hi, thank you for providing the brief history of your husband A thorough clinical orthopedic assessment is advised. As mentioned by you that your husband lifted the heavy dog and had a muscle sprain, which later now giving him pain down the left leg. This is a classical symptom of the degenerative disc disease. Like, what happens is, initially due to sudden jerky bending movements and carrying heavy weights, the disc takes the pressure for which the muscles support and gets strain, on later stages due to ageing of the spine , which is a common and normal physiological process, the disc in between the two vertebral bodies gets damages, which later pinches the nerve root and give electric shock pain travelling from back to down the leg. An MRI is performed to check the soft tissue injury status and based on it treatment is planned. Usually with simple medication and physical therapy patient recovers in 2-3 weeks of time. Exercises are taught and advised to perform later in home, as to avoid future recurrences. in my clinical experience i see every day back ache cases with radiating pain from back to the leg, they respond well to a combination of medicine and physical therapy. Since physical therapy is non invasive , it has benefits and you can even find the research articles on the net how effective is physical therapy for the symptoms of your husband. Regards Jay Indravadan Patel