# Bone: An Outstanding Composite Material
## 4 Macrostructure
Although only a few important features of the weight-bearing mechanism of the proximal tibia were presented here, the contact mechanism between the femoral and tibial articular surfaces are complex and consist of many unique features, and its biomechanics is not still fully understood [90; 97; 102; 103]. In the case of the ankle, it is expanded to a lesser extent when compared to the upper joint. This occurs since the load of body weight that is transmitted through the lower leg divides itself into two components, which resolve into vertical and horizontal force when it reaches the talus trochlea. The horizontal force will stretch the plantar ligaments and muscles, and the vertical load will be lesser than the actual load transmitted along the long bone [90]. During daily activities, such as normal level walking, the tibofemoral joint experiences high compressive loads around 3 times the body weight (normally expressed as \(\times\)BW), i.e., 2058 N if a 70 kg adult was considered. However, more strenuous activities such as squats can raise the load values for up to 7.3 times the body weight, i.e., 5008 N if the same body weight was considered (see Table 1). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Activity**} & \multicolumn{3}{c}{**Knee Contact Force (\(\times\)BW)**} & \multirow{2}{*}{**Study 1**} & \multirow{2}{*}{**Reference**} \\ \cline{2-2} \cline{5-6}  & \multicolumn{1}{c}{**Medial**} & & & & \\ \cline{2-2} \cline{5-6}  & **1 st Peak** & **2 nd Peak** & & & \\ \hline \hline \multirow{9}{*}{Level walking} & & 3.2 & & In vivo & [104] \\ \cline{2-2} \cline{5-6}  & & 2.8 & & Simulation & [105] \\ \cline{2-2} \cline{5-6}  & & 2.4 & 1 & In vivo & [103] \\ \cline{2-2} \cline{5-6}  & 2.2–2.5 & 2.37–2.51 & Similar & In vivo & [106] \\ \cline{2-2} \cline{5-6}  & & 2.8 & & In vivo & [107] \\ \cline{2-2} \cline{5-6}  & & 3.3 & & Simulation & [108] \\ \cline{2-2} \cline{5-6}  & & 4.0 & & In vivo & [110] \\ \cline{2-2} \cline{5-6}  & & 2.8 & & In vivo & [111] \\ \cline{2-2} \cline{5-6}  & 2 & 1.5 & In vivo & [112] \\ \cline{2-2} \cline{5-6}  & 1.3–1.5 & 1.3–1.5 & 0.8–1.15 & In vivo & [113] \\ \cline{2-2} \cline{5-6}  & 2.8 & & Simulation & [105] \\ \cline{2-2} \cline{5-6}  & 3.3 & & Simulation & [108] \\ \cline{2-2} \cline{5-6}  & 2.9 & & In vivo & [114] \\ \hline \hline \multirow{9}{*}{Stair} & & 2.28–2.5 & 2.28 & - & In vivo & [106] \\ \cline{2-2} \cline{5-6}  & & 2.8 & & In vivo & [107] \\ \cline{2-2} \cline{5-6}  & & 5.3 & & In vivo & [110] \\ \cline{2-2} \cline{5-6}  & & 2.9 & & In vivo & [111] \\ \cline{2-2} \cline{5-6}  & & 5.4 & & Simulation & [109] \\ \cline{2-2} \cline{5-6}  & 2.63–2.81 & 2.8 & - & In vivo & [106] \\ \cline{2-2} \cline{5-6}  & Descending & 3.1 & & In vivo & [107] \\ \cline{2-2} \cline{5-6}  & & 3.3 & & In vivo & [111] \\ \cline{2-2} \cline{5-6}  & 2.09 & - & - & In vivo & [106] \\ \cline{2-2} \cline{5-6}  & & 2.6 & & In vivo & [111] \\ \cline{2-2} \cline{5-6}  & 3.38–7.89 & & In vivo & [115] \\ \hline \hline \multirow{2}{*}{Jogging} & & 3.6 & In vivo & [107] \\ \cline{2-2} \cline{5-6}  & & 7.3 & In vivo & [110] \\ \cline{2-2} \cline{5-6}  & 6.3 & In vivo & [116] \\ \cline{2-2} \cline{5-6}  & 4.7–5.6 & In vivo & [117] \\ \hline \hline \end{tabular}  
* The correct determination of the load applied to the tibia bone would be through the measurement of the forces in in vivo, which is limited and not feasible in healthy subjects or patients with pathology not requiring a total knee replacement. Therefore, in most studies where physiological data were acquired, “kineological techniques”, such as high-speed time camera, force platform, and electromyographic recorder, were used. The results obtained were considered in this article as being in vivo or as close as possible to in vivo data.  
\end{table} 
Table 1: Peak tibofemoral joint compressive forces during several daily activities and expressed as times the bodyweight.