The treatment for Osgood-Schlatter's Disease is mostly relative rest. This does not mean that you have to eliminate all activities, but it does mean that you have to be more choosey. When Osgood-Schlatter's Disease presents itself it usually lasts for 1-2 years and then goes away on its own. But during that time period ‘stop-start’ sports are going to be more aggravating because they create the most tension on the affected structures (patellar tendon and tibial tuberosity). These include sports like football, basketball, soccer, volleyball, and tennis, but other activities like jumping on a trampoline can also increase pain and swelling. So you may have to limit your game or practice time and even eliminate non-sports activities that worsen symptoms. Limiting the number of sports that you play in a year to one or two is a good strategy.
Other helpful measures are anti-inflammatory medications (Ibuprofen), ice after activity, increasing thigh muscle flexibility and strength, and a supportive band (patellar strap) that goes across the knee.