Runner’s knee, also known as patellofemoral pain syndrome (PFPS) or anterior knee pain syndrome, is a common overuse injury that causes pain around or behind the patella. It often results from abnormal patellar tracking within the femoral groove, leading to irritation of the surrounding structures. This condition is frequently seen in runners, cyclists, and athletes who engage in repetitive knee flexion and extension.
As the name suggests, running is the most common cause of runner’s knee, but it is also quite common in non-athletes. Almost 25% of the world’s population have some form of knee pain, more specifically pain in the area of the kneecap.
The anatomy of the patellofemoral joint
The patellofemoral joint is where your patella articulates with the femur, or thigh bone. It plays a crucial role in knee extension by enhancing the mechanical advantage of the quadriceps muscle, acting as a pulley to improve the transfer of force. You’ll find the patella, or kneecap, at the front of your knee joint. It’s a small, triangular bone that is embedded within the quadriceps tendon.
Key anatomical structures around the patella include:
– Quadriceps Tendon: Connects the quadriceps muscles to the patella.
– Patellar Ligament (Tendon): Extends from the patella to the tibial tuberosity on your shin bone, helping in knee extension.
– Articular Cartilage: Covers the underside of the patella, allowing smooth movement over the femur, or thigh bone.
– Retinacula (Medial & Lateral): Fibrous structures, similar to ligaments, that help stabilize your patella.
– Synovial Bursa: Reduces friction between the patella and surrounding structures.
What should happen in and around my knee when I move?
Patellar tracking: The patella moves within the trochlear groove of the femur during knee flexion and extension, guided by muscle forces and ligamentous restraints.
Load distribution: Joint reaction forces increase with knee flexion, with the highest stress occurring around 60-90° of flexion due to quadriceps contraction.
Active stabilizers: Quadriceps muscle, especially the vastus medialis oblique (VMO), helps maintain patellar alignment.
Passive stabilizers: Medial and lateral retinacula, patellofemoral ligaments, and the trochlear groove shape influence patellar stability.
Contact Area: As flexion increases, more of the patella engages with the femur, reducing stress per unit area.
Now I have runner’s knee. What went wrong?
Runner’s knee is caused by abnormal tracking of the patella (kneecap) over the femur, leading to increased stress and irritation of the patellofemoral joint. There are a number of possible causes including:
1. Biomechanical Dysfunction
Muscle Imbalances: Weak quadriceps, hip abductors, or glutes fail to stabilize the kneecap. The strain put on the patella causes a compression in the femoral Groove. The higher the load on the quadriceps the greater the compression on the patella. The excessive pull on the quadriceps tendon on the top part of the patella can start tearing the tendon fibers. If the quadriceps muscles are weak it could cause a sideways pull on the patella that can cause the patella to run towards the in or outside that may run down the cartilage much faster.
Tight Structures: The iliotibial (IT) band, hamstrings, or lateral retinaculum pull the patella out of alignment.
2. Increased Patellofemoral Joint Stress
The downwards compression of the back part of the patella onto the femur will over time erode the cartridge and reduces its shock-absorbing function. This compression force is exacerbated when the quadricep muscle is shortened. Abnormal patellar movement leads to excessive friction and pressure on the underlying cartilage.
This causes microtrauma, inflammation, and pain, especially with repetitive knee flexion (e.g., running, squatting).
3. Cartilage & Soft Tissue Irritation
Chondromalacia Patella: Chronic stress may lead to softening or breakdown of cartilage under the kneecap.
Synovial Inflammation: Overuse can cause swelling of the synovial lining, further increasing pain.
4. Pain Mechanisms
Nerve Sensitization: Chronic irritation leads to increased pain signaling from the knee joint.
Causes of runner’s knee
Overuse and Repetitive Stress
Repeated bending and straightening of the knee (such as during running, jumping, or cycling) can lead to irritation of the patellar cartilage.
Excessive training without proper recovery increases the risk.
Muscle Imbalances and Weakness
Weak quadriceps, hamstrings, hip muscles, or glutes can cause poor knee tracking, leading to misalignment and pain.
Muscle imbalances result in improper force distribution across the knee joint.
