Im 15 and ive had it for a few years. it is completely pain free now but the lumps are still there. has the tendon calcified at the insertion point? the lumps feel like bone (i have it in both knees 
). will osd affect sprinting or anything even though there is no more pain?
I also have/had osgood slaughters disease, in fact I was placed on crutches 5 times for it had 2 full leg casts and 2 air casts for it.
It ended both my basketball and baseball careers back going into highschool
I forget the main reason for the swelling, but it is not calcification of the tendon and is common in osgood slaughters.
With osgood slaughters, well at least for me I have to stay away from long term use of heavy impact exercises, I cannot practice at all for jumps, and usually use box jumps rather than regular jumps, just stay away from a lot of pounding, because once you start feeling it coming back its usually too late.
Back to the lumps, they usually stay for a long time if not indefinately. The bottom part of my knee cap is still sore to the touch 9 years later. However if your careful it wont really affect your performance.
i had it 11-12yrs ago when i was 18or19 for 12mnths. the lumps are still there, but the pain is completly gone and nothing i do affects it.
I had it when I was 13-15. I’m now 22 and still running track. The only pain I ever get in my knee is patella tendonitis. I’m not sure if this is related to the osgood-schlatters or not. I had the lumps for several years but only had pain when I was playing a lot of basketball and doing a lot of hurdling. Other than that I noticed the pain going away a long time ago.
the lumps are spurs of bone growth which are the result of the inflammation of the tibial tuberosity. because the patellar tendon is inflamed, the body adapts with the spur growths in an attempt to relieve the strain on the tendon. the tendon has not calcified, and if you manage it well you won’t have too many problems with it in the next few years. until you are 16 the bones haven’t fully matured and so you are still at risk of it being aggravated.
i’m 16 now and haven’t had any problems with it this year after having it really bad when i was 15 (although not to the point of having it immobilised). you’ll be fine as long as you maintain a good level of flexibility in your quads and hammys (especially), ice it after doing any activity that puts excessive pressure on the knees, and avoid anything that may be particularly damaging (e.g. plyos or weights). it shouldn’t affect your sprinting, i’ve had my best season ever coming off the back of being injured last year, and i’ve also been able to tolerate some low level plyos - but haven’t done any weights as yet. remember, if you feel pain, stop, because pushing through it will only set you back even further. good luck to you