Knee Cap Pain

Written By: Chloe Wilson, BSc(Hons) Physiotherapy
Reviewed by: KPE Medical Review Board

Find out about the most common causes of knee cap pain

Knee cap pain can be caused by a number of things. It may be that the problem is with the kneecap bone itself, with the cartilage that lines it, or tightness or weakness in the surrounding muscles causing it to move incorrectly.

The kneecap aka patella is a small triangle shape bone that sits inside the quadriceps tendon. It rests in a groove on the femur (thigh bone) known as the patellar/trochlear groove and glides up and down in this groove as the knee moves.

The back surface of the kneecap is lined with the thickest layer of cartilage in the whole body. This is because such large forces go through it.  For example when you squat, a force equivalent to eight times your body weight goes through the kneecap.  

But why do we have kneecaps?  The knee cap is functionally important because it increases the leverage at the knee joint.  This increases the strength of the knee by approximately 30% with extension activities like kicking. 

Common Knee Cap Pain Problems

Problems with the patella tend to cause front knee pain. Here you will find a summary of the most common causes of knee cap pain.

To find out more about each one, including detailed information on symptoms, causes, diagnosis and treatment options, click on the relevant links below:

1. Chondromalacia Patella

Knee cap pain occurs most commonly at the front of the knee

Chondromalacia is a common cause of knee cap pain, especially in young adults and adolescents. Thinning of the cartilage that lines the back of the knee cap results in pain at the front.

Chondromalacia tends to be worse when you first get up from sitting or when climbing stairs. It can also cause a grinding/grating sensation.

Chondromalacia patella is usually caused by muscle tightness and weakness, overuse or altered biomechanics in the leg

Find out More: Chondromalacia

2. Runner's Knee

Runner's knee is a very common cause of patellar pain. It can affect anyone from athletes to office workers, despite the name!

Runner's Knee is a common cause of knee cap pain

Runner's Knee is caused by patella maltracking, a problem with how the kneecap moves. This is usually due to muscle tightness, weakness or abnormal biomechanics e.g. foot position.

The symptoms of Runner's Knee tend to come on gradually over time and people typically experience an achy pain around the front of the knee and under the patella.

Runner's Knee tends to be worse after prolonged activity or inactivity and when coming down stairs.

Runner's Knee is also known as anterior knee pain or patellofemoral pain syndrome.

Find out More: Runner's Knee

3. Patellar Tendonitis

More commonly known as Jumper's Knee, this usually results in knee cap pain just below the patella.

Jumpers knee is a common cause of knee cap pain

Patellar tendonitis is caused by damage to the patella tendon from repetitive activities like jumping and kicking.

The most defining symptom of jumper's knee is pain when pressure is applied just below the knee on the tendon.

Knee cap pain from patellar tendonitis also tends to be worse with and after activity and first thing in the morning.

Pain associated with Patellar Tendonitis tends to get gradually worse over time as the tendon and if left untreated, the tendon may tear completely.

Find out More: Jumper's Knee

4. Dislocated Patella

A patella dislocation occurs when the knee cap is forced out of the patellar groove, usually after an injury, or from twisting the knee awkwardly.

One of the more rare causes of knee cap pain is when the patella dislocates out of position

There is usually a visible deformity with a large bulge to the side of the knee, most commonly the outer side. There tends to also be lots of swelling if the kneecap dislocates.

A patellar dislocation is a medical emergency and needs relocating (putting back in place) by a doctor as soon as possible.

Knee cap dislocation is usually accompanied by damage to the ligaments that hold the knee cap in place which can make you prone to dislocating again in the future. Treatment consists of a rehab program and in some cases surgery may be necessary.

Find out More: Kneecap Dislocation

5. Patella Fractures

X-ray showing a patella fracture

With patella fractures, the kneecap gets broken. This tends to occur due to a fall from a height or a massive force through the bone.

There may be one clean break or in most cases, the patella will break into several pieces.

Depending on the severity of the injury, the leg may be put in a brace/cast to prevent movement for a few weeks while the bone heals, or surgery may be required to fix the fragments back together.

If the injury is severe, part or all of the kneecap may need to be removed.

Find out More: Patella Fractures

6. Patella Alta

Patella alta, aka high riding patella, is a rare but potentially serious cause of knee cap pain. With patella alta, the kneecap sits higher than normal in a shallower part of the patellofemoral groove on the thigh bone. This means that the kneecap is less well supported and thus moves excessively which can lead to secondary knee problems.

Instability and kneecap dislocation is common with patella alta. Knee cap pain from high riding patella is worse after prolonged periods of sitting, on stairs, walking up and down slopes and squatting.

Find Out More: Patella Alta

7. Arthritis

Arthritis often causes knee cap pain. Osteoarthritis is when there is wear and tear in the bones and cartilage, which can affect any of the knee bones. Patellofemoral arthritis leads to a narrowing of the space between the kneecap and the groove it sits in on the femur.

Pain from arthritis is usually worse with any activities that put pressure through the patella such as squatting, climbing stairs and kneeling. It also sometimes produces a cracking or grating noise/sensation when you move your knee. 

Find out More: Knee Arthritis

Common Questions

What Causes Pain Under The Knee Cap?

Pain under the kneecap can be due to a number of problems. If the pain is felt on the back of the kneecap it is usually a problem with the cartilage on the back of the patella, most typically Chondromalacia Patella or Runners Knee. The pain tends to come on gradually and gets worse after sitting for a while or doing lots of exercise.

If the pain is felt below the kneecap, the most common causes are patellar tendonitis or infrapatellar bursitis.

What Causes Sharp Pain In The Knee Cap?

Sharp knee cap pain is usually caused by either damage to the cartilage on the back of the kneecap, or a patella fracture - a break in the bone. Sharp knee pain is usually worse with movement and may be intense.

How Do You Treat Knee Cap Pain?

Treatment for patella pain will depend on the type of injury. In most cases, knee cap pain can be treated with a combination of exercises and physical therapy, ice, painkillers and a knee brace. 

Find Out More

If none of these are sounding quite like your pain, visit the knee pain diagnosis section for help working out what is wrong with your knee.

To find out more about these common causes of knee cap pain, including causes, symptoms, diagnosis and treatment options, click on the links above.

  1. Knee Pain Guide
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  3. Diagnosis
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  5. Knee Cap Pain

Page Last Updated: 9/19/19
Next Review Due: 9/19/21

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