Knee pain is one of the common complaint that people seek consultation for.
Knee pain can be acute or chronic. Acute knee pains can be caused by an acute injury or infection. Chronic knee pains are often from injuries or inflammation but can also be caused by infection.
Chronic pain is generally result of a long-standing medical condition or damage to the body.
Anatomy of the Knee
Knee joint is formed by femur bone above and tibia below. Patella is a sesamoid bone that is present in the tendon of quadriceps on the anterior aspect of knee and forms patellofemoral part of knee joint. The main joint is between tibia and femur. The fibula is not directly involved in the knee joint but is close to the outer portion of the joint.
The knee is more than just a simple hinge. It also twists and rotates. A number of structures support and stabilize the knee which includes bones, ligaments, tendons, and cartilage.
Ligaments are fibrous bands that connect bones to each other. Four important ligmanents of knee joint are anterior cruciate ligament, posterior cruciate ligament, medial collateral ligament and lateral collateral ligament.
Tendons are glistening fibrous bands between muscle bellies and bone. They connect muscles to the bones. bands similar to ligaments.
Quadriceps is the large muscle in front of thigh and functions to extend the knee. Tendon of quadriceps is the largest tendon which is connected to tibial tuberosity. In between, a sesamoid bone called patella is present and adds leverage to quadriceps function. Patella also acts as stabilizer anteriorly. The part of the tendon between patella and tibial tuberosity is called patellar tendon. Commonly, the term quadriceps tendon denotes the part connecting to patella.
Menisci are cartilaginous structures that cushion the knee joint. Two menisci, lateral and medial are present. They provide both space and cushion for the knee joint.
Bursae are fluid-filled sacs that help to cushion the knee. The knee contains three important groups of bursae.
- The prepatellar bursa lies in front of the patella.
- The anserine bursa is located on the inner side of the knee about 2 inches below the joint.
- The infrapatellar bursa is located underneath the patella
[Read more about detailed anatomy of knee ]
Causes of Knee Pain
Injuries can lead to fracture of the knee bones. For a fracture to occur substantial force is required to break the bone.
Fractures lead to severe pain acutely and are often accompanied by significant soft tissue injury. The patient typically is not able to bear weight after the injury when fracture is there.
Injury is an emergency and should be accordingly dealt. Fractures around the knee could be associated with vascular and/or neural injuries.
Dislocation of knee and dislocation of patella are common types of dislocations. Dislocation of the knee occurs with a severe trauma and may be limb-threatening because of vascular injury being commonly associated. The dislocation of knee causes severe ligament, artery and nerve injury.
Knee dislocations are very painful and lead to grotesque deformity of the knee. Dislocations require urgent reduction. Sometimes, the reduction may occur spontaneously.
Dislocation of patella is caused by direct trauma or forceful straightening of the leg. Patellar dislocation is more common in women, the obese, knock-kneed people, and in those with high-patella.
Ligament injury can occur with twisting forces. Ligaments could injure without injury being caused to bony structures. Medial collateral ligament is the most commonly injured ligament in the knee. Severity of ligament injury may vary from partial to complete.
Anterior cruciate ligament injury is a common sports injury generally due to twisting of knee.
Posterior cruciate ligament is stronger and less commonly torn.
Both ligaments are crucial for knee stability and knee instability results when injury occurs to cruciate ligaments.
Ligament injuries are common in contact sports.
With the patient recumbent, the knee should be partially flexed and the foot stabilized on the examining surface. The examiner should manually attempt to displace the tibia anteriorly or posteriorly with respect to the femur. If anterior movement is detected, then anterior cruciate ligament damage is likely. Conversely, significant posterior movement may indicate posterior cruciate damage. Contralateral comparison will assist the examiner in detecting significant anterior or posterior movement.
Quadriceps and patellar tendons are most common tendons to rupture. The rupture could be traumatic or degenerative [occurs in athletes> 40 years of age]
Tendon rupture could also occur following multiple steroid injections in the tendon.
Following rupture, there is anterior knee pain especially on extension of knee. A patient with complete rupture would not be able to extend the knee though pain could lessen after some time.
Tendon ruptures generally require surgical repair.
Injuries to menisci can lead to knee pain, especially on movement and weight bearing.
Mensical tears may cause the knee to lock, produce clicking and grounding sound during movement of knee.
Meniscal injuries in young require surgical repair, often arthroscopically. A recent study has indicated that exercise therapy is as effective as arthroscopy in case of degenerative tear. A positive McMurray test may indicate a meniscal tear.
The knee is first flexed at 90 degree, and the leg is then extended while simultaneously the lower extremity is torqued medially or laterally. A painful click during inward rotation may indicate a lateral meniscus tear, and pain during outward rotation may indicate a tear in the medical meniscus.
Damage to the cruciate ligaments should be suspected if there is pain of acute onset, possibly with swelling, a history of trauma, or a synovial fluid aspirate that is grossly bloody. Examination of the cruciate ligaments is best accomplished by eliciting a drawer sign.
Osteoarthritis is a degenerative arthritis caused by age related changes in the knee cartilage. Obesity, trauma and infection of the joint may accentuate the degeneration of the knee cartilage.
Osteoarthritis is slowly progressive disease and causes a chronic knee pain which worsens with activity.
Patient also complains of stiffness after prolonged sitting. Eventually knee deformity may occur.
Rheumatoid arthritis is an inflammatory arthritis which affects multiple joints and knee is commonly included.
