Akbar Hojjati Najafabadi, a significant portion of the knee reaction force comes from body weight, and the remaining force is contributed by compression caused by the muscles spanning the knee.

Knee reaction force during gait can vary depending on factors such as walking speed, individual body weight, and biomechanics. Generally, the knee joint experiences a force of approximately 2-3 times an individual's body weight during walking. This can increase up to 4-5 times during more strenuous activities such as running or jumping.

The knee reaction force can be divided into two main components: the vertical ground reaction force, which is related to the support and propulsion of body weight, and the shear force, which is associated with the forward and backward motion during gait.

It is important to note that these values can differ between individuals due to unique factors, such as their anatomy, walking style, and fitness level. Furthermore, the force distribution within the knee joint is complex and influenced by the interplay of various ligaments, muscles, and other soft tissues.

Other factors that can change the knee reaction forces include:

• Activity type: Different activities like walking, running, jumping, squatting, or stair climbing place varying levels of stress on the knee joint and may affect the distribution of forces.
• Speed and intensity: The speed and intensity at which an activity is performed can change the forces acting on the knee. For example, running at a faster pace or performing high-intensity exercises can result in increased stress on the knee joint.
• Technique and biomechanics: An individual's movement patterns and biomechanics can affect the load on the knee joint. Poor technique or alignment during physical activity may lead to increased stress on the knee and other joints.
• Joint and muscle flexibility: Adequate flexibility in the muscles and joints surrounding the knee can help distribute forces more evenly and reduce excessive loading on specific areas.
• Muscle strength and balance: Strong and balanced muscles can help stabilize the knee joint and better distribute forces during physical activity.
• Footwear: The type of footwear worn can impact the forces experienced by the knee joint. Supportive and well-cushioned shoes can help reduce stress on the joint.
• Surface and terrain: The type of surface and terrain where an activity is performed can influence the forces experienced by the knee. Softer surfaces like grass or cushioned tracks can help absorb some impact, while hard or uneven surfaces may increase joint stress.
• Body composition: An individual's body composition, including their weight distribution and muscle mass, can also affect the forces experienced by the knee joint.
• Anatomical differences: Individual anatomical differences such as leg length, alignment of the knee joint, and foot arch type can influence the distribution of forces on the knee.
• Previous injuries and medical conditions: A history of injuries or medical conditions affecting the knee or surrounding structures can impact how forces are distributed across the joint.

The knee reaction force during gait can vary depending on several factors, such as walking speed, individual biomechanics, and overall body weight. However, a commonly cited value for the peak knee reaction force during walking is around 2.5 to 3 times an individual's body weight. This value typically occurs during the stance phase of gait, particularly in the early stance, when the knee joint experiences the highest loads.

Keep in mind that these values are only approximate and can vary significantly between individuals. Factors like walking or running technique, footwear, and any pre-existing knee conditions may influence the actual knee reaction forces experienced during gait.

Reading suggestion:

SIGWARD, Susan M.; LIN, Paige; PRATT, Kristamarie. Knee loading asymmetries during gait and running in early rehabilitation following anterior cruciate ligament reconstruction: a longitudinal study. Clinical biomechanics, v. 32, p. 249-254, 2016.

OBRĘBSKA, Paulina; SKUBICH, Justyna; PISZCZATOWSKI, Szczepan. Gender differences in the knee joint loadings during gait. Gait & Posture, v. 79, p. 195-202, 2020.

ZALEWSKA, Paulina; SKUBICH, Justyna; PISZCZATOWSKI, Szczepan. Gender differences in the knee joint loadings during gait. Gait & Posture, v. 79, 2020.

SCHMITZ, Anne; NOEHREN, Brian. What predicts the first peak of the knee adduction moment?. The Knee, v. 21, n. 6, p. 1077-1083, 2014.

ZHAO, Dong et al. Correlation between the knee adduction torque and medial contact force for a variety of gait patterns. Journal of orthopaedic research, v. 25, n. 6, p. 789-797, 2007.

Good Studies!