Knee pain is one of the most common complaints we see in runners — and two conditions get confused more than any others: runner's knee (patellofemoral pain syndrome) and patellar tendinopathy (jumper's knee). They can feel similar, they both dislike stairs and squats, and they both can show up after a spike in training. But they're different injuries, with different causes and different rehab plans. Getting the diagnosis right matters, because the wrong exercise program can make either one worse.
What Is Runner's Knee?
Runner's knee, or patellofemoral pain syndrome (PFPS), is pain around or behind the kneecap. It's usually linked to stress or overload at the kneecap as the knee bends and straightens under load. When the muscles supporting that movement, particularly the quad and gluteal muscles, aren't managing load well, the kneecap can experience more force and result in pain and inflammation.
Common signs:
Dull, aching pain around or behind the kneecap
Worse with stairs (especially going down), squatting, or sitting for long periods with the knee bent
Pain that builds gradually rather than starting from a single incident
Often affects both knees, or alternates sides
What Is Patellar Tendinopathy?
Patellar tendinopathy is an overload injury to the tendon that connects your kneecap to your shin bone (the patellar tendon). It's common in sports with a lot of jumping, sprinting, or sudden changes in load, which is why it's often called "jumper's knee" — but it shows up in runners too, particularly during hard hill sessions, plyometrics, or fast increases in training intensity.
Common signs:
Sharp, localised pain at the bottom of the kneecap, right where the tendon attaches
Pain that's often worse at the start of activity, eases as you warm up, then returns afterward
Tender to press directly on the tendon
Tends to affect one knee rather than both
Key Differences at a Glance
Runner's Knee (PFPS)
Pain location - around or behind kneecap
Pain pattern - Gradual, aching
Warm-up effect - Doesn't typically ease with warm-up
Common triggers - Stairs, squatting, prolonged sitting
Usually affects - Often both knees
Patellar Tendinopathy
Pain location - Directly at the tendon, below kneecap
Pain pattern - Sharp, localised
Warm-up effect - Often eases with warm-up, returns after
Common triggers - Jumping, sprinting, hill work, plyometrics
Usually affects - Usually one knee
Why the Diagnosis Matters
These two conditions respond to different loading strategies. Tendons like the patellar tendon generally respond well to appropriate, progressive, heavier strength work — they need tolerable load to adapt and heal. Patellofemoral pain, on the other hand, usually responds better to addressing the movement pattern first, often quad, hip and glute strength, before loading the knee more aggressively.
Treat patellar tendinopathy like runner's knee, and you risk under-loading a tendon that needs strength work to recover. Treat runner's knee like a tendon injury, and you might load a movement pattern that was the actual problem in the first place. This is exactly why an accurate assessment, not just a Google search, makes the biggest difference in how quickly you get back to running and the things you love.
What to Do Next
If you're dealing with persistent knee pain, the most useful first step isn't guessing which one you have, it's getting it properly assessed and diagnosed. A physio can identify exactly which structure is involved, how much load it can currently tolerate, and build a program that gets you back to running without the guesswork.
Knee pain doesn't have to mean stopping running altogether. In most cases, it means adjusting how you're loading it and that starts with knowing exactly what you're dealing with.
Kye Simpson, Senior Physiotherapist at Streamline Physiotherapy, Thirroul.