Image Processing detect human joint without any external tools

I am currently doing a project about cycling kinematics analysis using MATLAB R2019b. However I am not so familiar with using MATLAB to code the algorithm to detect the human joints. I will not use any external tools to help on the detection even the video will be import to MATLAB which means it is not a live video. So I need help on having the source code of detecting the human joint when they are cycling. The code should help me to detect the hip, knee and ankle joints. After detect these three joints, the point detected will be connect and calculate the angle. Other than that, the code should not breaking down the video into frame to do detection or after calculate the angle it is able to play all the frames with angle calculated in video. Thank you for your help. Have a nice day. Hope to listen good news from you soon.