Poor Running Form or Biomechanics
Running with improper form, such as overstriding or excessive inward knee movement (valgus collapse), puts extra stress on the knee.
Misalignment of the hips, knees, or feet can contribute to uneven pressure on the patella.
Foot Problems and Improper Footwear
Flat feet (overpronation) or high arches can alter the way force is distributed in the knee joint.
Worn-out or unsupportive shoes can increase impact and strain on the knee.
Tight Muscles and Limited Flexibility
Tight hamstrings, quadriceps, or iliotibial (IT) band can pull the kneecap out of alignment, causing friction and pain.
Previous Knee Injuries
A history of knee injuries, such as ligament strains, meniscus tears, or patellar dislocations, increases susceptibility to runner’s knee.
Hard or Uneven Running Surfaces
Running on hard surfaces (like concrete) or uneven terrain increases joint impact and may worsen knee pain.
Sudden Increases in Training Intensity
Rapidly increasing mileage, speed, or intensity without gradual adaptation can overload the knee joint.
Excess Body Weight
Carrying extra weight increases the force on the knee joint with each step, potentially leading to pain and irritation.
Runner’s knee affects 25-30% of runners.
I have runner’s knee – how bad is it?
At first you will have a dull, aching pain around or behind your kneecap, typically triggered by activities like running, squatting, or climbing stairs. Pain comes and goes, usually relieved by rest, and you will have some stiffness or discomfort around your knee after prolonged sitting. For now, your knee joint doesn’t feel unstable, and pain doesn’t affect your day to day activities, but you may notice occasional cracking or popping of your knee.
As the problem gets worse, pain becomes more persistent and occurs even during low-impact activities like walking or going down stairs. Now you may notice swelling and inflammation around your patella, and your knee starts to feel weak and unstable. Discomfort lingers after exercise, requiring longer recovery periods. The feeling of grinding (crepitus) under your kneecap becomes more noticeable and running or jumping will become increasingly difficult.
In the severe stage, pain is constant, even at rest. Your knee feels stiff and swollen most of the time, and you’ll have sharp pain with even simple movement like bending your knee or standing up. At this point, untreated runner’s knee will severely limit daily activities like driving and walking, requiring medical intervention and rehabilitation.
The longer your ignore your sore knee, the longer it will take to recover when you start treatment.
X-rays
Muscles cannot be seen on an x-ray, so it will not be effective to diagnose a muscle problem. X-rays will however show the integrity and alignment of joints in your knee.
Your physiotherapist can refer you to get x-rays taken if necessary.
Diagnostic ultrasound
Diagnostic ultrasound can be used to show the presence of a muscle tear (muscle strains), inflammation, swelling or simply increased contraction of a muscle (muscle spasms).
If you need an ultrasound, your physio will refer you.
MRI
An MRI scan can image all of the structures in your lower back, including soft tissue, discs, nerves and bones. However, for a muscle problem an image like this is unnecessary and very expensive. If your physiotherapist suspects anything more than just a muscle spasm, you will be referred to the right specialist.
Problems we see when patients come to us with runner’s knee
Chronic Pain and Discomfort
The pain around the kneecap (patella) may become persistent, making everyday activities like walking, climbing stairs, or even sitting for long periods uncomfortable. The condition can worsen, leading to increased inflammation and sensitivity in the knee joint.
Cartilage Damage (Chondromalacia Patellae)
Continuous friction between the patella and the femur may lead to softening and breakdown of the cartilage underneath the kneecap.
This damage can become irreversible, causing long-term pain and difficulty in movement.
Reduced Mobility and Weakness
Untreated runner’s knee can lead to muscle imbalances, particularly in the quadriceps and surrounding muscles. Weakness in these muscles may further strain the knee, making it difficult to return to physical activities.
Increased Risk of Knee Osteoarthritis
Prolonged misalignment and stress on the knee joint may contribute to early-onset osteoarthritis, a degenerative joint disease that causes stiffness, swelling, and chronic pain. This can significantly impact mobility and quality of life in the long run.
