I had a question recently, about manual therapy in the foot and why I often use an indirect technique.
"It seems that in this case and others, even on yours and Rods online videos, that indirect techniques seem to be used for navicular? Does your experience show that it responds best to that?"
The key to accurate palpation of joint movement is first to identify barriers.
So let's look at a scenario. You're doing a local biomechanical evaluation of talonavicular arthrokinematics, or joint play. In larger joints like the hip, the above image allows for the assessment to reveal a large range of motion between first and second point of resistance. This larger range between R1 and R2 is often related to a "springy" feel, due to the elasticity of muscular and fascial tissue. In a smaller joint like the talo-navicular joint, however, there's no muscle or fascia limiting the range of movement - it's only ligament - so the joint play, the give, the movement, is going to be small, but there should be some movement. Think of a range of movement at the TN joint in both directions of one plane. Eg navicular pronation and supination. There is a resting position of the joint, with a central zone where there’s "a little give" either way before you meet resistance.
Let's say you move it one way from the central zone eg into supination, and you meet R1 straight away. And you release your fingers and “let it settle” back to the neutral zone. Then you move it into pronation and notice that there’s a little more give before R1 compared to supination. You decide they could do with more supination. The usual physiotherapy technique would be direct - that is to say, the technique would be to mobilise the bone in the direction of supination. For example, Maitland style grade 3-4 for stiffness, or grade 5 manipulation, also known as HVLA (high velocity low amplitude) or CMT (chiropractic manipulative therapy). Except the supination R1 came on immediately from neutral zone and R2 is probably at the same place as R1. And…. I'll bet that your Physio manual therapy education wouldn’t have taught you to feel for “give” and to note R1 and R2, and if it did, you wouldn’t have refined it for small joints like the talo-navicular joint, so you have no feel for supination give and all you know is grade 3-5 for stiffness, direct.
Now think about this. What if the navicular was already “hard up against the end range of supination”? I mean, what if R1 and R2 were met immediately that you moved the navicular into supination?
I have to ask you, "Will directly mobilising further against the hard end-feel, the hard barrier, create more give or will it create potential joint instability? (I don't believe it will create joint instability in this joint, it's so well packed and supported.) Or will the bony and ligamentous integrity be so strong that you simply don’t make any difference? So, what if you bring the navicular indirectly from the restricted direction, ie towards pronation, and then, in that “eased” position, you have created an opportunity for the nervous system to get to know this eased position, or to interpret the eased position as a position that feels easier? You can "make the nervous system aware of it" via cueing relaxed breathing while the navicular is eased, to "remember a motor control of that movement".
And then, here's the modification from typical osteopathic technique - in that eased position, the next thing you do with your manual therapy is that you involve the nervous system by having them do an active movement of the physiological movement they couldn’t do before, for about 5 reps. For example, if the person had lost some dorsiflexion mobility, you would ask them to do dorsiflexion towards as much as they could do.
In some ways it has similarities to a Mulligans MWT - a Mobilisation With (active) Movement. If the person does an active isometric contraction in the direction opposite the dysfunctional physiological direction, it’s an MET, and if they do it a concentric contraction in the directions originally described then it has reciprocal inhibition about it - useful if the limiting tissue is Myofascial.
Then, you re-check the supination accessory movement, or joint play, which will be a passive test. And then you check the physiological movement that was limited, in this case dorsiflexion, tested passively, first, and then active.
Did you change the accessory mobility dysfunction of supination, as per the local biomechanical examination?
Did that change of accessory mobility dysfunction change the passive physiological mobility dysfunction of the breakout that took you there?
Does the improved breakout change any top tier movements?
It often does.
That explains why I like indirect technique.