Is treadmill exercise harmful to the knee joints?

From the Guidelines

Treadmill use is generally not harmful to knee joints when used properly and in moderation, as it can actually be beneficial for joint health by strengthening the muscles supporting the knee and improving joint lubrication, as recommended by the 2019 American College of Rheumatology guideline for the management of osteoarthritis of the hand, hip, and knee 1. When using a treadmill, it is essential to take precautions, especially for individuals with existing knee problems.

• Using proper footwear with good cushioning and support is crucial.
• Starting with short, low-intensity sessions and gradually increasing duration and intensity can help prevent knee pain.
• Maintaining good posture with a slight forward lean, avoiding overstriding, and keeping the incline between 1-2% to mimic natural outdoor walking conditions can also reduce the risk of knee injury. The cushioned surface of most treadmills provides better shock absorption than concrete or asphalt, reducing impact forces on the knees, as supported by a study on the criteria and guidelines for returning to running following a tibial bone stress injury, which found that running on a treadmill resulted in reduced peak tibial acceleration compared to running overground 1. However, if knee pain occurs while using a treadmill, it is recommended to reduce speed and intensity or consider alternative low-impact exercises like elliptical training or swimming, as suggested by the treatment of osteoarthritis of the knee guideline, which recommends low-impact aerobic fitness exercises for patients with symptomatic OA of the knee 1. The biomechanical reason treadmills can be knee-friendly is that the moving belt helps promote a midfoot strike rather than a heel strike, distributing impact forces more evenly throughout the lower body. Overall, treadmill use can be a safe and effective way to improve knee health when used properly and in moderation, as part of a comprehensive treatment plan that includes exercise and other interventions, as recommended by the 2019 American College of Rheumatology guideline for the management of osteoarthritis of the hand, hip, and knee 1.

From the Research

Treadmill and Knee Joints

• The provided studies do not directly address the harm caused by treadmills to knee joints.
• However, they discuss the relationship between knee pain, quadriceps and hamstring strength, and exercise 2, 3, 4, 5, 6.
• A study published in 2013 found that strengthening the hamstring muscles in addition to strengthening the quadriceps muscles proved to be beneficial for perceived knee pain, range of motion, and decreasing the limitation of functional performance of patients with knee OA 2.
• Another study in 2014 suggested that understanding the load and stress under the kneecap when executing squats and leg extensions can help perform these exercises better and with less pain while strengthening the quadriceps 3.
• A 2016 study examined the relationships between knee pain status and electromyography (EMG) amplitude of knee muscles during squat and lunge exercises, and found that pain may not be a useful indicator of EMG amplitude or KAM during exercise in knee OA 4.
• A systematic review with meta-analysis published in 2024 found that individuals with knee OA presented with reduced hamstring strength compared to pain-free controls, and that assessing and targeting impairments in hamstring strength and flexibility during rehabilitation may be recommended for individuals with knee OA or PFP 5.
• A 2000 study analyzed the quadriceps muscle control strategy in AKP patients during an isokinetic exercise, and found significant modifications in Vastus Medialis activity compared to the other quadriceps muscles, which can explain the abnormal motion of the patella 6.

Exercise and Knee Pain

• The studies suggest that exercise, such as strengthening the quadriceps and hamstring muscles, can be beneficial for knee pain and function 2, 3, 5.
• However, they also highlight the importance of proper exercise technique and understanding the load and stress on the knee joint to minimize pain and injury 3, 4.
• The relationship between knee pain and exercise is complex, and more research is needed to fully understand the effects of treadmill use on knee joints.

Knee Joint Health

• The studies emphasize the importance of considering the entire knee joint, including the quadriceps and hamstring muscles, when assessing and treating knee pain and disorders 2, 5, 6.
• They suggest that impairments in hamstring strength, flexibility, and morphology can be associated with altered knee biomechanics, pain, and function, and that targeting these impairments during rehabilitation may be beneficial 5.