Dear Concerned., Thanks for writing to us. As you have not mentioned any pain during standing//movement of ankle joints//movement of toes etc ,clinically fractures are ruled out. You would have vilolently shaken ur affected leg during your Karate Practice/ or Injured a part of the Soft Tissues in your leg including blood vessels .As a result of trauma to veins in the legs the ruptured vein would have got temporarily closed by a blood clot which gets dislodged by movement.The blood extravasates (when clot dislodges)into inter muscular space which is enclosed by fascial sheaths ,hence space constraint the tightness and heavyness. The swelling if it is constant ,it may indicate muscle contusion as well. The above can be proved by the under mentioned investigations., A)Plain X-Ray of the involved part AP and lateral views. B)Arterio venous doppler Studies.(C)Ultrasound Study of injured area. Kindly consult an Ortho-Surgeon // Sports Medicine Consultant for further management. Wishing you a Speedy recovery., Best Regards., Dr Lt Cdr ASN Bhushan.