If you have stiffness in your knee especially with downhill or downstairs activity.
If you have pain when stretching your quads.
If you have swelling and or crunching with knee movement.
If you have tenderness when pressing on the patellar tendon below the knee cap.
Then you may have patellar tendonitis.
If those don’t apply, you may have something else going on. In which case I would see a PT or Physician for an accurate diagnosis.
Realize that patellar tendonitis is an overuse syndrome. So you must have been doing too much too soon and/or too much jumping. So you need to rest until symptoms subside. Otherwise things will only get worse. If you absolutely must be training still, keep it light. You can consider purchasing a Chopats brace which straps around the upper tibia/fibula to provide stability.
Try this treatment at home:
- Light stationary bike warm-up 5-10 minutes
- Hamstring stretch 3×30” (standing, sitting, or lying down)
- Quad stretch 3×30” (standing or lying down)
- Glute stretch 3×30” (sitting or lying down)
- Calf stretch 3×30” (standing)
- Foam Roller myofascial release of all leg muscles (see my Foam Rolling 101 post here)
- Decline single leg squat for 3 sets of 15 (squat down for 4 counts, then back up for 1 count)
- Leg Extensions machine for Quad strengthening for 3 sets of 15 (extend for 4 counts, then back down for 1 count)
- Finish with ice after any and all exercise (I recommend rubbing an ice cube on the tendon 3-5 minutes)
If this does not help, please see your Physician or a Physical Therapist.