Why do marathon runners develop knee pain and what can you do to start addressing the issue?
Knee pain—often referred to as runner’s knee—is one of the most common injuries seen in marathon runners across all ages. Whether you’re training along the beach paths, local trails, or neighborhood roads, knee pain can quickly derail your training plan.
While many runners assume knee pain means something is “wrong” with their knees, the issue is rarely the knee itself. In most cases, runner’s knee develops when training demands exceed the body’s ability to handle load.
What Happens to Your Knee During a Run
Running is essentially a series of single-leg hops. At no point are both feet on the ground at the same time. That means each individual leg must absorb and control your full body weight with every step.
During a run:
Each leg absorbs up to 2–3 times your body weight
This force is repeated thousands of times per run
The load must be tolerated for prolonged periods, especially during long runs and marathon races
For example, a 160-pound runner may place nearly 480 pounds of force through one leg with every stride. If the muscles responsible for absorbing this force fatigue or lack strength, that load is transferred directly to the knee—often resulting in runner’s knee.
The Knee Is a Load Transfer Joint
The knee acts as a load transfer point between the hip and ankle. It depends on surrounding muscles—not passive joint structures—to absorb impact and control movement.
Key muscles that protect the knee include:
Quadriceps – Control knee bending and absorb impact
Hamstrings – Support knee stability and decelerate the leg
Glutes – Control hip motion and limit excessive knee stress
Calves – Absorb ground reaction forces and reduce load traveling upward
When these muscles are undertrained, the knee is forced to compensate.
Why Marathon Runners Develop Runner’s Knee
Many marathon runners focus heavily on mileage but skip strength training. While running improves cardiovascular endurance, it does not sufficiently build the muscular strength and tissue capacity required to tolerate repeated high loads.
Problems arise when:
Weekly mileage increases
Long runs get longer
Speed or hill work is added
…but muscular strength and endurance remain unchanged. This mismatch leads to cumulative overload at the knee, often presenting as runner’s knee midway through a training cycle.
Building Capacity to Prevent Runner’s Knee
Preventing runner’s knee isn’t about running less—it’s about building a body that can tolerate marathon training.
An effective approach includes:
Progressive strength training for quads, hamstrings, glutes, and calves
Single-leg exercises that reflect the demands of running
Gradual mileage progression that allows tissues to adapt
When strength and capacity improve alongside mileage, knee pain becomes far less likely.
How Physical Therapy Help Marathon Runners?
Working with a physical therapist allows runners to address knee pain at its source. Physical therapy focuses on improving strength, control, and endurance in the muscles that support the knee—not just treating symptoms.
Physical therapy for runner’s knee may include:
Targeted strengthening of the lower body
Load management and training guidance
Gait and stride analysis to identify mechanical contributors
Small stride adjustments—such as addressing overstriding, cadence, or hip control—can significantly reduce knee stress, especially when each leg is managing forces of up to three times bodyweight for extended periods.
By combining strength training, gait optimization, and individualized care, physical therapy helps runners return to training with confidence.
Schedule a Free Discovery Call
If you’re dealing with runner’s knee or knee pain during marathon training, you don’t have to push through it alone.
Schedule a free discovery call to talk about your symptoms, training goals, and whether we at Weak End Physical Therapy is right for you.
👉 Book your free discovery call here: https://weakendpt.janeapp.com