Patellofemoral Pain Syndrome

What causes patellofemoral pain

The kneecap glides in a groove at the end of the thighbone as the knee bends. The force through this joint is about 3 to 4 times body weight on stairs and up to 7 to 8 times in deep squats. Pain develops when the load on the joint is more than the tissues can tolerate, either because the load rose suddenly or because the knee's capacity is reduced.

Contributing factors include:

• Training errors: a sudden increase in running mileage, hills, jumping or squatting
• Weak hip muscles: weak gluteal muscles let the thigh rotate inward and the knee collapse inward (dynamic knee valgus), increasing pressure on the side of the kneecap
• Weak or poorly timed quadriceps
• Tight structures: quadriceps, hamstrings, calf muscles or the iliotibial band
• Foot mechanics: excessive flattening of the foot (pronation)
• Kneecap shape or alignment: a shallow groove or high-riding kneecap
• Body weight and previous knee injury

Damage to the cartilage is not required. Many people with PFPS have normal cartilage on MRI, and many people with cartilage changes have no pain.

Symptoms

• A dull, aching pain around or behind the kneecap, usually at the front of the knee
• Pain going down stairs or hills more than up
• Pain when squatting, kneeling, jumping or running
• Pain after sitting with bent knees for a long time, the "moviegoer's sign"
• Grinding, clicking or crackling under the kneecap (crepitus), usually harmless by itself
• A feeling of weakness or the knee briefly giving way because of pain
• Usually no significant swelling

It often starts gradually and can affect both knees.

PFPS vs similar knee problems

"Runner's knee" is a popular name that usually refers to PFPS in runners.

Diagnosis

PFPS is a clinical diagnosis. A doctor or physical therapist will:

• Ask about activities, training changes and what makes the pain worse
• Reproduce the pain with a squat or step-down, and watch how the knee moves
• Press around the kneecap edges and check how the kneecap moves
• Test hip, thigh and core strength and flexibility
• Check the ligaments and menisci to rule out other injuries

X-rays or MRI are not needed for typical PFPS. They are used if there was an injury, swelling, locking, instability, or no improvement after 2 to 3 months of good rehabilitation.

Treatment

Load management

Reduce, but do not stop, activity. Cut back on running distance, hills, stairs, deep squats and jumping to a level that keeps pain at a manageable level (many therapists use 3 out of 10 or less, settling by the next morning). Swap in cycling with a high seat or swimming.

Exercise therapy

Exercise is the most effective treatment, according to international consensus. Combining hip and knee exercises works better than knee exercises alone:

• Hip strengthening: side-lying leg raises, clamshells, side planks, banded side steps, hip bridges
• Quadriceps strengthening: wall sits at a comfortable angle, leg press in a short range, step-ups, straight leg raises
• Progression: as pain allows, move to deeper squats, lunges, single-leg work and then running and jumping drills
• Movement retraining: practicing landing and squatting with the knee over the second toe rather than collapsing inward

Expect 6 to 12 weeks of consistent exercise, 2 to 3 times a week.

Short-term helpers

• Patellar taping or a knee brace can reduce pain in the short term and make exercise easier.
• Foot orthoses (arch supports) can help some people, particularly those with flat feet, for the first 6 weeks.
• Ice after activity and over-the-counter pain relievers such as ibuprofen or acetaminophen (paracetamol), following the label dose.

Passive treatments alone, such as massage, ultrasound or injections, are not recommended without exercise. Surgery is rarely helpful for PFPS.

Outlook

Most people improve significantly within 3 months of starting an exercise program. However, PFPS can be stubborn: up to about half still have some symptoms years later, especially if they return to full load too fast or stop their exercises. Continuing a maintenance strengthening routine helps prevent recurrence.

Prevention

• Increase running distance or training intensity gradually.
• Include hip and thigh strengthening in regular training.
• Maintain flexibility in the thighs and calves.
• Wear supportive footwear and replace running shoes regularly.

Frequently asked questions

What does patellofemoral pain syndrome feel like?

It feels like a dull ache around or behind the kneecap, worse going down stairs, squatting, kneeling, running or after sitting with bent knees for a while. Some people notice grinding under the kneecap or a brief sense of the knee giving way.

What is the best exercise for patellofemoral pain syndrome?

There is no single best exercise. Programs combining hip strengthening (side-lying leg raises, clamshells, bridges) with quadriceps strengthening (wall sits, leg press, step-ups) work best. Starting with pain-free ranges and progressing gradually over 6 to 12 weeks gives the best results.

How long does patellofemoral pain take to heal?

Most people improve noticeably within 6 to 12 weeks of a consistent exercise program. Some take longer, and symptoms can return if load increases too fast. Keeping up strengthening exercises helps prevent recurrence.

Is walking good for patellofemoral pain?

Yes, walking on flat ground is usually fine and helps keep you active. Hills and stairs load the kneecap more and may need limiting until symptoms improve. Reduce distance if walking increases pain that lasts into the next day.

Is patellofemoral pain syndrome the same as chondromalacia patella?

Not exactly. PFPS describes pain around the kneecap, usually without visible cartilage damage. Chondromalacia patella means the cartilage under the kneecap has softened or worn, seen on MRI or arthroscopy. The two overlap and are treated similarly with exercise.