I mangled the meniscus in my knee while trail running. Stanford said repairing it would be a 50-50 proposition. (Maybe it would improve, maybe not.) But, ongoing strength training was 100% going to help. Based on a friend's recommendation, I started working out with Gretchen Graves. When I work out with her, I can cycle and run up and down stairs. When I miss more than a session or two, my knee starts hurting 'til I'm pathetic and limping.
Gretchen is insanely detail-oriented. Every workout is tracked and recorded. I never have to wonder how many reps or pounds are appropriate for a given activity — it's all right there in her spreadsheet. She mixes things up a LOT, so I'm always wondering what she's going to throw at me next. Her workouts are HARD, but they don't leave me incapacitated for days afterward. (We've all had trainers like that, right?) And, she's incredibly diligent at working the underperforming muscle groups that led to my injury in the first place.
Worth every penny.