified as having either normal strength (grade 2) or quadriceps weakness (grades 0 and 1). Radiographs were graded using Kellgren-Lawrence (KL) 0-4 scale with KL ≥2 considered radiographic osteoarthritis (ROA). MRI of the knees was obtained on a 1.5T magnet at baseline and at 3-year follow up. MRI cartilage was graded on a scale from 0 to 4 and bone marrow lesions (BML) were graded from 0 to 3 by an experienced musculoskeletal radiologist, blinded to time sequence and clinical information. Progression of OA was defined as worsening of cartilage damage by ≥1 MRI grade in at least 2 joint surfaces or ≥2 MRI grades in 1 joint surface. Logistic regression analysis was performed to evaluate the association of quadriceps weakness with whole knee cartilage loss (primary outcome) and with compartment-specific cartilage loss in the medial and lateral tibiofemoral (TF) and patellofemoral (PF) compartments (secondary outcomes). Crude OR, adjusted OR and 95% confidence intervals (CI) were calculated. Adjustments were included for age, sex, BMI, malalignment (varus or valgus), baseline MRI cartilage score (using the maximum cartilage score for the entire joint), baseline presence of BML and follow-up time. 

Of 255 subjects, 163 were seen at a mean follow-up of 3.3 years. Of these, 24.1% had no OA (normal MRI and radiograph), 36.5% had pre-ROA (normal radiograph, abnormal MRI) and 39.4% had ROA (abnormal MRI and radiograph) at baseline. Mean (SD) age was 57.7 (10.1) years, BMI 26.1 (4.2), WOMAC pain score 19.6 (16.8) and 54% were female. Baseline quadriceps weakness was seen in 17.5% of females and 5.3% of males. Quadriceps weakness was a significant predictor of whole knee cartilage loss (OR 3.38, 95% CI 1.01-11.30). In sex-specific analyses, cartilage loss was significantly increased in females with quadriceps weakness (OR 4.91, 95% CI 1.11-21.79), not in males (OR 0.63, 95% CI 0.04-10.09). In compartment-specific analyses, quadriceps weakness was significantly associated with cartilage loss in the medial TF compartment (OR 7.12, 95% CI 1.39, 36.45), while no significant associations were seen in the lateral TF (OR 1.40, 95% CI 0.16-12.02) and PF compartments (OR 2.28, 95% CI 0.35-14.90).

Conclusion:

In this population-based cohort with knee pain, quadriceps weakness at baseline assessed by clinical examination, predicted whole knee cartilage loss in females, not males and predicted cartilage loss in the medial TF compartment after 3 years. A simple clinical test can assist clinicians to predict the risk of progression of early and advanced knee OA.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/quadriceps-muscle-weakness-and-the-risk-of-knee-cartilage-loss-on-mri-in-a-population-based-cohort-with-knee-pain/