What kind of doctor should i see if i have muscle weakness in my quadriceps.

Several: Several specialties can evaluate including Neurology, Orthopedic Surgery, Rheumatology and Physical Medicine.

It's hard to say: As the type of doctor you may be best served by depends on the cause of your weakness. For instances like this without more history or the ability to examine you, I would encourage you to start with your primary care doctor. If it's related to primary muscle weakness you may need to see a neurologist or rheumatologist. If it is related to a bony or spine problem you may need to see an orthopod.

Sports medicine: Typically we need more history. Was there prior trauma, radicalization or knee arthritis or surgery that caused the weakness ? There are other less common possibilities as well. A sports medicine doc or Orthopedist can help with diagnosis and treatment.