Stiff, but not Stiff, Stiff!

 We all feel stiff now and then. Many blame their ageing body, laziness, or strenuous activity for this. Many also blame muscles shortening, fascia thickening or scar tissue adhering. However, there are many misunderstandings and misconceptions around what is, and what is not stiff.

I think a lot of things can feel stiff, but not actually be 'stiff-stiff'. One of my favourite comedians Mickey Flannegan talks about going out but not 'out-out' watch it here it's brilliant. In this he describes how there are different levels of going out, there is 'popping out', 'going out', but then there is 'going out-out'. This I believe is the same for stiffness, there are things that are stiffish, stiff, but then there are things that are stiff-stiff.

Proper Stiff

Now I'm sure you're thinking 'what the hell is this idiot going on about' so let me explain some more. When I say something is stiff-stiff, I mean it's proper stiff. I mean it's stiff due to 'true' physiological changes of some structural change. There are two causes for things getting stiff-stiff, they are...

Joint Surface Changes

Soft Tissue Changes

Joint surface changes are often called arthritis or arthropathy and these processes can cause a joint to lose movement that may or may not be accompanied by pain. Despite common belief not all joint surface changes are painful. In fact, a lot are not painful, and the severity of joint changes are often poorly correlated with levels of pain or disability reported (ref, ref, ref, ref).

However, a loss of movement with or without pain combined with observed joint surface changes seen on imaging would be what I class as one cause of 'stiff-stiff'.

The other cause for things to become 'stiff-stiff' is soft tissue changes. All soft tissues are susceptible to adaptive shortening due to many reasons, but the most common soft tissue to shorten are muscles.

Our muscles shorten by losing contractile units called sarcomeres. This can occur through ageing (ref), disease (ref), lack of activity (ref), or even too much concentric exercise (ref, ref). Other non-contractile soft tissues such as tendon, ligament, fascia can also shorten due to pathology, injury, or immobility (ref, ref, ref).

Soft tissue changes are without a doubt the most common explanation given as to why we feel stiff. However, although soft tissue changes could be a cause of true stiffness, I believe most are not. That because, despite common belief, soft tissue changes just don't happen very easily or quickly and most of the time they do not explain why people feel stiff.

Stretching Mice

I often hear people blaming sedentary behaviour for causing stiffness due to changes in soft tissue, and there is no doubt that long periods of immobility can make us FEEL stiff. But does it actually cause true structural changes in our tissues.

For example, long periods of sitting are often blamed for shortening our hip flexors. Theoretically, this makes sense, long periods of sitting place our hip flexors in shortened positions which must cause adaptive changes in them, right?

Well actually it's just not that easy to shorten hip flexors muscles or any other muscle for that matter. To physically shorten a muscle through inactivity there has to be a substantial amount of immobility over a substantial amount of time, and I mean really substantial.

To cause true structural shortening of the hip flexors you would literally have to sit perfectly still, continuously for 23.5 hours a day, 7 days a week, probably for a month or three, not 8-12 hours a day 5 days a week like most do with occupational sitting.
The reason hip flexors, or any other muscle, just don't shorten with most long-duration sitting is that just a little bit of movement such as standing up, walking, or even lying down flat will reverse the effects of the muscle being in shortened positions for long durations. Movement doesn't actually have to be done that much, or that long to reverse the effects of immobilisation or sedentariness.

For example, it has been shown that just as little as 30 minutes of active movement is all that's needed to reverse the effects of complete immobility for 23.5 hours a day (ref). Yes I know this is a mouse study, but it demonstrates how hard it is for mammalian soft tissues to permanently shorten, and how even small amounts of movement can counteract large periods of immobility.

This is not to say muscle shortening doesn’t occur over longer time periods due to less activity, nor is it to say that movement or stretching can prevent contractures for forming especially if immobile due to neural or other health issues (ref). But it highlights that no soft tissue changes occur as quickly or as easily as most tend to think or claim.

Other Reasons

So if soft tissue changes don't occur as quickly or as often as we think, what else is causing so many people to feel stiff? Well, there are a number of other reasons for feeling stiff that are not as well known or recognised, and these are...

