Hello, I understand your concern. Sudden severe pain in the right lower leg may arise due to:

a)Muscle strain or fatigue – where it can be relieved by rest and cold or warm compression or there may be a tear of the muscle.

b)Exercise related injuries- In your brother s case, it is not possible as he has got an enlarged heart and other heart problems.

c)Tendonitis – usually seen in sports events.

d)Venous insufficiency like deep vein thrombosis

e)Peripheral arterial disease seen in cold and pale limbs and increased sensitivity to pain.

f)Medical conditions like rheumatoid arthritis, thyroid disease or multiple sclerosis causes leg pain or cramps.

g)Compression of sciatic nerve sciatica which induces herniated spinal disc

h)Spinal stenosis or irritation from a tight muscle ( pyriformis) leads to piriformis syndrome , this pain starts at the buttock , felt on the side and back of the leg all the way down to the foot .

i)Broken bone may be a fracture or a sprain.

j)Peripheral neuropathy.

I would suggest you get a complete physical evaluation and blood tests, venous Doppler of right lower leg, x ray right foot and consult your doctor with these reports. Thank you.