It would be nice if a doctor could stop and explain everything he is doing and examining while he was in the process of doing the examination. Unfortunately in this day and age when a doctor may be seeing dozens of patients a day he may not have time, or take the time, to do so.
We’re lawyers, not physicians or doctors, but after having read thousands of pages of medical records here’s an educated guess as to what the doctor is doing. Damage to the sciatic nerve, the main nerve exiting the spinal column in the low back and going down the legs, will often result in certain abnormalities which a doctor can spot while doing a physical examination. These include weakness when bending the knee, loss of the ability to rotate your foot up or down (thus walking on your toes or heels), loss of reflexes to the knee and ankle, difficulty bending forward or backward at the waist, and pain when lifting your straightened leg up off the exam table.
In this situation what the doctor is looking for is objective evidence to confirm or supplement your subjective reports of an injury and subsequent pain.