Patellar tendinitis is an inflammation of the tendon that attaches the patella (kneecap) to the tibia (shin bone). The most common tendinitis about the knee is irritation of the patellar tendon. Commonly called “jumper’s knee”. This condition is commonly seen in people who play basketball, volleyball, distance running, long-jumping, mountain climbing, figure skating, tennis or high impact aerobics. In many cases, you will notice a sudden onset of aching and pain in the area just below the kneecap after sports or recreational activities. You may notice pain when landing from a jump or when going up and down stairs. There is sometimes pain at rest, particularly after sitting with the knees bent for a period of time. Swelling in the area just below the kneecap is common, as well as a feeling of weakness at the knee when pain is felt.
The patellar tendon becomes inflamed and tender due to overuse. Overuse injuries of the patellar tendon occur when you repeat a particular activity (usually running, jumping or high-impact) until there is micro-failure of the tissue that makes up the substance of the tendon. Swelling, inflammation and pain follows. In the early (acute) stage of patellar tendinitis, the pain and inflammation subside with rest. There may be pain at the beginning of activity, but this pain often disappears after a period of warm-up and then re-appears after the completion of the activity.
If you continue with your activity in the presence of pain, you initially can continue to exercise or perform at a normal level. However, if you continue to exercise and don’t rest, the pain will become more persistent and will be present before, during and after activity. At this stage, you can do permanent damage to the tendon if you continue your activity and it will take a long time to heal.
Anatomy of Patellar Tendonitis
The patellar tendon attaches the bottom of the kneecap (patella) to the top of the shinbone (tibia). When a structure connects one bone to another, it is actually a ligament, so the patellar tendon is sometimes called the patellar ligament.
The patella is attached to the quadriceps muscles by the quadriceps tendon. Working together, the quadriceps muscles, quadriceps tendon, and patellar tendon enable you to straighten your knee.
Types of Patellar Tendinitis
Patellar tendonitis, also known as jumper’s knee or patellar tendinopathy, can be classified into different types based on the severity and stage of the condition. The types of patellar tendonitis include:
Acute Patellar Tendonitis: This type refers to the early stage of the condition and is characterized by inflammation and pain in the patellar tendon. It typically occurs due to sudden or excessive stress on the tendon, such as a sudden increase in activity level or a traumatic event.
Chronic Patellar Tendonitis: Chronic patellar tendonitis refers to a long-standing and persistent condition. It is often the result of repetitive stress and overuse of the patellar tendon, leading to degenerative changes and structural abnormalities within the tendon. Individuals with chronic patellar tendonitis may experience ongoing pain, swelling, and functional limitations.
Patellar Tendinosis: Tendinosis is a term used to describe a degenerative condition of the tendon. In patellar tendinosis, the collagen fibers within the patellar tendon undergo structural changes and degeneration, leading to a loss of tendon strength and integrity. This type is often seen in chronic cases of patellar tendonitis and may require specialized treatment approaches.
Patellar Tendon Rupture: In severe cases, the patellar tendon may completely rupture, resulting in a loss of continuity between the patella and the shinbone. Patellar tendon rupture is a less common but significant complication of patellar tendonitis. It usually occurs due to a sudden force or trauma applied to the knee and may require surgical intervention for repair.
It’s important to note that the classification of patellar tendonitis into these types is not always mutually exclusive, and there may be overlap or progression from one type to another. Proper diagnosis and assessment by a healthcare professional, often including imaging studies and clinical evaluation, are essential for determining the specific type and severity of patellar tendonitis in an individual case.
The epidemiology of patellar tendonitis, also known as jumper’s knee or patellar tendinopathy, reveals that it primarily affects individuals involved in sports and activities that place repetitive stress on the patellar tendon. It is most commonly seen in athletes participating in sports such as basketball, volleyball, soccer, track and field, and gymnastics. The condition tends to occur more frequently in males than females and is most prevalent in individuals aged 15 to 30 years, although it can affect people of all age groups. The incidence of patellar tendonitis is influenced by various factors, including the intensity and duration of physical activity, training techniques, biomechanical factors, and individual susceptibility. Athletes with a history of previous knee injuries or those with certain anatomical variations may be at a higher risk. Overall, understanding the epidemiology of patellar tendonitis aids in identifying high-risk populations, implementing preventive strategies, and optimizing treatment approaches for this common knee condition.
Multiple theories have been proposed for the pathogenesis of patellar tendinopathy, mechanical, vascular, and impingement related. However, the chronic overload theory is the most commonly reported. Repetitive overload on the knee extensor tendons will cause it to weaken progressively, eventually leading to failure. Microscopic failure occurs within the tendon at high loads and eventually leads to alterations at the cellular level, which undermine its mechanical properties. Tendon micro-trauma may cause individual fibril degeneration due to stress across the tendon. As the fibril degeneration becomes ongoing, chronic tendinopathy will ensue.
Examination of the tendon under ultrasound shows three pathologic changes. At first, there will be edema along the damaged tendon fibers. The affected tissue is swollen and thickened but still homogenous. The second is a “stage with irreversible anatomical lesions,” the tendon has a heterogeneous appearance with hypoechoic and hyperechoic images without edema (granuloma). At this point, the tendinous envelope is still more or less well-defined. In the final stage of the lesion, the tendinous envelope is irregular and thickened. Its fibers appear heterogeneous, yet the swelling has disappeared.
What Are the Symptoms of Patellar Tendinitis?
