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Pain at the front of the knee, what are the causes?

What are the causes of pain at the front of the knee?

Pain at the front of the knee is not uncommon, particularly in active people. Pain coming from the knee cap (patellofemoral joint) would be the most common cause of pain here, but there are other less common causes.


Patello-femoral joint arthritis (osteoarthritis)

The patellofemoral joint is the part of the knee behind the kneecap. Arthritis due to wear and tear can result in thinning or loss of the articular cartilage. This leads to increased stress upon the bone and usually results in pain felt at the front of the knee (just behind the knee cap). Sometimes, the pain can be hard to pinpoint and felt as deep pain within the knee. The pain can worsen after periods of inactivity and can be associated with clicking. Management depends on the severity of arthritis and desired outcome but usually consists of physiotherapy and strengthening exercises. Ultrasound-guided steroids, Hyaluronic acid and PRP injections can be useful for management. You can find out more about Patellofemoral joint osteoarthritis here.



Chondromalacia patellae

In this condition, there is thinning to the patella (knee cap) cartilage only, while the articular cartilage covering the other bone (the femur) is preserved. The cartilage thinning usually affects small areas within the patella resulting in small fissures. These can result in pain at the front of the knee. It can be seen in young people who do repetitive activities that put increased stress upon the patella (like running and cycling). MRI is very useful in the assessment here as the patella cartilage is deep and difficult to assess on ultrasound. The MRI will be very useful to assess any subtle changes to the articular cartilage and bone and help establish the diagnosis. It will also assess the shape of the joint as abnormal anatomy can sometimes put excess stress upon the patella and lead to cartilage thinning and sometimes impingement of the fatty tissue around the knee. The latter is referred to as fat pad impingement. Overall, the management of Chondromalacia patellae is conservative consisting of physiotherapy, strengthening exercises and activity modification.


Patellar tendinosis

Patellar tendinosis is not an uncommon cause of pain at the front of the knee. It can be seen in people who get involved in repetitive overuse activities like jumping. This tendon connects the patella (knee cap) to the upper part of the tibia (the shin bone). The pain in this condition is located just under the kneecap. The high-intensity activities that involve jumping will lead to increase stress on the tendon resulting in tendon thickening and inflammation. This is referred to as tendinitis or tendinosis. The treatment usually consists of physiotherapy, activity modification, and sometimes PRP injections can be useful in the management. To find out more, please read our article about Patellar tendinosis. A knee ultrasound examination is very useful in establishing the diagnosis and guiding the treatment.


Fat pad impingement

The knee fat pad is a cushion of fatty tissue located below the patella (knee cap) and behind the patellar tendon (which runs from the knee cap to the shin bone). It is also referred to as the Hoffa’s fat pad or the infrapatellar fat pad (because of its location below the patella). Knee fat pad impingement occurs if the fat pad is pinched between the patella (knee cap) and the lateral femoral condyle (the lower end of the thigh bone). This will lead to inflammation, swelling, pain, and sometimes scar tissue formation. The knee fat pad contains a high number of nerve endings which makes it sensitive to pain. To find out more, please read our article about fat pad impingement.



Other less common causes of pain at the front of the knee include:


Quadriceps tendinosis

This tendon attaches to the top of the knee cap (patella) and is formed by the quads muscles. Tendinosis (inflammation) here is uncommon but can cause pain above the patellar. Inflammation here can be associated with inflammatory arthritis (like rheumatoid arthritis). The quadriceps tendon is also susceptible to injury, especially in forceful extension, which can put extra pressure on the tendon, leading to a ligament tear.


Pre-patellar bursitis

This refers to inflammation of a small sac (called the prepatellar bursa) located at the front of the knee cap, just underneath the skin. Sometimes, it is called (Housemaid’s knee), as it is usually associated with kneeling activities. This would irritate the bursa leading to inflammation and fluid build-up. Treatment usually involves avoiding activities that involve putting pressure on the knee cap, and sometimes ultrasound-guided aspiration can be useful. To find out more, please read our article about Prepatellar bursitis


Gout

Gout is a form of arthritis that can affect the joint. It results from depositing special material (called urate crystals) within the joints and soft tissues. It can affect the knee but is commonly seen in the big toe. It can involve the patellar tendon (the tendon that connects the knee cap to the upper part of the tibia (the shin bone), leading to pain and swelling of the tendon. It can result in significant soft tissue swelling, which could be mistaken for a sinister lesion. Diagnosis of gout nowadays is best done using a special type of CT examination (dual-energy CT).


Summary

Pain at the front of the knee is usually caused by a problem arising from the patella (the knee cap) or the tendon underneath (the patellar tendon). Problems in this area can happen due to overuse or degenerative changes/osteoarthritis. The article describes the most common causes of pain at the front of the knee.



Knee conditions and treatment

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