What can cause a sharp stabbing pain in the knee?

Although a relatively simple hinge joint that simply extends and flexes to bend and straighten the leg, the knee is actually quite complex. It is made up of 4 main ligaments (the anterior cruciate ligament, posterior cruciate ligament, medial collateral ligament and lateral collateral ligament), the patella tendon(s), menisci and several bursae; amongst a number of other smaller connective structures. Being a relatively small joint but having to absorb and stabilise a lot of weight, makes it both susceptible to injury and complex to rehabilitate once injured.

Although most knee injuries are either relatively minor and don't last long, or quite obviously severe enough to require surgery; there are a few that sit in a little grey area in between which are minor in the grand scheme of things, but also can take a while to "fix", which can be quite frustrating!

Once particular area that can be quite tender and frustratingly easy to irritate, is the front of the knee. The knee cap sits over the joint and helps with movement and protection of the joint. There are a few delicate structures around it which can be painful if inflamed. To understand your type of pain more easily, it helps to know how the knee joint is made up and how each part can become "injured".


The Anatomy of the Knee Joint

The knee joint, a marvel of human biomechanics, is a complex and crucial hinge joint connecting the femur (thigh bone) to the tibia (shin bone) and the patella (kneecap). Its anatomy consists of several key components. Articular cartilage lines the ends of these bones, providing a smooth, low-friction surface for movement. Ligaments, such as the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL), stabilise the joint, while the medial and lateral menisci act as cushioning pads within the joint, absorbing shock and distributing weight. Muscles, including the quadriceps and hamstrings, play a pivotal role in knee movement and stability. Synovial fluid lubricates and nourishes the joint, ensuring its smooth operation. A network of bursae, small fluid-filled sacs, reduces friction between tendons and bones. This intricate combination of structures allows the knee joint to perform its essential functions, including flexion, extension, and rotation, making it a vital component of our daily activities and mobility.


Chronic overuse injuries vs acute traumatic knee injuries

Acute traumatic knee injuries and chronic overuse injuries represent two distinct categories of knee-related problems, each with its own set of characteristics and causes. Acute traumatic knee injuries typically result from sudden and forceful incidents, such as falls, collisions, or sports-related impacts. These injuries can range from ligament sprains and muscle strains to more severe conditions like ligament tears, meniscus tears, or dislocated kneecaps. They often present with immediate pain, swelling, and limited range of motion.

On the other hand, chronic overuse injuries develop gradually over time due to repetitive stress and strain on the knee joint. Activities like running, jumping, or even excessive sitting can contribute to these injuries. Conditions like patellar tendonitis, iliotibial band syndrome, or patellofemoral pain syndrome are common examples. Chronic overuse injuries typically manifest as persistent, nagging discomfort, localised pain, and swelling that worsens with activity and tends to improve with rest and conservative treatments.

Understanding the key differences between these two types of knee problems is crucial for accurate diagnosis and appropriate management, as treatment approaches can vary significantly depending on the nature and underlying causes of the problem.


The most common causes of anterior knee pain

There are many potential causes that can lead to different types of knee pain. The most common symptom is pain itself but others include restricted range of movement, inflammation of the joint, a dull ache, sometimes bruising and in severe cases locking of the joint itself.


Knee Bursitis

Knee bursitis is a painful condition characterised by inflammation of one or more of the bursae surrounding the knee joint and is the most likely cause of sharp knee pain. A bursa is a small, fluid-filled sac that serve as cushions and lubrication points between bones, tendons, and muscles, reducing friction during movement. In the knee, several bursae exist, and each can become inflamed, leading to different types of knee bursitis.

The most common type of knee bursitis is prepatellar bursitis, which occurs when the bursa in front of the kneecap (the prepatellar bursa) becomes irritated and inflamed. This condition is often referred to as "housemaid's knee" because it can develop due to prolonged kneeling or repeated pressure on the front of your knee. This can present as a sharp stabbing pain at the front of the knee caused by the inflammation of the bursa.

Another type is infrapatellar bursitis, which affects the bursa just below the kneecap. It can result from overuse or trauma and is sometimes called "clergyman's knee."

Pes anserine bursitis affects the bursa on the inner side of the knee, near the pes anserinus tendon attachment. This type is often associated with activities that involve repetitive knee bending, such as running or cycling where the repetitive movements lead to an inflamed bursa.

In addition to these, there are other less common forms of knee bursitis that can affect various bursae around the joint. Regardless of the specific type, knee bursitis typically presents with symptoms such as pain, swelling, warmth, and tenderness in the affected area. Rest, anti-inflammatory medications, ice, and physical therapy are common treatment approaches, although more severe cases may require aspiration to remove excess fluid or, in rare instances, surgical intervention to remove the bursa. Proper diagnosis and treatment are essential to relieve pain and prevent long-term complications.


