Knee pain is a common complaint that affects people of all ages. Knee pain may be the result of an injury, such as a ruptured ligament or torn cartilage. Here is a list of the most critical anatomical principles of a healthy knee joint and an overview of all significant knee joint diseases, including arthritis, gout and infections, which may cause knee pain and conditions.
If your primary care physician has recommended that you meet with a knee specialist for any acute or chronic injuries or conditions you may have, it can be helpful to know what to expect during the initial consultation.
For more detailed information, simply follow the link to the appropriate disease.
Classification of knee joint diseases
Below you will find an overview of the most common diseases of the knee joint, arranged in order:
- Injuries to the ligaments of the knee joint
- injuries to the bony structures of the knee joint
- Illnesses caused by overloading and wear and tear
- Inflammations in the knee
- Specific diseases of the knee joint
Injuries to the ligaments of the knee joint
Meniscus damage and knee pain
Meniscus damage is the injury or tearing of one of the two cartilage discs located between the femur and tibia. The joint surfaces of the femur and tibia do not fit together. To compensate for this “asymmetry”, we have “cartilage discs” in the joint, an inner and an outer meniscus. Meniscus damage may cause the knee to be imbalanced and cause a knee clicking noise or sensation.
Read more about Meniscus damage: Symptoms and Treatment
Anterior cruciate ligament rupture condition
A fresh anterior cruciate ligament rupture is the complete or partial interruption (rupture) of the continuity (tear) of the ligament after the overstretch an external force has exceeded reserve. An old anterior cruciate ligament rupture is a permanent, mostly accident-related ligament injury. Typically, such an injury can occur when the lower leg is fixed while skiing or playing football.
Read more about Anterior cruciate ligament rupture: Symptoms and Treatment
Rupture of the posterior cruciate ligament
A fresh posterior cruciate ligament rupture is the complete or partial interruption of continuity (tear) of the ligament after the overstretch an external force has exceeded reserve. An old posterior cruciate ligament rupture is the permanent, mostly accident-related ligament damage.
Read more about Posterior cruciate ligament rupture: Symptoms and Treatment
Torn outer strip may cause knee pain
Injuries to the outer ligament are usually a tear of the same. In most cases, the tear is complete – there are hardly any incomplete tears. The cause is usually a trauma (rotation, dislocation). Depending on the extent of the injury (rupture of the external ligament), the therapy may vary from immobilization for a few days to surgery. The prognosis is usually good.
Inner strip breakage
Injuries to the inner ligament are usually a tear of the same. In most cases, the tear is complete – there are hardly any incomplete tears. The inner ligament usually only tears as a result of trauma. This can be a kink, a rotational trauma, or a dislocation of the knee joint, as it occurs, for example, when skiing or playing football. The therapy of an inner ligament rupture depends on the extent of the injury.
Ligament elongation and knee pain
Ligament stretching (syn. ligament strain) of the knee is caused by a violent movement of the knee joint beyond the usual extent and can affect both the inner and outer ligament. It is one of the most common sports injuries and can be caused, for example, by a sudden rotational movement of the knee.
Read more about Ligament stretching in the knee: Symptoms, and Treatment
Torn patella tendon is a serious knee condition
A torn patella tendon is when the tendon between the front thigh muscles and the lower part of the patella tears partially or entirely. A rupture of the patellar tendon usually occurs spontaneously due to excessive over-tensioning of the leg against resistance or when the knee is tensed in the flexed position. Those affected usually express a sudden pain.
Read more about Torn Patella Tendon: Causes, Symptoms, and Treatment
Injuries to the bony structures of the knee
Patella fracture and knee pain
In the case of a patella fracture, the patella fractures into several parts and can result in longitudinal, transverse, or mixed fractures. The therapy of a patella fracture/patella fracture depends crucially on the type of fracture. A doctor should be consulted for further diagnosis.
Read more about Patella fracture, symptoms, tests and treatment
Reasons for a shin bone contusion are very catchy. One usually gets a bruise on the shin bone by striking the shin bone or kicking against a rigid or solid object that cannot give way. The classic symptoms of a shin bruise are pain, swelling, a bruise, and some restriction of movement.
Read more about Shin bruise, causes, symptoms and treatment
Illnesses due to overloading and wear and tear
Cartilage damage in the knee
Cartilage damage in the knee occurs quite frequently. Mostly the damage here is caused by wear and tear. On the one hand, this wear occurs as part of a completely natural aging process. The result of this process is called arthrosis by experts. First of all, all risk factors must be eliminated or reduced as far as possible.
Read more about Cartilage damage in the knee: Symptoms and Treatment
Jumper Knee can cause knee pain
The jumper knee is a chronic, painful, degenerative overload disease of the patellar extensor apparatus at the bone/tendon transition of the patella tip. It is also known as “patellar tip syndrome.” Patients report a load-dependent pain in the area of the tip of the patella.
