Knee Pain Location ChartBy Mr. Sam Rajaratnam FRCS (Tr. & Ortho)
Knee pain can vary in degree from being something which is a minor irritation or which causes slight concern to being a major problem impacting on your mobility and way of life.
Technically the knee is a synovial hinge joint, meaning that it is supplied with synovial fluid to lubricate movement and nourish the joint, and also moves forward and backwards like a hinge. However, apart from being the largest hinge joint in the body, it is also unusual in that it has a degree of rotational movement.
The knee is a complex structure consisting of bone, cartilage, muscle, tendon, ligament, synovial fluid and nerves. Knee pain could be the result of a problem with any one of these components, or a combination of several.
You may be experiencing knee pain and want to know the possible causes. The diagram, below, is a handy guide to the possible reasons for your pain.
Pain at the front above the knee
This is the location of the quadriceps tendon which attaches the four large muscles of the front of the thigh to the knee cap.
Possible Causes of Pain
Quadriceps tendonitis – this is caused by the irritation, strain or injury to the quadriceps tendon.
This affects the underside of the kneecap (patella) and the trochlear groove in the femur in which it moves. When the articular cartilage covering the surfaces of the bone wears away and becomes inflamed the bones come into contact with each other resulting in pain.
A plica is the fold in the thin synovial membrane that lines the knee joint. There were four of these folds in the knee joint originally, but they often become absorbed during foetal development. About 50% of the population is thought to have the remains of the embryonic plicae. When a plica becomes inflamed, perhaps because of repetitive knee movement, trauma or twisting, it causes pain and weakness in the knee.
Lateral patellar facet overload syndrome
This refers to dull aching pain underneath, around the sides or below kneecap. It is caused by increased pressure on the lateral facet of the patella. The reason for this is improper tracking, poor alignment or dislocation of the kneecap. The condition is often apparent during repetitive exercise such as climbing stairs.
The knee is a synovial hinge joint, and as such the joint is lined with a synovial membrane. If this membrane becomes inflamed it is called synovitis. It is caused by overuse or trauma and results in repeated bleeds into the joint. If not treated early or correctly the synovial membrane becomes thickened with more blood vessels and becomes swollen and painful. It is also associated with arthritis and gout.
Pain at the knee itself
This includes pain at the front and within the knee.
Possible Causes of Pain
Anterior Cruciate Ligament (ACL)
The ACL runs through the knee, gives it stability and controls back and forward movement. Damage occurs due to twisting, over extension or sudden force through the knee. It is the most common form of sports injury. Symptoms include pain, possible “popping” sound, swelling and instability.
Patellofemoral pain syndrome
This is a general term used for a dull pain in the vicinity of the kneecap and front of the knee. Sometimes known as runner’s knee. Various causes including overuse or misalignment of the kneecap.
A grating feeling and pain at the junction of the thigh and kneecap may be patella chondromalacia. It is caused by the softening and deterioration of the cartilage on the underside of the kneecap or a loose flap of cartilage.
The kneecap should track smoothly in the groove on the lower end of the thigh bone. If this does not happen, the cartilage on the two surfaces may wear away and the bones come into contact with each other causing pain due to arthritis.
Partially dislocated patella
Twisting or trauma could cause the kneecap to move out of the groove in the thigh bone. This produces severe pain and swelling at the front of the knee.
This is caused by over-stretching or putting extra stress on the patellar tendon at the front of the knee. It produces a burning sensation just below the kneecap.
Most common in children or adolescents. This is inflammation of a growth plate just below the knee where the patellar tendon attaches to the shinbone. It produces swelling and a feeling of tenderness and tightness.
This tends to affect active adolescents. It is an inflammation of a growth plate under the attachment of the patella tendon to the kneecap. The symptoms include pain near the bottom of the kneecap accompanied by swelling and tenderness around the kneecap.