Patella Tendinopathy

Patella tendinopathy, also known as patellar tendinitis or "jumper's knee" or "runner's knee", is a painful condition characterised by the inflammation and degeneration of the patellar tendon, which connects the kneecap (patella) to the shinbone (tibia). This condition is essentially the inflammation of the tendon that attached your kneecap to your shin and often afflicts athletes, especially those involved in sports that require frequent jumping and explosive leg movements, such as basketball or volleyball. The repetitive stress placed on the patellar tendon can lead to micro tears, resulting in pain, swelling, and stiffness in the front of the knee, just below the kneecap. Patella tendinopathy is typically an overuse injury, and its severity can range from mild discomfort to a debilitating condition that hinders athletic performance.

Treatment options often include rest, ice, physical therapy to strengthen the quadriceps and improve biomechanics, and anti-inflammatory medications. In more severe cases, shockwave therapy, corticosteroid injections, or, rarely, surgical intervention may be considered to alleviate symptoms and promote healing. Managing patella tendinopathy requires a comprehensive approach that includes addressing contributing factors like muscle imbalances, training errors, and biomechanical issues to prevent recurrence and support a full return to activity.


Osgood-Schlatter Disease

Osgood-Schlatter disease, often referred to as OSD, is a common musculoskeletal condition that primarily affects the adolescent age group, especially those who are active in sports or physical activities. It is characterised by pain and inflammation at the site where the patellar tendon attaches to the tibia, just below the kneecap. OSD typically occurs during the adolescent growth spurt when bones are growing rapidly. The repetitive stress from activities like running, jumping, and sports can lead to small microtears and irritation at the patellar tendon's insertion point on the tibial tubercle, resulting in pain, swelling, and tenderness.

Symptoms of OSD often include knee pain that worsens with physical activity, especially activities that involve bending or straightening the knee, such as running, jumping, or climbing stairs. The pain is usually relieved with rest. A bony prominence or lump may also develop at the tibial tubercle, where the tendon attaches, although this usually resolves as the adolescent's bones finish growing.

Treatment for Osgood-Schlatter disease focuses on relieving pain and minimising inflammation. Rest from aggravating activities, ice application, and over-the-counter pain medications are commonly recommended. Physical therapy can help strengthen the surrounding muscles and improve flexibility. In most cases, OSD resolves on its own once the adolescent's bones stop growing, typically by the late teenage years. However, in severe cases or when symptoms persist into adulthood, further evaluation and treatments such as bracing or corticosteroid injections may be considered. While Osgood-Schlatter disease can be uncomfortable, it rarely leads to long-term complications, and most individuals can return to their usual activities once the condition resolves.


Meniscus Tear

Meniscus tears are a prevalent and often painful orthopedic knee injury that occurs when the meniscus, a C-shaped wedge of cartilage in the knee joint, gets damaged or torn. The menisci are vital for knee stability and play a crucial role in load-bearing, shock absorption, and joint lubrication. These tears can happen due to a sudden traumatic event, like a sharp twist or pivot while bearing weight, or as a result of degeneration over time, especially in older individuals.

Meniscus tear symptoms may include severe pain, swelling, stiffness, and a sensation of catching or locking in the knee joint. In some cases, individuals may experience difficulty fully extending or flexing the knee. The severity and type of meniscus/cartilage tear can vary, with common types including longitudinal, radial, and bucket-handle tears, each with its own characteristics and treatment implications.

Treatment for meniscus tears depends on several factors, including the tear's size, location, and the individual's age and activity level. In many cases, conservative approaches like rest, ice, compression, and physical therapy can help alleviate symptoms and promote healing. However, larger or complex tears may require surgical intervention, often using minimally invasive arthroscopic techniques to repair or trim the damaged meniscus. Recovery from meniscus surgery can take several weeks, followed by physical therapy to restore strength and range of motion.

Managing meniscus tears promptly and effectively is essential to prevent long-term complications like osteoarthritis, as the menisci play a crucial role in the knee's overall health and function. Early diagnosis and appropriate treatment tailored to the individual's specific condition are key to a successful recovery and the preservation of knee joint function.


How to treat anterior knee pain

To treat any knee pain effectively, it's important to know exactly what you are trying to treat. Going through a physical exam with a healthcare provider like a physiotherapist or a sports therapist will help you diagnose the cause of your pain. Although some of the treatment approaches do cross over between injuries, there are some distinct differences between each injury.

A qualified medical professional may also consider a cortisone injection which aims to help reduce any inflammation in the affected area. This is not a quick fix, but should be seen as a window of opportunity which settles your symptoms down so you are able to do some rehabilitation exercises as part of a structured programme in order to address the cause of your injury.

Generally, applying an ice pack to any area of inflammation might provide some analgesic effects and help with pain. If you've just suffered the injury, it might also help to speed up your recovery time. Wearing a knee brace could also help to minimise additional movement, manage swelling and provide some support to the tibiofemoral joint, however you should check with a physical therapist first because limiting movement isn't always the best approach.

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Arun Gray sports therapist strength and conditioning coach skegness

The author

Arun Gray is a sports therapist and strength & conditioning coach with over 15 years experience in the industry. He also has a personal history with chronic shoulder and back pain along with a range of other sporting injuries.

Arun writes about common injuries and aims to help people understand and manage their pain to prevent having to rely on national healthcare.

Read more about Arun