A good friend of mine asked me about his recent right knee pain. He is an active guy who is currently complaining of pain in his anterior right knee. On exam he has patellar tendinitis findings. Easy enough, treat the patellar tendon with eccentric exercises and all set.
Not so fast. Listening a bit more it turns out he has chronic swelling in his right ankle, although no pain. It appears he sprained his right ankle 20 years ago and this injury, while not painful, has never fully healed. The presence of chronic swelling in his right ankle represents likely ligaments that were stretched out during his previous injury that have never fully healed. This chronic subtle instability in the right ankle can lead to mild restriction in ankle range of motion, which in turn prevents the ankle from fully flexing and dorsiflexing during ambulation and running. This in turn results in more pressure placed on the knee, and likely exacerbates his patellar tendinitis.
So what is the right way to treat this? Certainly treat the right patellar tendinitis with appropriate exercises. In addition strengthen the hips to offload pressure on the knee. But he will also need to work on strengthening and stability exercises for the right ankle long term. If this combination of treatments does not work, then platelet rich plasma to tighten the ligaments surrounding the ankle and to heal the tendon damage in the patellar tendon.