When your ACL entirely tears, and PCL gets buckled hence your tibia shifts, it's a serious issue. You might be

Although sacroiliac joint dysfunction is usually considered to be the source of lower back and/or leg pain, it can be difficult to diagnose. When the normal mobility of the sacroiliac joint, which joins the triangular bone at the bottom of the spine (the sacrum) to the pelvic, is interrupted, it can produce pain.

• More specifically, sacroiliac joint pain can be caused by either too much or too little movement. Because they can feel so similar, leg pain caused by sacroiliac joint dysfunction might be difficult to distinguish from radiating leg pain caused by lumbar disc herniation (sciatica). The most common causes of SI joint dysfunction are excessive or insufficient mobility.

• Excessive movement in the sacroiliac joint (hypermobility or instability) can make the pelvis feel unstable and result in pain.

• Excessive mobility generates pain in the lower back and/or hip that can spread into the groin, whereas lack of movement (hypomobility or fixation) causes muscle tension, discomfort, and a loss in mobility.