There are three tendons that pass around the front of the knee on the inside, one hamstring, semimembranosus, the longest muscle in the body, Sartorius, and Gracilis which doesn’t know if it is a hamstring or an adductor so does a bit of both.
Sometimes referred to as “goose foot” pes anserinus arises from the three-pronged conjoined tendon which inserts onto the inside of the tibia. The tendons have to slide and glide across the bone on each step. There is a fluid filled sack called a bursa which takes the friction, but if the tension increases it can become inflamed and painful.
It is one of those issues which build up rather than suddenly come on. It is sore and tight to use the knee and typically is felt in the morning then eases up. However, when you start to run it is painful and gets worse.
The causes are an increased tension in the tendons as they wrap around the shin bone. The commonest is an increase in tension of the medial hamstring – semitendinosus. This can be the result of issues in the pelvis and sacro-iliac joints.
An alteration in biomechanics which allows the leg to internally rotate or the foot to turn out more will increase the amount the tendons have to wrap around the bone and increase the friction. This can be caused by tight calf muscles, weak gluts and tight hip flexors/illiotibial band (ITB).
Local treatment is ice and anti-inflammatories as well as stopping doing what irritates the bursa. This is one of those issues where stopping running as soon as you feel it becoming sore can be a big time saver. This helps prevent it becoming really inflamed and chronic. It is a difficult area to rest as you cause friction on every step, but stopping running will give it a chance.
There is a lot we can do for this from both the inflammatory aspect as well as mobilising the often very sticky tendons and bursa and of course sorting out the reasons why you are getting the problem to start with.