Read more about Jumper`s knee: Causes, Symptoms, and Treatment
Knee joint arthrosis
The term gonarthrosis/knee joint arthrosis refers to all degenerative (wear-related) diseases of the knee joint, which are characterized by increasing destruction of the joint cartilage with the joint structures such as bones, joint capsule, and muscles close to the joint being involved. It can have several causes and is usually initially manifested by initial pain and swelling.
Read more about Knee joint arthrosis / Gonarthrosis: Symptoms and Treatment
In the typical patella dislocation, the patella jumps out of the intended slide path, and it can lead to injuries of ligaments, cartilage, and bones. The symptoms of a patella luxation (dislocation of the patella) are usually so typical that they enable the trained physician to make a gaze diagnosis. In most cases, a patellar dislocation does not require any treatment, as it usually returns to its plain bearing by itself
Read more about Patellar dislocation: Causes, Symptoms, and Treatment
Shelf syndrome occurs after overuse, muscle imbalance, or injury to the knee. It is caused by inflammation and swelling of the mucosal folds (synovial folds, plicae) in the knee joint. This can lead to pain and restricted movement in the knee joint.
Three mucous membrane folds of the knee can be affected: the suprapatellar plica, the mediopatellar plica, and the infrapatellar plica. However, the mediopatellar plica is by far the most frequently affected.
Read more about Knee Plica Syndrome: Causes, Symptoms, and Treatment
Inflammations in the knee that causes knee pain
Like almost any other organ, the kneecap can also become inflamed. This can lead to considerable pain and restricted movement in the knee joint. The main symptom of an inflammation of the knee joint is knee pain, especially in the front part of the knee joint and above/below the kneecap directly. The most frequent cause of an inflammation of the kneecap is overstrained.
Read more about Patellar tendonitis: Causes, Symptoms, and Treatment
Inflammation of the quadriceps tendon usually results from chronic overloading of the tendon and all structures connected to it. The affected person becomes aware of it primarily through a point-like pressure pain exactly above the corresponding tendon section. Conservative therapy can be considered at the beginning as a treatment for inflammation of the quadriceps tendon.
Read more about Quadriceps Tendonitis: Causes, Symptoms, and Treatment
Specific diseases of the knee joint that causes knee pain
The disease known as Sinding-Larsen’s disease is an extremely painful inflammatory reaction in the area of the knee joint. The majority of patients affected are young people. Sinding-Larsen’s disease occurs more frequently in athletes. The treatment of Sinding-Larsen’s disease is divided into non-operative and operative measures.
Read more about Sinding-Larsen’s disease: Causes, Symptoms, and Treatment
Arthrofibrosis can cause knee pain
Arthrofibrosis is a dreaded joint disease, the cause of which is largely unexplained, following surgery or injury, resulting in a more or less severe, sometimes painful, restriction of joint mobility. A distinction is made between primary arthrofibrosis, which is characterized by generalized scarring in the joint, and secondary arthrofibrosis, in which local mechanical irritations are the cause of limited movement.
Read more about Arthrofibrosis: Causes, Symptoms, and Treatment
Osgood disease – Schlatter
Osgood-Schlatter’s disease is a painful irritation of the insertion of the patellar tendon at the front of the tibia, and it leads to detachment and death (necrosis) of bone fragments from the tibia. This results in a dead bone area. Osgood-Schlatter’s disease may be a reason for aseptic osteonecrosis, which is not caused by bacteria, viruses, or others.
Read more about Osgood-Schlatter disease: Causes, Symptoms, and Treatment
A Baker cyst is a protrusion of the posterior joint capsule caused by internal knee diseases with chronic knee joint effusion. A Baker’s cyst is particularly common in older people due to wear and tear of the knee joint and in children (usually without a clear cause). A doctor can generally make the diagnosis of a Baker’s cyst.
Read more about Baker`s cyst: Causes, Symptoms, and Treatment
Osteochondrosis dissecans (OD) is a disease that frequently occurs during growth and young adulthood and affects the knee joint in approximately 85% of cases. In the course of this disease, bone death occurs close to the cartilage, whereby a piece of cartilage located above the affected bony region can detach from its bond.
Read more about Osteochondrosis dissecans: Causes, Symptoms, and Treatment
Patellofemoral pain syndrome
Pain in the kneecap is also known as femoropatellar pain syndrome (PFPS). PFPS is one of the most common symptoms in the anterior knee area. Behind PFPS, there is no unified clinical picture but a very complex symptom, which is discussed very differently in terms of definition, diagnosis, and etiology (causes).
Read more about Patellofemoral Pain Syndrome: Symptoms, and Treatment
General information about the knee joint
Here you will find more information about the structure and function of the knee joint and common symptoms.
The anatomical structure of the knee joint
The knee joint is the largest joint in the human body and represents the movable connection between the upper leg (femur) and the lower leg (tibia). Three bones, together with a sophisticated capsule and ligament apparatus (collateral and cruciate ligaments), form the framework of the knee joint.
- the femoral rolls (femoral condyles)
- the head of the tibia (tibial plateau)
- the kneecap (patella)
The figure above shows that the bones are in close contact with each other. So that pain-free and undisturbed mobility of the knee joint can also take place at the contact surfaces, the bones at the respective contact surfaces are covered with a very smooth, whitish cartilage layer, the so-called hyaline cartilage.
