Thursday, September 19, 2013

Medial Knee Pain - Pes Anserine Bursitis

In this blog we’ll talk about knee pain, one of the more common injuries we see, especially as marathon season rolls around.  We have previously discussed Iliotibial Band Friction Syndrome (which creates pain on the outside of the knee), so today we’ll look at the inside of the knee and specifically the Pes Anserine (P.A.) Tendon.  

This tendon, which means ‘goose foot’ in Latin, is actually the connection of three hip muscles onto the inside of the knee:  the Sartorius, Gracilis, and Semi-Tendinosis (the inside hamstring.)  (In the photo above the tendon is where the blue and brown lines converge at the knee.)  Pain and inflammation of the P.A. Tendon is called Pes Anserine Tendinitis or Bursitis.

Pes Anserine pain is felt distinctly on the inside of the knee potentially during and after running, jumping, climbing stairs, and other activities.  The pain may or may not respond to ice and NSAID’s, does respond the rest, but can become quite severe if training continues.  This is one of those injuries that athletes may self-manage for long periods with stretching, foam rolling, icing, and reducing training but without ever getting it truly solved. 

Another structure nearby that can also create inside knee pain is the medial meniscus.  It’s important to differentiate the two as a medial meniscus tear won’t necessarily respond to conservative care and can require surgery.  Two symptoms that point to a P.A. injury are medial knee pain after prolonged sitting and also pain in the rear leg with a lunge type motion.  Meniscus pain is generally better with rest and would likely be worse in the front leg with a lunge.  An upper tibial stress fracture could also cause pain in this area.  An accurate diagnosis is essential as the treatments for these three injuries are very different.

Note:  As always when we write about injuries you’ll see references to the concept of ‘muscle inhibition’, where-by muscles become not just weak but overtly ‘turned-off’ and unable to fire.    This concept is often not fully appreciated and yet can be critical to really getting to the root cause of how injuries develop.  Inhibition usually stems from issues with the joint(s) that the affected muscle attaches to or near.

There is a great saying about knees, one that we believe: ‘The knee has the unfortunate circumstance of being located between the hip and the ankle.’  Outside of overt trauma, most repetitive knee injuries start with biomechanical issues in the hip joint above and/or the foot below.  The P.A. is no exception; pain here usually stems from problems in the hip or foot, causing the Sartorius and/or Gracilis to tighten as they try to over-compensate.  We have not seen many cases of P.A. directly attributable to the Semi-Tendinosis, despite the bad rap that tight hamstrings receive.  The common scenarios we do see leading to Pes pain are:
  • Imbalances between the hip flexors and the gluteus maximus causing compensation in the Sartorius.    Especially when the hip flexor is overtly inhibited, the Sartorius (being partially a hip flexor itself) will be forced to work excessively.
  • Weakness and especially inhibition of the adductor muscle group, causing the Gracilis to compensate.  This scenario may or may not have accompanying gluteus medius weakness.
  •  Foot weakness, especially if accompanied by a toed-out, over-pronating gait, causing the Gracilis (and adductors) to work too hard in helping to control the resulting extra lower leg motion.

In any of these scenarios the compensating muscle(s) become tight with time, causing the P.A. tendon and sometimes its under-lying bursae to become inflamed.

Treatment of P.A. Tendinitis involves not only releasing the tight, compensating Sartorius and/or Gracilis (or, if involved, the Semi-Tendinosis,) but also ascertaining why the muscle is tight in the first place (i.e. what is it compensating for?)  Active Release Technique works especially well in freeing up what is tight.  Typically much of this work is directed at the upper end of the muscles near the hip where the tightness usually first develops.  In fact trying to do too much work to the P.A. tendon itself at the lower end without first releasing the upper end can just irritate it further.

As with many injuries, releasing the tight muscles is fairly straight-forward, while figuring out the under-lying biomechanical cause is more complicated.  Some real-world examples we’ve seen include:
  • Several cases of former soccer players who subsequently took up running. The Sartorius is used more in soccer than most sports (think of trying to hit a hacky-sack with the inside of the foot and you get the idea of its action.)  However in each of these cases it wasn’t simply tightness to blame but also accompanying gluteal weakness.
  • A prior low back (pelvic) injury causing adductor inhibition and therefore Gracilis tightness.
  • A prior low back (lumbar spine) injury causing gluteus maximus and psoas inhibition and then subsequent Sartorius over-compensation.
  • An old groin pull (which usually occur in one of the upper adductor muscles,) in which the adhesions (scar tissue) present in the adductors bound up the Gracilis creating P.A. tension.
  • Old ankle injuries leaving athletes with residual weakness and a characteristic toed-out gait causing Gracilis compensation.
Full resolution of this injury requires taking into account these types of factors and helping the athlete rehab the under-lying imbalances.  Assuming there are no accompanying orthopedic factors like a meniscus tear, Pes Anerine issues are usually fully fixable.  Hence our moto: ‘If it ain’t broke, we can fix it!’