Doing the same actions or exercises regularly, the brain and body can adapt in such a way that if there are any week points muscles can be repurposed to protect joints and make the regular movements as easy and efficient as possible.
Learning new movements, or restarting new movements or exercises that haven't been done since, say the onset of an injury, holes can come up in the algorithms the brain uses to operate the body.
I haven't run for about 20 years after a motor cycle accident damaged my knee.
I didn't get the knee treated, instead preferring to see if I could fix it myself. And while the knee has gotten better, proper function has been elusive. For example, I haven't been able to run without any knee or hip pain for that entire time.
I've experimented, but my solution for each problem has always uprooted another problem.
It wasn't until recently that I started running again (more like hobble for a bit then walk for a bit) that I seemed to have gotten to the root of the problem and gotten closer to the optimal algorithms for that side of my leg while running. In the process one of the things that I uncovered was a seeming link between the gluteus maximus, the portion that attaches to the IT band, and the sartorius.
The sartorius could be thought of as one of the long thigh muscles.
At its uppermost end it attaches to the front point of the hip crest (the ASIC or Anterior Superior Iliac Spine).
From there is runs downwards and rearwards along the inside of the thigh, angling behind the bulk of the rectus femoris and vastus medialis before bending forwards just below the bump of the knee to attach to the inside surface of the tibia along with two other "long thigh muscles", the gracilis and the semitendinosus.
At this shared insertion these three muscle tendons form a goose foot shaped structure called the pes anserinus (which is latin for goose foot).
These three muscles all attach to prominent "corner points" of the pelvis.
Where the sartorius attaches to the ASIC,
the gracilis attaches to the pubic symphysis (or pubic bone) while
the semitendinosus attaches to the ischial tuberosity or sitting bone (the bones on either side of and just rearwards of the anus that you can feel when sitting down.)
Where the three pes anserinus muscles run separate for most of their length before joining at the tibia, the corresponding structure that runs along the outside of the thigh, the IT band, is joined for most of its length.
The IT band runs down the outside of the hip and thigh from the iliac crest to the top of the tibia.
Two muscles that attach to it are the tensor fascia latae and the superficial fibers of the gluteus maximus.
One way to model or think of the IT band is as two separate tendons that are joined along their length. The front tendon is worked on by the tensor fascia latae. The rear tendon is worked on by the superficial fibers of the gluteus maximus.
These muscles also attach to prominent corner points of the pelvis.
Like the sartorius, the tensor fascia latae attaches to the ASICs and from there passes downwards and rearwards before attaching to the front edge of the IT band near the greater trochanter, the "bump" of the thigh bone that you can feel half a hand span below the crest of the hip.
The gluteus maximus attaches to the PSIC (the posterior superior iliac crest or the rear part of the iliac crest) and runs forwards and downwards to attach to the rear edge of the IT Band.
Trying to match strides while running so that my left knee and hip felt like my right, at some point I experienced some slight releases in my knee, like material tearing.
One thing that may happen when the brain uses other algorithms to run the body after an injury is that temporary connective tissue structures build up to support the new movement patterns. These could be thought of as scaffolding. Ideally they are temporary in nature.
My thoughts (and hopes) where that these little tears were just indications that connective tissue scaffolding was being disassembled.
I carried on running and my knee felt fine. However, later on, after a stretch and a relaxation my knee started to tighten up. More precisely it felt like my outer calf and or outer hamstring tightened up.
I've written elsewhere that in the case of the outer hamstring tightening it may be that the outer calf isn't activating or vice versa and so activating the muscle that is relaxed could conceivably release the tension (said tension be to help protect the knee joint.)
That wasn't the case this time. I put up with it for the rest of the day and took a long walk before my next run.
Later on found that focusing on heel and outer foot stabilization sometimes helped.
Running again the next day, or I should say jogging for short distances then walking for longer distances before jogging again, I experienced a different sort of slight release in the knee.
This series of light tears (or what felt like it) was towards the front inside of my knee below the knee cap. So I stopped to walk.
There's not much in the way of muscle near the bottom of the front face of the knee. The only muscle I could think of that was close and that might be remotely helpful was the pes anserinus muscles (Sartorius, gracilis, semitendinosus).
I tried to run again but with my pes anserinus muscles activated. I activated or tried to activate these muscle by creating a forwards and upwards pull on the inside of the top of the tibia. That seemed to help.
Because the sartorius attaches to the ASIC, I was also cognisant of creating an upwards pull on my ASICs. The idea of this was to anchor the upper end of the sartorius.
That helped a little.