Altered Movement Patterns (Compensatory Injuries)
To avoid knee pain, a person may unconsciously change their walking or running gait, which can put extra strain on other joints, such as the hips, ankles, and lower back. This can lead to secondary injuries, including hip bursitis, Achilles tendinitis, or lower back pain.
Loss of Athletic Performance
Without proper treatment, athletes or active individuals may struggle with reduced endurance, speed, and agility due to persistent knee pain and instability.
Physiotherapy treatment
Physiotherapy plays a crucial role in treating Runner’s Knee (Patellofemoral Pain Syndrome) by addressing pain, correcting movement dysfunctions, and strengthening the knee for long-term recovery. A physiotherapist’s expertise ensures a personalized and structured approach to rehabilitation.
Physiotherapy offers a holistic, expert-driven approach to treating runner’s knee by targeting the root cause, not just symptoms. With pain relief, strengthening, mobility work, and movement correction, physiotherapists help runners recover faster, prevent reinjury, and return to peak performance.
Physiotherapists aim to identify the core structures that is contributing to your pain. We use a variety of techniques to desensitize the irritation on the soft tissue that includes exercises to modify.
Remember prevention is better than cure. Speak to The Experts in the field and let us guide you through the process.
Don’t run on your knees if you know you could be over weight
Stretch your quadriceps after every run.
Gradually increase your training intensity and distance
We recommend sticking to the 10% rule. Increase only one of your parameters less than 10% per week. (Time/ Distance/ Pace)
Foam roll your quadriceps, hamstrings and calf muscles.
Make sure you’re running in the correct shoes specifically for your body
Phases of rehabilitation
Should I do squats to fix my runner’s knee?
Although squats are fantastic for building all-over leg strength, these are not great for when you’re experiencing knee pain because they require deep bends of the knee. Instead of bending your knees to start the squad, imagine you’re sitting down in a chair. This causes you to push your hips and upper body back first, releasing some of the tension on your knees. When your thighs are parallel to the floor, make sure your weight is over your heels rather than your toes.
What about lunges?
This is another one you shouldn’t attempt when experiencing knee pain, but should include when you are not in pain. Be sure to keep your core engaged and as you step forward, try to think of your hips moving down towards the floor rather than forwards. Your knee may not go over the line of your toes. Try doing it against a wall until you’re comfortable.’
Can I still run if I have runner’s knee?
It’s safer to consult a physiotherapists opinion to accurately diagnose the problem. The sooner you decrease the irritation on the knee, the faster the healing will begin. At the first sign of pain cut back on your mileage and rather focus on interval training. Avoid any speed or paste training that requires fast acceleration and deceleration. No Hill or decline runs, it would be safer to run on the treadmill until the knee pain has dissipated. You must include a stretching program at the end of your run which includes quadriceps, hamstrings and calf muscles. Foam roll for an even better results.
Other forms of treatment
- General practitioner
- Chiropractic Care
- Shockwave Therapy (Extracorporeal Shockwave Therapy – ESWT)
- Platelet-Rich Plasma (PRP) Therapy: Still considered experimental for runner’s knee.
- Biokinetics
- Hydrotherapy (Water Therapy): Exercising in warm water reduces joint stress while strengthening muscles. Helps maintain mobility and endurance without impact.
- Gait Analysis & Custom Orthotics: Identifies foot misalignment or improper gait mechanics contributing to knee pain.
- Medications (Pain & Inflammation Relief)
- Corticosteroid Injections (Steroid Shots): Too many injections can weaken knee structures and cause long-term damage.
Is surgery an option?
Surgical management is rarely indicated for runner’s knee but may be necessary in severe cases.
Arthroscopic Surgery to remove damaged cartilage or realign the kneecap.
Lateral Release Surgery loosens tight ligaments pulling the kneecap out of alignment.
Realignment Surgery (Tibial Tubercle Transfer) adjusts patellar tracking in severe misalignment cases.
These surgical options are reserved patients with structural knee issues (malalignment, severe cartilage damage). Any knee surgery requires extensive rehabilitation and should only be considered if all other treatments fail.
What else could it be?
Also known as
- Jogger’s knee
- Chondromalacia patella
- Maltracking of patella
- Anterior knee pain
- Patellofemoral pain syndrome
- Kneecap pain
