Effect of Core Versus Hip Strengthening on Knee Function in Adults With Knee Osteoarthritis: A Randomized Controlled Trial

Abstract

Background Osteoarthritis (OA) is a prevalent condition characterized by joint pain, functional limitation, and reduced quality of life, particularly affecting older adults, with a higher prevalence in women. OA impacts daily activities, such as walking, climbing stairs, and driving, and is one of the leading causes of pain and disability worldwide. This further affects a person's ability to carry out their activities of daily living and reduces quality of life as a consequence. Exercise remains a core recommendation for managing knee osteoarthritis (OA), and structured exercise programs have been shown to improve knee-related and overall health outcomes. Existing literature supports the effectiveness of core stability and hip strengthening exercises when added to knee strengthening for the management of OA knee. However, there is limited research comparing these two approaches. This study aims to evaluate the effect of supervised core stability versus hip strengthening exercises, alongside conventional occupational therapy, on improving functional outcomes, mobility, and strength in OA knee patients. Methodology Patients diagnosed with unilateral osteoarthritis of the knee, grades 1, 2, and 3 according to the Kellgren-Lawrence( KL) grading system, managed conservatively, with no history of trauma or surgery of symptomatic knee after taking approval from the Institutional Ethics Committee of Seth GS Medical College and KEM Hospital were categorized into group A (Core) and group B (Hip) using convenient sampling. A total of 34 patients, both males and females, between 40 and 60 years of age were allocated into group A or B, and were evaluated at baseline, 2 weeks, 4 weeks, and 6 weeks on the knee osteoarthritis outcome score (KOOS), 30-second chair stand test, and the modified Oxford manual muscle grading system. Both groups were given conventional occupational therapy treatment. Results Both the Core and Hip groups showed a statistically significant improvement in KOOS, muscle strength of knee flexors and extensors, and the number of repetitions on the 30-second chair stand test. When the Core and Hip groups were compared, the improvement in these parameters was statistically insignificant. Conclusion Both hip and core strengthening exercises are equally effective in improving muscle strength, pain, quality of life, and activities of daily living, leading to improvement in KOOS scores in patients with OA knee.

Keywords: core stability; functional outcome; hip strengthening; knee osteoarthritis; occupational therapy.

Figure 1. Intra-group analysis of group A (Core)

The Friedman test results reveal statistical significance at baseline, two weeks, four weeks, and six weeks for knee flexors, knee extensors, and number of repetitions (p < 0.05). However, pairwise comparison using Bonferroni correction for the variables Knee Flexors and Knee Extensors did not identify specific time points where these differences reached statistical significance. The Friedman test results are statistically significant at baseline, two weeks, four weeks, and six weeks for components of the knee injury osteoarthritis outcome score (KOOS) scale that is pain, symptom, activity of daily living (ADL), sport/recreation, quality of life (QOL), KOOS average (p < 0.05).

Figure 2. Intra-group analysis of group B (Hip)

The Friedman test results reveal statistical significance at baseline, two weeks, four weeks, and six weeks for knee flexors, knee extensors, and number of repetitions (p < 0.05). However, pairwise comparison using Bonferroni correction for the variables knee flexors and knee extensors did not identify specific time points where these differences reached statistical significance. The Friedman test results reveal statistically significant at baseline, two weeks, four weeks, and six weeks for components of the knee injury osteoarthritis outcome score (KOOS) scale that is pain, symptom, activity of daily living (ADL), sport/recreation, quality of life (QOL), KOOS average (p < 0.05).

Figure 3. KOOS scale pain component at baseline, two weeks, four weeks, and six weeks

Both the Hip and Core groups performed similarly with respect to the pain component of the knee injury and osteoarthritis outcome score (KOOS); that is, 0-2 weeks and 2-4 weeks did not show statistically significant improvement. From the fourth week onward, the pain score improved in both groups, which is evident from the fact that there was statistically significant improvement when pain scores were compared between 4-6 weeks and 2-6 weeks. Both groups showed a statistically significant improvement when scores of baselines were compared with the sixth week score. The improvement in scores when compared in 0-2 weeks and 2-4 weeks was not statistically significant.

Figure 4. KOOS scale symptom component at baseline, two weeks, four weeks, and six weeks

Both the Hip and Core groups performed similarly. In 0-2 weeks and 4-6 weeks, there was no statistically significant difference in improvement in both groups on the knee injury and osteoarthritis outcome score (KOOS). In all other timelines, that is, 2-4 weeks and 2-6 weeks, there was a statistically significant improvement in scores. The scores at 0-4 weeks and 0-6 weeks also showed a significant difference in both groups.

Figure 5. KOOS scale QOL component at baseline, two weeks, four weeks, and six weeks

On the knee injury and osteoarthritis outcome score (KOOS) scale, quality-of-life (QOL) scores of both groups did not show improvement when compared at 0-2 weeks. However, when baseline scores were compared to four weeks and six weeks, there was a statistically significant difference observed. Both groups showed statistical differences in scores at 2-4 weeks, but only the core group showed an improvement at 4-6 weeks. This means that the Hip group remained static. When scores of both groups were compared for 2-6 weeks, there was a statistically significant difference observed.

Figure 6. KOOS scale ADL component at baseline, two weeks, four weeks, and six weeks

In the knee injury and osteoarthritis outcome score (KOOS) scale, activities of daily living (ADL) component scores, only the Core group showed significant improvement in scores in the first 2 weeks, i.e., 0-2 weeks. Both groups showed statistically insignificant differences when scores were compared at 2-4 weeks. Both groups showed significant improvement when scores were compared at 4-6 weeks and 2-6 weeks. Both the groups’ scores, when compared from 0-4 weeks and 0-6 weeks, there was a statistically significant difference observed.

Figure 7. KOOS scale sports/recreation component at baseline, two weeks, four weeks, and six weeks

Both the Hip and Core groups performed similarly with respect to the sports and recreation component of the knee injury and osteoarthritis outcome score (KOOS), that is, 0-2 weeks and 2-4 weeks did not show statistically significant improvement. From the fourth week onward, sports and recreation scores improved in both groups, which is evident from the fact that there was statistically significant improvement when scores were compared between 4-6 weeks and 2-6 weeks. Both groups showed statistically significant improvement when scores of baselines were compared with the sixth week score, i.e., 0-6 weeks. The improvement in scores when compared in 0-2 weeks and 2-4 weeks was not statistically significant.

Figure 8. KOOS scale KOOS average component at baseline, two weeks, four weeks, and six weeks

In the knee injury and osteoarthritis outcome score (KOOS), the KOOS average component, a 0-2 weeks average score improvement was seen in the Core group but not in the Hip group. Later, there was improvement in the 2-4 weeks in the Hip group but not in the Core group. This means that the Core group showed improvement at 0-2 weeks, but later, it remained static or slow. At 4-6 weeks, both groups were comparable, with similar results in both groups. Also both groups showed a statistically significant difference when scores were compared from baseline to the fourth week and baseline to the sixth weeks; that is, 0-4 weeks and 0-6 weeks respectively.