After my next few runs I continued to experience tightness at the back of the knee. But playing with muscle control while walking and then running, I found that I could run with the my knees feeling quite sturdy.
I wasn't hiding from pain or letting endorphins or the heat of running dampen pain. Instead I was trying to use technique to keep my knee safe.
Whenever I lost technique or felt my knee beginning to give way then I began walking again.
While walking I studied my knee and the muscles that acted on it to determine what I needed to change to make my knee feel safe again.
Continuing with another bout of running I got the sense that my inner knee needed some stress relief. It felt like I needed to rotate my thigh and shin outwards slightly.
The outward rotation seemed to come about by using the superficial portion of my gluteus maximus. And that seemed to help.
If you try the shin rotation exercises in shin rotations and heel stability you may notice that while rotating your shins outwards you may find more tension along the outside of the knee along with greater pressure along the outer edge of the foot.
While rotating your shins inwards you may find more tension along the inner knee and greater pressure along the inner edge of the foot.
Then there's a middle or neutral position where the inside and outside of both the knee and the foot feel roughly equal in tension and pressure.
While running I found that maintaining having my shin just slightly externally rotated during heel strike felt most comfortable on my knee.
Now I've had trouble with my left side gluteus maximus muscle for a while.
Doing Pigeon Pose Glute Stretch with the shoulder on my front foot side pressing towards my front foot, when pressing the edge of the foot strongly into the floor with right leg forwards I can feel the gluteus maximus activating. With my left leg forward, not so much.
One of the other sensations that I experienced while comparing my left and right legs in pigeon pose was that I could "feel" my right hip bone, my good side, particularly at the ASIC and PSIC. My left side, not so much.
This seeming failure of my gluteus maximus to function also had a noticeable affect when I first experimented with a heel strike while barefoot running .
I experimented briefly withbarefoot heel strike running about a year ago.
Walking I found I didn't have any problem with a barefoot heel strike. When running I found that my left knee tended to cave inwards. And it seemed to be due to a failure of my gluteus maximus.
It would function if I payed attention to alignment, but I couldn't keep it up for long. But when I could maintain it, using a heel strike while running barefoot felt fine.
When the knee is straight the shin cannot rotate relative to the thigh.
Because of the way the sartorius passes behind the knee before attaching to the inside of the top of the tibia, when the knee is straight the sartorius creates a forward pull on the back of the inside of the knee causing external rotation.
When the knee is bent the sartorius, along with the other pes anserinus muscles, can rotate the shin inwards relative to the thigh.
After some more runs, the feeling I had, was that the inside of my knee was "gapping" hinging open slightly and adding tension to the sartorius seemed to help to prevent this.
This was provided I had enough external rotation and that I didn't lose this external rotation during the heel strike.
When the knee is slightly bent during the heel strike portion of the stride while running or (as in my case, jogging), the sartorius can create an internal rotation force on the tibia, assuming the hip bone is stable and assuming the knee is only slightly bent.
To prevent gapping, the sartorius may also create an upwards pull on the inside of the top of the tibia helping to prevent the inside of the tibia from spreading apart from the inside of the femur.
For the sartorius to be able to carry out this function, the shin needs to have an external rotation force acting on it to counteract the internal rotation that the sartorius tends to create.
While the shin is locked to the femur when the knee is straight, it can rotate relative to the femur if the knee is bent.
An interesting thing about the IT band (which attaches to the tibia) is that it seems to rotate the shin and thigh together whether the knee is bent or straight. (I could be wrong on this, but my current experiments seem to indicate that this is the case.)
This could mean that activating the superficial fibers of the gluteus maximus is sufficient to rotate shin and thigh together, even if the knee is slightly bent.
Note that the vastus lateralis may also have to activate so that the IT band has enough tension to pass rotational force from the gluteus maximus to the tibia.
Now even if that isn't the case, the deep fibers of the gluteus maximus attach to the back of the femur and they, when active can rotate the thigh externally. When active, these fibers expand and this may make it easier for the superficial fibers of the gluteus maximus to activate, because they have had some slack removed.
In either case, for myself, while jogging, I found that I needed a slight amount of external rotation of the thigh relative to the pelvis for the heel strike. And it felt like some part of the gluteus maximus was causing that external rotation.
This external rotation may have given the stability my sartorius needed to work against to prevent gapping along the inside of my knee.
In any case, I found that I no longer got the light tearing sensation near the front inside edge of the knee nor the sense of inner knee gapping.
Now I've been running for about a week and after each run I did find that my knee tightened up a little. So each time alot of my "running" session included long periods of walking to loosen up.