The bursae are thin, fluid-filled, sacs at the points of contact between bone and soft tissue. If one of these sacs at the front of the knee becomes inflamed it causes swelling on the knee, tenderness and a dull ache.
Osteoarthritis is a painful condition which commonly affects the knee joint. At first the symptoms may be mild, but eventually surgery may be needed. The articular (also called hyaline) cartilage within the joint breaks down and no longer cushions the bones. Also the synovial fluid no longer lubricates and nourishes the cartilage. The result is pain and stiffness which increases over time.
Bone tumours form when the bone cells (osteoblasts, osteocytes and osteoclasts) divide abnormally in an uncontrolled way forming a lump of tissue. Most bone tumours are benign, but can weaken the bone and make it vulnerable to other problems. However, some are malignant and spread cancerous cells to other parts of the body (metastasis). Symptoms include continuous pain in the bones, local swelling and inflammation.
Inflammatory joint disease
Inflammatory joint disease or inflammatory arthritis is an overarching term for a number of diseases, including different forms of arthritis, which are all characterised by inflammation of the joints and often other tissues too. Many of these diseases are autoimmune disease in which the body’s immune system turns against itself and damages its own tissues. Symptoms include swelling, pain, stiffness and reduced joint function.
Lateral pain (outer side of the knee)
This area is the least liable to give rise to problems, but if pain does occur it may be due to one of the following conditions.
Possible Causes of Pain
This is an inflammation of the tendon which attaches one of the muscles of the hamstring, the biceps femoris, to the back of the knee.
Iliotibial Band Syndrome
Inflammation and irritation of the thick fibrous iliotibial band which runs from the pelvis to the tibia on the outside of the leg. Usually pain is felt on the outside of the leg, but may transfer to the outer side of the hip.
Lateral collateral ligament damage
Trauma, sprain or tear of the ligament on the outer side of the knee. Possibly accompanied by pressure on the peroneal nerve problem and damage to the posterolateral corner of the knee.
Lateral meniscus tear
The menisci are crescent-shaped bands of cartilage which act as shock absorbers for the knee. The lateral meniscus can tear, rip or split in many ways. Symptoms are a sudden pain followed by swelling and difficulty in walking.
Cyst forming pressure on the meniscus
If there is a tear within the meniscus cartilage, synovial fluid can collect and causes pressure on the meniscus. It can be caused by over-rotation of the knee or by trauma. A lump may be visible at the location of the cyst and pain or a burning sensation may result.
The compartment on the outer side of the knee, the lateral femorotibial compartment, contains articular cartilage. If this cartilage starts to wear down and degenerate, extra fluid may be produced and bony osteophytes form. The symptoms include pain, reduced mobility and instability.
Dislocation of the superior tibiofibular joint and possible accompanying peroneal nerve damage
The superior (or proximal) tibiofibular joint is located just below the knee. It is where the outer side of the fibula is joined to the inner side of the tibia. Its purpose is to allow and limit twisting of the leg and facilitate weight transfer between your foot and your body. A fall can trigger partial dislocation causing pain and instability. If the peroneal nerve, which is located at the joint, is damaged it can cause a feeling of pins and needles and numbness at the outer side of the knee.
Tibial plateau fracture
A tibial plateau fracture is a complex injury because it is a fracture at the top end of the shinbone (proximal end of the tibia). It affects the knee by involving the cartilage on the floor of the joint where the knee joint meets the tibia. The fracture can also affect surrounding tissue nerves and blood vessels. The fracture is usually caused by a high or low energy trauma. Symptoms include pain and swelling, possibly accompanied by pins and needles or numbness.
Posterolateral corner injury (PLC)
The PLC is the area below the knee on the outside of the leg at the top of the tibia and fibula to the bottom of the femur. The PLC is a juncture for a number of ligaments and tendons. They work to avoid over extension and give the knee stability. Injury to this area is a common result of trauma caused by sporting accidents. Trauma to the PLC often includes damage to the posterior cruciate ligament and could also affect the common peroneal nerve.
