Knee Osteoarthritis: The Impact of Weight Loss and Strength-to-Weight Ratio

Knee osteoarthritis (OA) is one of the most common causes of pain and disability among older adults. It results from the degeneration of the cartilage within the knee joint, leading to inflammation, pain, stiffness, and reduced mobility. Given the weight-bearing nature of the knee joint, body weight plays a significant role in both the onset and progression of knee OA. In this blog, we will explore the clinical benefits of weight loss in managing knee OA, the influence of strength-to-weight ratio on knee function, the top exercises for managing symptoms, and available clinical management options.

The Role of Weight in Knee Osteoarthritis

The knee is a major weight-bearing joint, and studies show that with every pound of body weight, the knee experiences approximately four pounds of pressure during walking. Thus, excess weight amplifies the stress on the knee, accelerating the wear and tear on the cartilage. Research suggests that even modest weight loss can lead to significant improvements in knee OA symptoms.

In a study published in Arthritis & Rheumatism, Messier et al. (2005) found that a 10% reduction in body weight led to a 50% reduction in knee pain in individuals with OA. Losing weight not only decreases the pressure on the knees but also reduces inflammation in the joint. Fat tissue produces pro-inflammatory substances such as cytokines, which can exacerbate the inflammatory process in osteoarthritis. Thus, weight loss can mitigate both mechanical stress and biochemical inflammation.

Strength-to-Weight Ratio: A Key Factor in Knee Health

While body weight is important, the strength-to-weight ratio also plays a crucial role in knee osteoarthritis. This ratio refers to the balance between muscle strength (particularly in the quadriceps and hamstrings) and body weight. Stronger muscles support the knee joint, absorbing shock and reducing the load on the cartilage. Individuals with weak muscles and higher body weight place more stress on their joints, which can worsen OA symptoms and increase the risk of progression.

A study by Segal et al. (2009) published in Osteoarthritis and Cartilage emphasised that weaker quadriceps muscles are associated with worse knee pain and function, irrespective of body mass index (BMI). This underscores the importance of not just losing weight but also building strength to improve the overall health and function of the knee joint.

Top Exercises for Managing Knee Osteoarthritis

Exercise is a key component of OA management, helping to strengthen muscles around the knee, increase flexibility, and improve mobility. Here are four top exercises recommended for individuals with knee OA:

1. Quadriceps Strengthening (Straight Leg Raises): Strengthening the quadriceps is crucial to reducing stress on the knee joint. To perform, lie flat on your back, lift one leg straight up while keeping the other knee bent, and hold for a few seconds before lowering.
2. Hamstring Curls: This exercise strengthens the hamstrings at the back of the thigh, helping to balance the support for the knee. Stand and bend your knee to bring your heel toward your buttocks. Hold for a moment and slowly lower the leg.
3. Clamshells: This exercise targets the hip abductors, muscles that are important for stabilizing the knee. Lie on your side with knees bent, then lift your top knee while keeping your feet together. This movement opens the hips and strengthens the gluteal muscles.
4. Single leg, Leg Press: A great and functional exercise – everything we do is usually one leg at a time – walking, running, stairs etc. So, train this way! Quadriceps, Gluteal muscles and Hamstrings are targeted here and the weight can be adjusted. We should be aiming to lift our body weight with one leg.  

Clinical Management Options for Knee Osteoarthritis

In addition to exercise and weight management, various clinical options are available for managing knee OA:

1. Steroid Injections: Corticosteroid injections can provide short-term pain relief by reducing inflammation within the knee joint. These injections are typically used in individuals with flare-ups of pain but are not recommended for frequent use (more than three in one year) due to potential side effects such as cartilage damage with repeated use, although only mild the effects are still there and better options exist.
2. Hyaluronic Acid Injections: Hyaluronic acid is a naturally occurring substance that lubricates joints. These injections aim to improve the viscosity of the joint fluid, providing better cushioning and reducing pain. Clinical trials, such as those reported by Altman et al. (2015) in The Journal of Clinical Rheumatology, suggest that hyaluronic acid injections may benefit patients with mild-to-moderate OA.
3. Arthrosamid Injections: A newer treatment, Arthrosamid, consists of a hydrogel that acts as a cushion and lubricant inside the knee. This injectable hydrogel integrates with the synovial tissue, providing longer-lasting pain relief and joint function improvement. Early studies suggest promising results for those with moderate to severe OA, as outlined in a 2022 study published in Cartilage.

Diagnostic Ultrasound in Osteoarthritis Management

Diagnostic ultrasound plays an essential role in both diagnosing and managing knee osteoarthritis. It allows for the real-time visualisation of soft tissues, including cartilage, synovium, and ligaments. Ultrasound is particularly useful in detecting joint effusion, synovial hypertrophy, and crystal deposition, which are key factors in OA assessment. Moreover, it is a helpful tool in guiding injections, such as corticosteroids or hyaluronic acid, ensuring accurate placement and improving treatment efficacy.

Ultrasound is often favoured over MRI due to its cost-effectiveness, lack of radiation exposure, and ability to provide dynamic imaging during joint movement. In a review by Delle Sedie et al. (2010) published in Rheumatology, ultrasound was highlighted as an increasingly important tool in OA management due to its ability to assess disease progression and guide interventions.

Conclusion

Knee osteoarthritis is a multifactorial disease where body weight, muscle strength, and biomechanical factors play critical roles in its development and progression. Weight loss can significantly reduce the stress on the knee joint, while strengthening exercises improve muscle support around the joint. In conjunction with these lifestyle modifications, clinical management options such as steroid, hyaluronic acid, and Arthrosamid injections offer valuable pain relief and improve joint function. Diagnostic ultrasound provides an essential tool for both diagnosis and treatment guidance, further enhancing the management of knee osteoarthritis.

References

1. Messier, S. P., Loeser, R. F., Miller, G. D., et al. (2005). Exercise and dietary weight loss in overweight and obese older adults with knee osteoarthritis: The Arthritis, Diet, and Activity Promotion Trial. Arthritis & Rheumatism, 50(5), 1501-1510.
2. Segal, N. A., Glass, N. A., Felson, D. T., et al. (2009). Effect of quadriceps strength and proprioception on risk for knee osteoarthritis. Osteoarthritis and Cartilage, 17(6), 547-553.
3. Altman, R. D., Manjoo, A., Fierlinger, A., et al. (2015). The mechanisms of action for hyaluronic acid treatment in the osteoarthritic knee: A systematic review. Clinical Rheumatology, 34(10), 1575-1585.
4. Delle Sedie, A., Riente, L., Bombardieri, S. (2010). Limits and perspectives of ultrasound in the diagnosis and management of rheumatic diseases. Rheumatology, 49(7), 1410-1414.