Physical Therapy: Burning pain

I have a headache and can't sleep. Thought I would write a little about what I learned today in PT.

An older patient came into the clinic claiming she experienced a burning sensation in her knee when climbing the stairs. Burning sensations generally fall into three categories: Lactic acid buildup (technically not an acid but that's another story),  bone on bone grinding, or nerve pain.

When diagnosing, you never rule in diagnoses, you can only rule out. So you work through what a problem isn't instead of what it is.

It was not lactic acid build up because the pain is too centralized. Generally lactic acid build up creates a burning sensation in the muscle. Since the burning pain occurred only at the knee joint, we can rule out this diagnosis.

It was not nerve pain because again the pain was too centralized. Nerve pain can take any form of sensation but generally if it's a burning sensation it would be a form of radicular nerve pain, which means it the pain radiates from the spinal cord all along the nerve pathway. So the pain would go all along the leg, which was not the case with the patient today. Now the pain could also be a referred pain, where the pain is experienced at one location but originates from another. However, because the ankle and hip joints of the patient would relatively stable, we could rule this diagnosis out as well. Referred pain generally appears most commonly in the glenohumoral (shoulder) joint and deltoid tuberosity of the arm.

We concluded that the burning pain was likely caused by joint on joint grinding, essentially hypercompression of the quadriceps on the patella. As the patient climbs up the stairs, because she has decreased motion in her right leg, she can't fully extend that leg out when climbing the stairs, so as she steps to push her self up onto the next step the quadriceps are compensating for the lack of motion and thus compressing the joint more so than natural.