Medial pain (inner side of the knee)
The causes of pain on the medial side of the knee are going to be similar in many cases to that on the lateral side.
Possible causes of pain
Irritation of medial plica
A plica is a fold in the thin synovial membrane that lines the knee joint. There are usually four in each knee, at the embryonic stage, and help to bend the joints easily. About 50% of the population loose their plicae by absorption at the foetal stage. If a plica becomes inflamed because of injury or overuse it can cause pain, swelling or locking of the knee joint.
Medial meniscus tear or loose cartilage
If the meniscus on the inner side of the knee becomes torn or a small piece of cartilage becomes detached or loose it will cause pain, swelling and mobility problems (see lateral meniscus tear).
If the cartilage of the medial femorotibial compartment begins to wear down and degenerate, the production of extra synovial fluid and formation of bony osteophytes cause pain, reduced mobility and instability.
Medial Collateral Ligament damage
The medial collateral ligament is one of the four ligaments which aid stability of the knee joint. It is the most common knee ligament injury. Damage to the ligament could be in the form of a stretch, partial or complete tear, usually caused by an outward (valgus) force on the joint in a lateral direction. Symptoms include pain, stiffness and possibly bruising.
An osteochondral defect is damage and loss of some articular cartilage which affects the underlying bone. Symptoms include pain when putting weight onto the joint, swelling and instability. Causes can include trauma, repetitive strain or loss of blood supply.
Avascular necrosis is the death of bone tissue due to a lack of blood supply. The result is collapse of the bone. The causes include high alcohol intake or long-term use of high-dose steroid medications. Pain can be progressive, perhaps at first only when weight is put on the knee, but eventually the pain can be continuous.
Pain at the back of the knee
Pain in this location is often due to problems with muscles, tendons or ligaments. Other possible reasons for pain at the back of the knee may be associated with synovial fluid or blood vessels.
Possible Causes of Pain
The hamstring is one of three muscles at the back of the leg between the hip and the knee. The hamstring tendon connects the hamstring to the knee. If the tendon becomes inflamed because of overuse a sharp pain is felt at the back of the knee.
Hamstring tear or pull
Overloading the hamstring muscle can cause it to strain, partially tear or tear. Often caused by strenuous exercise. A sharp pain is felt at the back of the thigh.
Popliteus muscle injury
The popliteus muscle is a thin triangular muscle located in the depression at the back of the knee joint, called the popliteal fossa. Exercise or trauma may cause injury to the popliteus muscle. If the muscle is injured you may feel tenderness when rotating your leg inwards.
The well known, sudden, pain of cramp can occur in any of the muscles at the rear of the leg. The muscle involuntarily contracts and becomes tight and painful. Cramp can be caused by muscle fatigue, strain or dehydration, but some causes are not known. Cramp is generally harmless, but might point to an underlying problem such as restricted blood supply.
Posterior cruciate ligament injury
The posterior cruciate ligament is one of the four major ligaments of the knee. It lies within the knee and has attachments at medial condyle of the femur and posterior intercondylar area of the tibia. When injuries occur to this ligament it is usually when the knee is bent. Injuries range from a partial tear to a complete tear accompanied by other ligament damage. Pain is sometimes accompanied by swelling and instability of the joint.
A Baker’s cyst is an excessive accumulation of synovial fluid in an inflamed bursa of the popliteal fossa. Bursae are fluid filled structures between skin and tendon or tendon and bone which reduce friction between the adjacent moving parts. The increased synovial fluid is caused by arthritis or trauma, and the swelling is seen behind the knee causing a feeling of tightness.
Meniscus tear or loose cartilage
Stiffness and pain at the back of the knee may be due to a torn posterior horn of one of the menisci (see medial and lateral meniscus tear). This type of damage is often due to athletic activity and the pain may not be evident until some time later.