There is also associated morning morning stiffness and pain in other joints.
These arthropatheis occur due to deposition of crystals of uric acid (which produces gout) and calcium pyrophosphate (pseudogout) in the knee and other joints
The pain is usually rapid in onset and the knee is markedly inflamed knee joint.
Bursitis is inflammation of naturally occurring bursae in the body. These occur due to acute or chronic trauma or infection.
Description: As a result of trauma, infection, or crystalline deposits, the various bursae of the knee may become inflamed.
Bursitis is well treated with rest and drug treatment.
Bacterial arthritis has an acute presentation. Tubercular and fungal arthritis have subacute or chronic presentation.
Treatment included antibiotics and drainage of pus wherever required.
In patellofemoral syndrome, the patella rubs against the inner or outer femur rather than tracking straight down the middle. As a result, the patellofemoral joint on either the inner or outer side may become inflamed, causing pain that is worse with activity or prolonged sitting.
Progression of the disease leads to softening and decay of the articular cartilage on the undersurface of patella and is called chondromalacia patella.
Tendinopathy of the tendons around the knee causes pain. Various tendinopathies around the knee are
There is insidious onset of anterior knee pain. The problem is common in basketball, volleyball, jumping and running. Pain worsens when person changes position from sitting to standing or when walking or running uphill. There is tenderness at patellar tendon insertion into lower pole of the patella.
This presents with lateral knee pain and there is tenderness in posterolateral joint line. With patient supine, the knee flexed to 90°, and the leg rotated internally, resisted external rotation elicits pain (Webb maneuver). Running downhill is considered as a risk factor.
Iliotibial band is fibrous band that extends from ilium and tensor faciae late to proximal tibia.
Tightness of this band may lead to rubbing against the lateral femoral epicondyle and pain on outer aspect of knee.
This condition commonly affect distance runners.
The pain will typically come on 10-15 minutes into a run and improve with rest.
It is the most common overuse syndrome of the knee and results in lateral knee pain. Cyclists, dancers, long-distance runners, football players, and military recruits are at risk.
Typically, pain begins after completion of a run or several minutes into a run. Pain is aggravated by running down hills, lengthening stride, or sitting for long periods of time with the knee flexed.
The pain is in lateral femoral condyle. Flexing knee while standing with weight on affected knee resulting in pain at approximately 30° of flexion [Renne test]
In Ober test, the patient lies down with the unaffected side down and unaffected hip and knee at a 90° angle. If iliotibial band is tight, the patient will have difficulty adducting the leg beyond midline and may experience pain at the lateral aspect of the knee.
The pain is typically reported at the tibial tuberosity where patella tendon inserts.
The pain is worse when extending the leg. The tuberosity is tender and may become more prominent.
It is a self-limited condition that usually resolves as the bone stops growing with the end of adolescence. Treatment includes rest and NSAIDs.
Diagnosis of Knee Pain
The diagnosis of knee pain is based on presentation of a patient and examination findings. Lab investigations as required are done.
Lab investigations are important to diagnose infection, in inflammatory arthritis etc. The lab work includes complete blood count, ESR estimation, CRP, rheumatoid factor and other parameters as needed.
Fluid from the knee may be aspirated and subjected to Gram staining and culture to look for infective agent, crystals or biochemical analysis.
X-rays can help to detect bony injuries and arthritic changes.
CT scan can identify various bone lesions in greater detail.
MRI is helpful in identification of lesions of soft tissue such as ligament injuries, tendon injuries, cartilage injuries and other soft tissue lesions. tendons, cartilage and muscles.
Diagnostic arthroscopy is a surgical procedure which directly visualizes the lesions like damaged menisci or cartilage.
Treatment of Knee Pain
The treatment of the knee pain depends on the cause.
Minor injuries can be managed at home with over the counter drugs and RICE therapy which stands for Rest, Ice, Compression and Elevation. The injured part should be protected as well [PRICE therapy]
This is very effective treatment for mild sprains. Severe injuries need immediate medical attention.
The dislocation need immediate reduction and immobilization. Fractures need immediate splinting followed by definitive treatment which could be operative or non operative.
Acute ligament injuries require immobilization followed by leg-strengthening exercises.
Cruciate ligament injury may require surgical reconstruction.
Acute traumatic meniscal tear in a young patient would need surgical treatment whereas degenerative meniscal tear can be treated by exercises alone.
Tendon ruptures would require surgical treatment either repair or reconstruction.
Osteoarthritis is treated by NSAIDs, life style modification, weight reduction and exercises. Severley damaged joints may benefit by joint replacement.
Rheumatoid arthritis requires treatment with disease modifying drugs, NSAIDs and life syle modification. Replacement arthroplasty is considered for severely damaged knee joints.
Gout and pseudogout treatment includes control of inflammation with anti-inflammatory medications and drugs aiming at reduction of crystal formation.
Conditions like tendonitis, patellofemoral syndrome and iliotibial band syndrome require treatment with NSAIDs and reduction/modification of activity
Prevention of Knee Pain
Some conditions like acute trauma cannot be prevented.
Risk factors for activity related injury are lack of proper warm up and sudden increase in training severity and duration.
Obesity is a risk factor for osteoarthritis of the knee. Smoking is a risk factor for rheumatoid arthritis.
Weight control reduces the forces placed on the knee during both athletics and everyday walking and may lessen the chance of wear and tear. Muscle strengthening, stretching and judicious exercises reduce the chance of injury during activities.