Final answer:
To diagnose a herniated disc, a physical examination is conducted followed by an MRI if needed, since it provides clear images without radiation. Pain in a lower limb after lifting a heavy object can occur if the action leads to herniation of a disc, compressing a spinal nerve and causing sciatica.
Step-by-step explanation:
To diagnose a herniated disc, a physician will typically start with a physical examination and review of medical history. If the examination suggests a herniated disc, imaging tests such as Magnetic Resonance Imaging (MRI) may be ordered to confirm the diagnosis. MRI is widely considered the best diagnostic tool for herniated discs because it provides high-resolution images of the spine, allowing doctors to see the soft tissue of the discs and spinal cord without the use of radiation. A herniated disc occurs when the nucleus pulposus, the gel-like center of an intervertebral disc, protrudes through a weakened anulus fibrosus. This can result in compression of a spinal nerve, causing pain and/or muscle weakness in areas served by the nerve. Lifting a heavy object can produce pain in a lower limb if this action causes a weakened disc to herniate. For example, bending forward to lift a heavy object can place excessive pressure on the posterior part of a disc if there is existing weakness in the anulus fibrosus. This pressure may cause the nucleus pulposus to push through the outer ring and compress a spinal nerve, often leading to sciatic pain which radiates from the lower back down into the leg.