As a clinical practitioner, when a client presents to you revealing the story of their bodily mishap, the inquirer will weigh all available evidence to come up with a satisfactory answer. The textbook of a career is littered with observations, hunches and discoveries. All you have learned is in there, but it has also built into it healthy suspicion, intuition and a rogues' gallery of bizarre memorable maladies that will be seen once in a lifetime.
Diagnosis is the Sherlock Holmes of clinical experience. It is the sleuth inside let out on one more mystery to solve. You have your Doctor Watson to smooth off the sharp edges of your grandiose ideas, and your Doctors Foreman, Wilson and Chase to bounce rejectable notions at your Gregory House.

Yes, I may have just talked up the everyday task of each clinician in physical medicine, but you don't just come to us for symptom relief. It is all very well to offer treatment, but treatment without justification is just recipe "care". We need to ask ourselves questions about "what else could this be?" This is called differential diagnosis and it pokes and prods at the approach that treats first and asks questions later.

Let us consider the differential diagnosis for something we all will likely experience: knee pain.

Strain - a muscle is injured. Over stretch of muscle tissue tears fibres and causes pain, bruising and limping. This is very common.
Ligament sprain - again a common traumatic cause of knee pain that the patient will clearly recall. The knee joint will have been forced or twisted outside of its natural hinge and rotation directions.
Housemaids knee or bursitis - blunt trauma or long periods spent on the knees point the suspicious inquisitor to this tissue.
The nerves - not a major contributor to knee pain, but sciatic, femoral, tibial and peroneal nerves are some that may make a person think they have a knee problem when they may have a problem elsewhere.
Osteoarthritis - the consequences of time's onslaught. It has characteristic signs of value to the sleuth.
Meniscii - the jelly-like pads that cushion the knee, these can be torn twisting with weight bearing, or in my own experience giving horsey rides to two under-fives at once. As with the other possibilities for diagnosis, these tissues have characteristic problems with pain around the joint line and loss of kneeling ability often unique to their being damaged.


The less frequent problems are detained for questioning, but usually have no part to play in the bulk of "crimes". Infection, malignancy or cancer, rheumatoid arthritis or auto immune disorders are the suspects you should rule out as a habit. Saying this, there is an adage that cautions the clinician not to see the bizarre in the everyday. "When you hear hoofbeats, think horses, not zebras." You won't see much of Charlie the Unicorn either. If you didn't have this in mind, you might see Disseminated Synovial Chromatosis, Fabella Syndrome and Melorheostosis as regular knee troublers - they are not. So a trained diagnoser or diagnostician is looking at all the clues in your story to form a plausible answer.

It is never as simple as something like "your back is out". So if you want to get your back diagnosed, you really need to go through the carefully selected appropriate tests to rule in or out what's really going on.

There are other tests that are called on when conventional manual tests or observations do not clearly show the true cause of your problem:

X-ray: usually done in the early stages of injury by the medical team at the accident and emergency clinic. They show up fractures and degeneration. Very occasionally a fracture will show up later. The scaphoid in the wrist often hides a fracture until nearly two weeks have passed. Sometimes a fracture is missed because the signs and events leading to injury didn't warrant suspicion of a fracture, but clinicians have several robust rules to test and consider, which will lead to the appropriate test being done.

Ultrasound scans: useful to image tendons and in detecting tearing or bleeding into muscle. These are becoming increasingly popular with physiotherapists to watch the action of a muscle throughout its full range. We are now able to detect subtle weaknesses or delays in the switching on of muscle, which can lead to a very specific diagnosis. The availability of this is still fairly limited, but it is hoped that this technology will become commonplace in most physiotherapy practices.

MRI: Magnetic Resonance Imaging is a sophisticated look at the soft tissues in a way similar to slicing the affected part of the body many times and looking at each slice. I have had the pleasure of being scanned four times now, and thanks to the kind staff at Wanganui MRI suite, I have been able to lie in a small, coffin-like tube for 30 minutes or so listening to what seem like heavy metal songs, one second long, repeated every half second. Thanks for the earmuffs. MRI is usually a request from a specialist, so to get here you will probably have sustained damage not amenable to treatment.

Blood tests: your GP will ask for these if there are unusual signs which might indicate immune dysfunction, infection or inflammation. This pathway will come later if you have just sustained an injury.

Diagnosis is the key to the doorway that leads to recovery. As we strive to find the key for you we are reminded to balance looking for the fewest possible causes that explain the problem (Occams Razor) with the idea that the patient can have "as many illnesses as he damn well pleases" (Hickam's Dictum) - statistics may say one simple problem is most likely but sometimes multiple causes can exist in a person, just to make it interesting for the sleuth, but then isn't that what made House such an interesting programme, and he saw a rare and implausible case once a week!

When you come seeking refreshment from what ails your human body, see diagnosis as part of that treatment too, because without a clinically reasoned foundation, we cannot build the bridge across to the other side of recovery.

Greg Bell is a physiotherapist practising at Bell Physiotherapy.