Assessing stiffness: muscle, soft tissue or joint capsule?

“Why is my dog stiff?” sounds like it should have a simple answer. It does not. Stiffness can come from muscle, from soft tissue, or from the joint capsule, so assessing stiffness well comes down to telling one from another.

Assessing stiffness: start with joint play

Confronted with an area of decreased motion, I go to motion palpation and joint glides first. Feel for joint play. Where is the stiffness, and is there any? Muscles and tendons do not provide resistance in this motion. Think of an arthritic hip: it will feel stiff long before it reaches end range, because the joint capsule has tightened.

Think about what you are stretching

While you are moving through range, consider which muscles you are stretching at the same time. Shoulder flexion also stretches the supraspinatus and biceps tendons. Start a biceps tendon stretch with the elbow in extension before adding shoulder flexion and the focus stays on the biceps tendon, without involving the supraspinatus or the glenohumeral joint. Equally, you can move into full glenohumeral extension without putting teres major, latissimus dorsi, deep pectorals or triceps on stretch, if you block scapulothoracic motion.

Both sides, and both directions

Always check agonists and antagonists, and always check left and right, so you get a feel for what is normal or abnormal for this patient. How does this joint compare? Some patients are hypermobile everywhere and others are stiff everywhere. That has to be factored in.

If you suspect a muscle or tendon is involved, or the restricted or painful motion could indicate either a joint or a soft tissue structure, palpate the muscle, tendon and ligament directly to see whether it is painful.

Active against passive

How does active range of motion compare to passive? This is obviously easier in a person than a dog, but there are tests that get at AROM. Can the dog sit and lie down square? Both require full hip, stifle and tarsus flexion. The canine shoulder does not lend itself to much AROM testing.

Remember that AROM invites compensation. A dog with hip dysplasia compensates with stifle or tarsal hyperextension at the end of stance phase, circumducts or externally rotates the hip, and shows a hip and pelvic drop at the walk. A patient can learn to actively avoid end range by letting other joints move more, varying rotational positioning, or asking certain structures to stretch or work harder to complete the task. A reduction in PROM is therefore more likely to be a joint issue.

End feel

Then we arrive at my favorite place to be: end feel.

End feel is one of the key factors in deciding whether the problem is capsular, ligament or capsule; soft tissue apposition, where muscle or fat impedes further motion; springy, as with a meniscal tear; spasm, indicating acute injury; elastic tendon stretching, often hypermobility; bony, such as elbow extension; empty, which is never good; or facilitation, test stifle extension in a chronic partial CCL tear case and you will feel resistance to even going into extension.

End feel tells you what you are dealing with as far as joint function is concerned.

Keeping all of this in mind, we can arrive at a working clinical picture to guide treatment, or the need for referral for a surgical consult or further diagnostics.

When to refer

Some findings mean the picture needs more than a hands-on assessment. An empty end feel, pain out of proportion to what you are finding, a facilitation pattern that points to a partial cruciate tear, or any neurological deficit are all reasons to stop and get further diagnostics or a surgical opinion before going further with treatment.

If you have a stiff patient you would like a second pair of hands on, you can send them to us through the vet referral form. We work alongside the referring veterinarian and report back on what we find.

Related reading: Myofascial techniques in veterinary rehabilitation: a review · The place of myofascial treatment in canine chronic pain

Questions colleagues ask

How do you tell capsular stiffness from muscle tightness?

Start with joint glides. A tight capsule resists joint play and is felt before end range, while muscles and tendons do not resist glides. If the restriction changes when you reposition the joint above or below, so a two-joint muscle is on or off stretch, think muscle or tendon rather than capsule.

Why compare active and passive range of motion?

Because dogs compensate. A dog can avoid end range actively by letting other joints move more, so a reduced active range on its own tells you little. A reduced passive range is more likely to be the joint itself.

What does an empty end feel tell you?

That something is stopping the movement before any tissue does, usually pain or guarding. It is not a finding to treat through. It is a reason to look further.