Symptoms normally appear gradually, but can also develop after a bump to the knee.
- Pain is the most common symptom, localised to the front of the knee (pain can be mild or severe).
- Tenderness on the front of the knee.
- The tendon can sometimes feel a little thickened. Some people can experience tightness or weakness in leg muscles (quadriceps).
- Stiffness in the knee can often occur– especially in the morning.
- Some people can also have mild swelling around the knee.
Causes of Patellar Tendinitis
Patellar tendonitis comes from repetitive stress on the knee, most often from overuse in sports or exercise. The repetitive stress on the knee creates tiny tears in the tendon that, over time, inflame and weaken the tendon.
Contributing factors can be:
- Tight leg muscles
- Uneven leg muscle strength
- Misaligned feet, ankles, and legs
- Shoes without enough padding
- Hard playing surfaces
- Chronic diseases that weaken the tendon
Athletes are more at risk because running, jumping, and squatting put more force on the patellar tendon. For example, running can put a force of up to five times your body weight on your knees.
A combination of factors may contribute to the development of patellar tendinitis, including:
- Physical activity. Running and jumping are most commonly associated with patellar tendinitis. Sudden increases in how hard or how often you engage in the activity also add stress to the tendon, as can changing your running shoes.
- Tight leg muscles. Tight thigh muscles (quadriceps) and hamstrings, which run up the back of your thighs, can increase strain on your patellar tendon.
- Muscular imbalance. If some muscles in your legs are much stronger than others, the stronger muscles could pull harder on your patellar tendon. This uneven pull could cause tendinitis.
- Chronic illness. Some illnesses disrupt blood flow to the knee, which weakens the tendon. Examples include kidney failure, autoimmune diseases such as lupus or rheumatoid arthritis and metabolic diseases such as diabetes.
Complications of Patellar Tendinitis
If left untreated or ignored, patellar tendonitis can lead to several complications, including:
Chronic Pain: Persistent pain in the front of the knee, especially during activities like jumping or squatting.
Tendon Degeneration: Over time, the tendon fibers can break down, weakening the structure of the tendon.
Tendon Rupture: In severe cases, the tendon can partially or completely tear, requiring surgical repair.
Decreased Knee Function: Limited range of motion in the knee, making it difficult to fully extend or flex the knee.
Muscle Weakness and Imbalances: Altering movement patterns due to pain can cause muscle imbalances and weakness.
Patellar Tendinopathy: The condition can progress from inflammation (tendonitis) to tendon degeneration (tendinosis).
If you suspect patellar tendonitis or experience persistent knee pain, it’s important to seek medical attention.
During the exam, your doctor may apply pressure to parts of your knee to determine where you hurt. Usually, pain from patellar tendinitis is on the front part of your knee, just below your kneecap.
Your doctor may suggest one or more of the following imaging tests:
- X-rays. X-rays help to exclude other bone problems that can cause knee pain.
- Ultrasound. This test uses sound waves to create an image of your knee, revealing tears in your patellar tendon.
- Magnetic resonance imaging (MRI). MRI uses a magnetic field and radio waves to create detailed images that can reveal subtle changes in the patellar tendon.
Patellar Tendinitis Treatment
Surgery and other invasive treatments are a last resort when treating patellar tendonitis. Treatments typically focus instead on relieving symptoms and strengthening the muscles around the knee. You might try:
Relaxation: The best form of treatment for patellar tendonitis is resting. Don’t participate in regular activities, support your knee, and stay off your feet.
Pain management: You’ll likely need to take pain relievers like ibuprofen or naproxen to manage pain and reduce inflammation. You can also use ice packs to help reduce painful swelling.
Physical therapy: Your doctor will recommend a series of stretches and exercises to strengthen the muscles around your knee.
A patellar tendon strap: A patellar tendon strap supports your knee and patellar tendon enough to reduce stress and relieve pain. It can help your recovery process as you get back onto your feet.
PRP injections: A PRP injection uses a patient’s own blood, puts it in a centrifuge to centralize the growth factors and then injects it back into the affected area of the knee to promote healing.
Surgery: In chronic cases or instances when the tendon has ruptured, you may need surgery.
How to prevent Patellar Tendinitis?
Although it is important to be able to treat patellar tendinitis, prevention should be your first priority. So, what are some of the things you can do to help prevent patellar tendinitis?
Warm-Up properly: A good warm-up is essential in getting the body ready for any activity. A well-structured warm-up will prepare your heart, lungs, muscles, joints and your mind for strenuous activity.
Avoid activities that cause pain: This is self-explanatory, but try to be aware of activities that cause pain or discomfort, and either avoid them or modify them.
Rest and Recovery: Rest is especially important in helping the soft tissues of the body recover from strenuous activity. Be sure to allow adequate recovery time between workouts or training sessions.
Balancing Exercises: Any activity that challenges your ability to balance, and keep your balance, will help what is called, proprioception: your body’s ability to know where its limbs are at any given time.
Footwear: Be aware of the importance of good footwear. A good pair of shoes will help to keep your knees stable, provide adequate cushioning, and support your knees and lower leg during the running or walking motion.
Strapping: Strapping, taping, or knee braces can provide an added level of support and stability to weak or injured knees.
Stretch and Strengthen: Instead of me trying to explain how to do strength and flexibility exercises, I simply found a few YouTube videos (below) that have clear visual examples and good descriptions of how to perform exercises and stretches for the muscles around your hips and knees.
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