First, please see the video below for better understanding.

1. Patella/quadriceps tendon problems (Tendinopathy/Tendonitis)

As explained in the video (03:55), if the center of the body moves forward due to weak core muscles, the hip muscles can't function properly and the quadriceps muscles start to compensate and get tight. This tightness, in turn, is likely to pull the patella/quadriceps tendons upwards and this puts a prolonged stretch on the tendons, which will gradually compromise their elasticity. According to studies, tendon problems such as tendinopathy and tendonitis are prone to occur when there is a combination of the compressive(compression against the bone) and tensile(stretching force) loads. Therefore, it is important to strengthen the core to improve the body balance as well as restoring the elasticity of the tendons.

2. Pes anserinus (Tendinopathy/Tendinitis/Bursitis)

Similar to the first condition, this is also a tendon issue. The main cause is the same. Once the muscles attached to the tendons get tight and start to pull on them, the tendons get stressed due to the compressive and tensile loads. If the friction and stretching force causes inflammation, it will be 'tendinitis' and if it affects the bursa, it will be 'bursitis'. The tendinitis can become 'tendinopathy' when the inflammatory response becomes less active and turns into a scar tissue (degenerative changes).

This second condition is also associated with the alignment of the pelvis and hip joints. If the hip muscles, that are supposed to hold the thigh bone from the back, become weak, the thigh bone not only moves forward but also rotates inward. This internal rotation of the thigh bone puts a stretching force on the inside of the knee, which can lead to problems like around that area.

Moreover, when the arch of the foot is lowered, the ankle collapses inward. Then, the knee is also easy to turn inward. I'll go into more detail when we talk about walking patterns.

3. Chondromalacia/meniscus tear

Surprisingly, chondromalacia is also to do with the quadriceps tightness. When the tightened thigh muscles pull the patella up, the cartilage between the patella and the femur gets rubbed against each other as shown in the image above.

Also, when the thigh bone tilts forward or turns inward as aforementioned, the probability of damage to the cartilage under the femur increases due to the twisting force. This is more likely to occur if there is an excessive side shift observed in your pelvis during walking.

For example, please see the image below. If you think about the pelvis moving more toward the leg on the ground, the thigh bone relatively goes more inward. This will also increase the risk of knee injury like ligament tear by creating a stronger twisting force.