Fatigue and/or Deconditioning

Fear, Guarding, and/or Protection

These causes of stiffness are what I class as 'stiff' but NOT 'stiff-stiff'.

Stiffness due to deconditioning or over protection is not due to any structural changes to the joint or soft tissues. These causes of stiffness are due to central and peripheral neural mechanisms protecting and guarding the system for various different reasons.

It may be due to things such as an expectation of pain, or a fear of harm, or just wanting to take things easy and go slowly for a while. All these reasons can and do cause us to protect ourselves and give us the feelings of stiffness (ref).

For example, you know that feeling of stiffness you get after a long run or heavy gym session, that is your body trying to 'protect itself' from any further perceived 'harmful' activity until it has sufficiently recovered. It is of course also due to physiological adaptive processes as well (ref).

Protective non structural stiffness is not as well recognised or even considered as a potential cause of why we all feel stiff from time to time. Instead we blame shortened psoas muscles, tightened fascia, or dodgy joints. Protective non structural stiffness is also not recognised as an explanation as to why some 'stiff' things become less stiff really quickly, really easily sometimes!

Frozen but not Frozen

One of the most common things I see nearly every day as shoulder specialist is the enigma of a pathology called frozen shoulder. True pathological frozen shoulder, called capsulitis, causes significant soft tissue changes to the joint capsule causing it to thicken, shrink and contract (ref).

However, what is sometimes thought and diagnosed to be a true pathological frozen shoulder actually isn't. Instead, some true frozen shoulders are just overly protected, overly guarded painful shoulders with no true capsular tissue changes.

To make things really difficult these overly protected shoulders can present like and mimic true pathological frozen shoulder perfectly, having just as much pain, functional loss of both active and passive movement with normal looking x-rays.

What tends to give them away is sometimes these overly protected shoulders regain a lot of shoulder mobility in a short period of time after some treatments such as local anaesthetic or corticosteroid injections, manual therapy and even exercise.

A true pathological frozen shoulder joint capsule just doesn’t and can't change quickly with any treatment except surgical debridement. Therefore if some manual therapy, injection or exercise increases movement in a few days or weeks, or even minutes of treatment something else was preventing the movement, not the joint capsule.

This something else is often, fear, pain, guarding and protection.

Sudden changes in shoulder movement has been seen in frozen shoulder patients under general anaesthetic. This small study here found patients with suspected true pathological frozen shoulders actually had FULL range of movement when placed under general anaesthesia.

Again if there were true joint capsule changes the range of movement would still be reduced regardless if the patient was under general anaesthesia or not. So it appears these patients had what the authors called 'active stiffness' or what I like to call a 'Frozen Brain'.

Frozen Brains

Frozen Brains are also why I think some sketchy, dubious treatments appear to work on stiff things. Treatments such as hydro-distention, shock-wave, acupuncture, or any of the manual therapy techniques often claim to loosen capsules, release muscles, and break up adhesions and contractures when they suddenly improve movement. In fact what these treatments may have done is simply reduce fear, guarding and protective mechanisms around a painful area!

There is simply NO way any of these passive treatments can change soft tissues, especially pathological joint capsule tissue when you consider its resistance to mechanical deformation is well over 650kg/cm2 (ref), and the average force applied to a shoulder during manual therapy is just over 20kgs (ref)

This clearly demonstrates that the forces during ANY manual therapy are nowhere near close enough or done over long enough durations to change tissue structure. Therefore any improvements made in movement with these treatments I suspect are protective stiff shoulders masquerading as true frozen shoulders.

Summary

Many things can feel stiff, but a lot of what we feel stiff isn’t because of soft tissue or joint changes. Instead a lot of stiffness can be due to non structural mechanisms due to pain, protection, fear, or fatigue!

How much true physiological stiffness is there in painful backs, hips, knees, and shoulder, and how much is protective guarding due to patient's pain, fear, fatigue or threat is hard to say, but it should always be a consideration in most?

As always thanks for reading

Adam