During one of my walks I played with activating the inner thigh muscles to de-slacken the sartorius.
For the IT Band, taking out the slack is relatively simple. Activate the vastus lateralis.
For the rectus femoris, slack can be taken out by activating the vastus intermedius (over which it runs.)
With the sartorius, the answer isn't so simple.
Some slack may be removed from the sartorius by activation of the vastus medialis. However, it seems that it is more prone to activation is the inner thigh as a whole is relatively active, including the vastus medialis muscle.
For me it still helped to use gluteus maximus to externally rotate the thigh just enough. Then I found that inflating the inner thigh also helped.
But of course, on the days that followed I still had problems.
Going even deeper, I knew that activating the tibialis anterior can be helpful with alleviating IT band knee pain, particularly while squatting. I then learned (or re-learned) that the peroneus longus muscle also has IT band connections.
Where the tibialis anterior attaches more to the front fibers of the IT band (which relates to the tensor fascia latae) the peroneus longus attaches more to the rear fibers (which relate to the gluteus maximus).
And so I played with activating both the tibialis anterior and the peroneus longus to anchor my IT band to see if that helped my superficial gluteus maximus.
Note that both of these muscles can be activate by the simple expedient of stabilizing the heel. (For some tips on heel stabilization read Shin rotations and Heel Stability)
Playing with peroneus longus and tibialis anterior activation also helped when dealing with after run knee tightness.
My jogging stride is, currently, fairly short, and I found that stabilizing the heel on heel strike is quite helpful. No pain, no "tearing" and relatively comfortable running.
An interesting thing is that about a year ago I finally read about how the IT band may be designed as an energy storage device, basically an elastic, for more efficient running.
For a regular elastic band to store energy you have to pull create two fixed endpoints.
By stiffening the heel prior to impact, could actually help to anchor the bottom end of the IT band, creating one fixed endpoint. Body weight pressing down via the lumbar spine into the back of the pelvis could help to create the other fixed end point.
So in my recent runs I experimented with barefoot heel strike jogging for short distances. It actually felt quite comfortable. Putting shoes back on I worked at creating a solid heel strike despite my relatively soft trainers.
If you've ever watched pole vaulters or high jumpers, my running felt like the way their run ups looked.
Each stride I tried to come down on a stiffened heel.
I still wasn't running super fast or going long distances, but my stride felt noticeably easier and my running lighter.
A year ago when I tried this technique my knee tended to cave inwards, and even then I realized the problem was with the superficial glutes. Maybe sartorius needed to be active so that my glutes could work.
Now while I stiffen my heel during heel strike, currently it feels better to keep my forefoot relatively relaxed, or rather to do it's own thing during heel strike. But, now that my sartorius and glute max are working together I have began to play with varying shin rotation during or after heel strike to see how best to utilize my forefoot. A slight inwards rotation seems to allow me to press off strongly with the inner edge of my forefoot at the tail end of my stride.
I'm not positive I have the complete answer yet, I still have a lot more running to do, but after 20 years of not running my bouts of running are gradually getting longer and rather than knee or hip pain being the issue it's cardiovascular. And that's easy to work on with practice. But when dealing with pain or poor function, I'm finding its not so much practice that matters, but what I practice.
After running for about two weeks, for my latest run I seemed to find a shin rotation relative to my thigh that felt relatively comfortable. As a result I could then vary the rotation of my thigh relative to my pelvis while maintaining the relative rotation of my shin to my thigh.
What I found was that swinging a leg forward I could position my forward swinging thigh so that it was neutral relative to my direction of travel. Then for each stride I turned my pelvis relative to my thigh.
With my right foot back I could begin to turn my pelvis to the left so that the right side of my pelvis moved forwards. This had the same effect as rotating my thigh externally relative to my pelvis. But as an added bonus, the action of turning my pelvis seemed to help swing my foot forwards. It is as if the turn of my pelvis transmitted momentum to my hip joint which then transmitted momentum to my leg.
I was still landing on my heel (and making my heel stable as I landed that foot) but because I was turning my pelvis using my abs, that may have helped to stablize my hips, particularly the ASIC of the forward leg so that the sartorius (and the rectus femoris and the tensor fascia latae) of that leg had a stable anchor point.
My running stride felt relatively effortless and light as a result.
If you are interested in learning more about how to feel and control your leg muscles, Sensational Leg Anatomy includes a series of videos each teaching simple muscle control techniques. Each video focuses on a particular muscle or set of muscles and the whole series teaches you to feel and control the major muscles of the legs from the hip bones down to the toes.