Only through this layer is painless and undisturbed mobility of the knee joint possible. The hyaline cartilage is composed of cartilage cells and matrix tissue. While adult cartilage cells have lost the ability to divide and thus to heal, child cartilage cells can repair cartilage wounds by multiplying.
The cartilage cells are embedded in the matrix tissue they produce themselves. This consists mainly of water and supporting tissue and gives the cartilage tissue both stability and elasticity.
In the knee joint itself, a distinction is made between the femoral condyle and the kneecap (femoropatellar joint) as well as the femoral condyle and the tibial head. The connection between the femoral condyle and the kneecap (patella) is the most heavily loaded part of the knee joint. When climbing stairs, for example, this joint is loaded with more than three times the body weight.
The most important tendon of the knee joint is the patellar tendon (patella tendon/patellar tendon), which pulls from the kneecap at the front of the knee joint as a strong cord to the tibia.
The knee joint is encased by the knee joint capsule, the inner part of which is called the synovial membrane. It forms the synovial fluid that is important for the nutrition of the cartilage. In adulthood, cartilage tissue is mainly nourished by diffusion (passive transport) from the synovial fluid because cartilage tissue, unlike other tissues of the body (muscles, bone skin, etc.), is not supplied with blood.
The usual nutrition via the bloodstream, therefore, does not work.
Movements of the knee joint mix the synovial fluid and thus improve the absorption of nutrients by the cartilage cell (chondrocyte).
The correct amount and composition of the synovial fluid is also crucial for the lubrication of the knee joint. It minimizes friction between the corresponding cartilage surfaces during movement. Hyaline cartilage has a little frictional resistance, lower than all known artificial material pairings.
Between the femoral condyle and the lower leg, there are two fibrocartilaginous discs (meniscus), which act as a buffer between the cartilage surfaces and are important for even pressure distribution in the knee joint under load. The cruciate ligaments run through the knee joint and connect the thigh with the lower leg. The main task of the cruciate ligaments is to ensure a stable knee joint and thus to enable a harmonious, low-friction movement sequence.
The two cruciate ligaments prevent the knee from shifting forward (anterior cruciate ligament) or backward (posterior cruciate ligament) under load. In their stabilizing effect, they are supported by the collateral ligaments (collateral ligaments), the knee joint capsule, and the knee-clamping muscles.
The knee-clamping musculature makes up the function of the knee joint. It is only through these muscles that movement is possible. They also support the passive joint stabilizers of the capsule-ligament apparatus. The extensor muscles of the knee joint (quadriceps muscles) on the front of the thigh are very strong. The muscles are involuntarily activated when the knee joint is flexed to avoid buckling when walking. The most important flexors of the knee joint are the hamstring muscles on the back of the thigh, which also have an active stabilizing effect on the knee joint. The hamstring musculature supports the anterior cruciate ligament in particular, which is why its training is particularly important after a torn cruciate ligament.
Knee pain can be subdivided according to where it occurs on the knee.
Knee pain on the inside of the knee can indicate a lesion of the medial meniscus or the medial ligament. Besides, it often occurs as a result of wear and tear, for example, in the case of knee joint arthrosis on the inside of the knee joint. Incorrect strain when walking due to unsuitable footwear, malposition of the feet or leg axis, and a difference in leg length can cause pain on the inside of the knee. You can also feel knee pain when squatting or going upstairs.
The same applies to the outside of the knee joint. Pain localized there (see: external knee pain), in contrast to pain on the inside, is more indicative of involvement of the external ligament or the external meniscus.
Arthrosis of the knee joint can also be the cause of this if it rather affects the outer knee joint area. In acute injuries of the menisci or ligaments, the pain is usually sharp, sudden, and often accompanied by other symptoms such as swelling or overheating of the joint region and joint effusion.
In degenerative processes, such as arthrosis, the pain usually develops over a longer period and occurs mainly when the joint is under stress.
Knee pain that is mainly concentrated in the hollow of the knee (see: Pain in the hollow of the knee) can also have different causes. For example, pain in the popliteal fossa can occur when the rear part of a meniscus is injured. Inflammation or alteration of muscle tendons and knee joint arthrosis in this area can also explain the symptoms.
In the case of arthrosis or damage to the meniscus in the joint, a so-called Baker cyst can develop over time. This is a bulge in the joint capsule that is filled with fluid. Once it reaches a certain size, the Baker cyst can be felt as a swelling in the hollow of the knee and can also cause pain there.
If pain is felt in the hollow of the knee, a thrombosis – a blood clot – in the blood vessels of the lower leg must always be considered.
Knee pain can also be located behind the kneecap. This is typical for so-called retropatellar arthrosis, an arthrosis that develops directly behind the patella. A muscular imbalance or congenital deformation of the patella can also cause pain behind the patella, as the patella is then unable to slide in the bone groove provided for it. This leads to friction and wear and tear in the joint and, secondarily, to pain.
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