Available online 29 November 2022

Author links open overlay panelAbstractBackground

We investigated intramuscular fat (IMF) in quadriceps femoris (QF) and hamstring muscles in the middle-aged women with knee osteoarthritis (KOA). We also examined the relationship between muscular infiltration of QF and hamstring muscles and muscle architecture and physical performance of the women with KOA.

Methods

In this cross-sectional study, 72 women were included. Body muscle and fat mass were measured by BIA, isometric muscle strength was evaluated by hand-held dynamometer. IMF and muscle architecture were calculated from rectus femoris (RF), vastus intermedius (VIM), vastus lateralis (VL), vastus medialis (VM), biceps femoris (BF), semitendinosus (ST) and semimembranosus (SM) using B-mode ultrasonography. KOA-related symptoms and functions were assessed with KOOS. The functional performance assessments were evaluated with Stair Climbing Test, 20-Meter Walking Test.

Results

Women with KOA had more IMF in RF, VIM, VL, VM and BF, ST, SM muscles compared to the healthy women. Pennation angles decreased as the IMF in the RF, VM, BF and ST decreased. As the IMF of the RF and VM increased isometric knee extensor strength decreased and KOOS symptom score, pain score and ADL score increased in women with KOA. Walking and stair climbing speed deteriorated as the IMF in RF, VIM, VM, BF increased in the middle-aged women. As the IMF in BF increased isometric knee flexor strength decreased and KOOS scores increased. Physical performance scores deteriorated as the IMF in BF increased in middle-aged women with KOA.

Conclusion

IMF in QF and hamstring muscles were higher in the middle-aged women with KOA group compared with that in the healthy group. Weakness of the QF and hamstring muscles may due to the changes in architectural properties of muscle depending on muscular infiltration. IMF in knee muscles is an important determining factor in performance and physical function of middle-aged women with KOA.

Introduction

Knee osteoarthritis (KOA) is more important than other types of osteoarthritis, not only because of its high prevalence, but also because it occurs in earlier age groups of obese women, especially younger age groups. Low quadriceps femoris (QF) muscle strength is a risk factor for KOA development in women and they have a higher risk of KOA than men, and the relative risk in women is 2.6 times higher than in men [1]. Decline in muscle strength is commonly attributable to a loss of muscle tissue, but this assumption does not fully explain the extent of muscle weakness seen in people with KOA. Changes in muscle composition may be more important than muscle size and thickness in explaining muscle weakness. In this regard, Kumar et al. [2] found that the muscle thickness of the patients with KOA was the same as the healthy control group, while QF muscle strength of the KOA group was less and the intramuscular fat infiltration of this muscle was more than healthy group. Excess muscular fat infiltration may cause an alteration in contractile fiber pennation angle, thus resulting in an unfavorable mechanical angle and a concomitant reduction in force production [3]. Although osteoarthritis is diagnosed and defined as the loss of hyaline cartilage within the joint, disease-related muscle disorders may be the primary underlying cause of functional disorders, and muscle dysfunction may actually precede cartilage degeneration. For this reason, KOA should not be considered as a disease of cartilage tissue and related muscle problems should be considered in the clinical management of the disease [4]. Evaluation of fat infiltration and its association with measures of muscle architecture and muscle capacity can provide a better understanding of the pathophysiology of KOA. Higher muscle infiltration particularly in the gastrocnemius, was related to worse physical performance [5]. To date, despite the important role of musculature in mobility and physical functioning and the negative impact of fat infiltration in the muscles, relatively little work has been done to assess the effect of muscular fat tissue around the knee on strength and mobility performance in patient with KOA.

An in-depth understanding of the effect of skeletal muscle fat infiltration on the symptoms and musculature associated with KOA may help explain widespread muscle weakness. The aim of this study was to evaluate the IMF in muscles around the knee in middle-aged women with and without KOA, to compare the two groups, and to investigate the relationship between IMF infiltration and skeletal muscle architectural features. The other aim of our study is to investigate the relationship between the intramuscular fat ratio of the QF and hamstring muscles and muscle strength and physical performance in middle-aged women with KOA.

Section snippetsMaterials and methods

It is a cross-sectional study was conducted between April 2020–June 2021 in the outpatient clinic. Ultrasonographic assessments and post-image analyses were performed in Department of Radiology. The current cross-sectional study was reported following the “Strengthening the Reporting of Observational Studies in Epidemiology” (STROBE) [6].

All patients had apparent radiographic changes in the bilateral or unilateral knees indicative of OA and were diagnosed as Kellgren–Lawrence(K-L) grade≥2. The

Results

Seventy-two volunteers (36 women with KOA, 36 women without KOA, mean age 49.21 ± 8.13 years) participated in the study. Clinical characteristics of all subjects are shown in Table 1. No significant differences were observed with respect to age, BMI, skeletal muscle mass and skeletal muscle index between the groups. Fat mass were significantly higher in the KOA group than in the healthy group, isometric knee extension and flexion strength were significantly higher in the healthy group than in

Discussion

In this study, we compared the IMF in QF and hamstring muscles in the middle-aged women with and without KOA. IMF in QF and hamstring muscles was higher than the healthy control group. And also, PA of the muscles increased as the IMF in RF, VM and BF, ST increased. As the IMF of QF and hamstring muscles increased, the physical performance and walking speed of the patients also deteriorated in the middle-aged women with KOA.

IMF in QF and hamstring muscles of women with KOA included in our study

Conclusions

In conclusion, IMF in the QF and hamstring muscles were higher in the middle-aged women with KOA group compared with that in the healthy group. And also, weakness of the QF and hamstring muscles in women may due to the changes in the architectural properties of the muscle depending on the intramuscular fat ratio. IMF in the knee muscles, especially in the VM and BF muscles, is an important determining factor in the performance and physical function of middle-aged women with KOA. These results

Ethical approval

This study was approved by the Ethical Committee of Clinical Research of Suleyman Demirel University, Faculty of Medicine on 12 March 2020 (Approval Number: 79).

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Data availability

The data that support the findings of this study are available on reasonable request from the corresponding author (MK). The data are not publicly available due to their containing information that could compromise the privacy of research participants.

Declaration of competing interest

Merve Karapınar, Veysel Atilla Ayyıldız, Meriç Ünal and Tüzün Fırat declare that they have no conflict of interest.

Acknowledgements

The authors thank all of the participants who included in the study.

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