Chapter 20 Knee Pain
Manual of Rheumatology and Outpatient Orthopedic Disorders
Chapter 20 Knee Pain
Norman A. Johanson and Paul Pellicci
Anatomy
Causes of knee pain
Common presenting symptoms associated with knee pain
Physical examination
Diagnostic tests
Principles of treatment
Common causes of knee pain
I. Anatomy
- Joints. There are three articulations in the knee, referred to as compartments. They can be affected separately or together as part of a single process.
- Patellofemoral compartment .
- Medial tibiofemoral compartment.
- Lateral tibiofemoral compartment.
- Ligaments. The knee ligaments are specially designed to accommodate a wide range of motion and flexibility while providing essential stability for weight bearing .
- Medial collateral ligament.
- Lateral collateral ligament.
- Anterior cruciate ligament.
- Posterior cruciate ligament.
- Menisci are crescent-shaped fibrocartilaginous structures that are peripherally situated in the medial and lateral tibiofemoral compartments. They share in weight bearing and augment the stability of the knee.
- Periarticular structures. Several musculotendinous structures pass across the knee to insert at or near the joint. Injury or inflammation of any of these structures can result in knee pain.
- Quadriceps mechanism (quadriceps tendon, patellar tendon).
- Pes anserine tendons (sartorius, gracilis, semitendinosus).
- Semimembranosus.
- Biceps femoris.
- Iliotibial band .
- Popliteus.
- Gastrocnemius (medial and lateral heads).
II. Causes of knee pain
- Traumatic. The mechanism of injury is important in formulating a differential diagnosis; however, components of several mechanisms may be present in a given injury.
- Hyperextension (anterior cruciate tear).
- Varus (lateral collateral ligament tear, anterior cruciate tear).
- Valgus (medial collateral ligament tear, anterior cruciate tear).
- Torsion (meniscal tears).
- Axial impact on femur and posterior displacement of tibia (dashboard injury), patellar fracture, posterior cruciate ligament tear, femoral shaft fracture, fracture dislocation of hip.
- Spontaneous
- Inflammatory (synovitis, tendinitis).
- Vascular disorder (osteonecrosis, sickle cell crisis).
- Degenerative (meniscal tear, articular erosion ).
- Neoplastic (primary or metastatic bone tumors near the knee; soft- tissue tumors around the knee).
- Referred pain from hip or spine disorder.
III. Common presenting symptoms associated with knee pain
- Swelling. Enlargement of the knee with loss of normal contour.
- Locking or severe stiffness (meniscal tear, chondromalacia patellae).
- Giving way or buckling (anterior cruciate tear or patellofemoral disorder).
- Clicking or crackling sound in the knee (meniscal tear or chondromalacia patellae).
- Audible pop at the time of knee injury (cruciate or meniscal tear).
IV. Physical examination
- Observation
- Contour of the knee.
- Alignment of the knee while patient is standing (varus, valgus, flexed, or hyperextended).
- Gait.
- Palpation
- Effusion. Fluid in the knee may be demonstrated by sweeping the hand distally to empty the suprapatellar pouch. Medial and lateral bulging of the capsule can be felt and sometimes seen (distinguish from synovial thickening).
- Popliteal fullness is suggestive of Baker's cyst.
- Joint line tenderness exacerbated by tibial rotation (Steinmann test) is suggestive of meniscal tear.
- Tenderness on patellofemoral compression with the knee slightly flexed is suggestive of chondromalacia patellae.
- Range of motion (active and passive flexion and extension, fixed flexion deformities)
- Note presence of patellofemoral crepitus throughout the range of motion.
- McMurray test. With the knee at first in full flexion, the tibia is rotated internally and externally while the knee is brought slowly into extension. A palpable jumping at the joint line sometimes accompanied by an audible click is suggestive of a meniscal tear.
- Strength
- Thigh circumferences are measured and compared (10 cm above patella).
- Quadriceps strength. Note whether an apparent weakness is secondary to pain, stiffness, or actual muscle dysfunction. Note the presence of thigh atrophy.
- Hamstring strength.
- Stability
- Varus and valgus stability is best demonstrated by cradling the knee with one hand and, with the knee in extension, applying a medial or lateral knee stress. Any more than a jog of motion is suggestive of medial or lateral collateral ligament laxity.
- The anterior and posterior cruciate ligaments are tested with the knee in flexion and extension. While sitting on the patient's foot with the knee flexed to 90 degrees, the examiner applies anterior and posterior displacement force on the proximal tibia. A firm end point should be present in each direction (anterior drawer test). With the knee in extension, the tibia is lifted anteriorly on the femur (Lachman test). Minimal excursion and a firm end point should be noted.
V. Diagnostic tests
- Radiography should be performed while the patient is standing (anteroposterior and lateral views) to demonstrate joint space narrowing. Tangential patellar views (Merchant views) are obtained to assess the patellofemoral compartment. A tunnel view is obtained to assess the contour of the intercondylar notch .
- Screening blood tests such as complete blood cell count and measurement of differential, erythrocyte sedimentation rate, biochemistry profile, and rheumatoid factor should be performed if systemic disease is suspected.
- Aspiration of synovial fluid for analysis of cells and crystals is helpful in rheumatoid arthritis, gout, and pseudogout. Culture and sensitivity are definitive in infectious arthritis.
- Arthrogram is helpful to confirm meniscal and cruciate tears and to demonstrate a popliteal cyst or nodular synovitis. This test has generally been supplanted by the MRI.
- Bone scan is helpful in demonstrating early osteonecrosis (increased or decreased uptake in subchondral bone) when radiographic findings are still normal or when there is the presence of a stress fracture. It can also define the diffuse increased uptake in RA or medial uptake in OA.
- Magnetic resonance imaging (MRI) has become the imaging procedure of choice for evaluating torn menisci and ligaments.
VI. Principles of treatment
- Acute phase
- Rest through decreased activity and weight bearing (crutches, cane if needed).
- Antiinflammatory medications.
- Therapeutic aspiration of synovial fluid (or blood in traumatic effusion) often relieves pain. This can be supplemented by injection of a local anesthetic into the joint.
- Injection of a steroid preparation into the knee is recommended for older patients with arthritic changes on radiography or in patients with inflammatory joint disease in whom infection is not present.
- Convalescent phase
- Quadriceps and hamstring exercises are frequently used for many knee disorders. Straight leg raising without weights is helpful in arthritis patients because it minimizes patellofemoral stress. Exercises with weights are more effective in rehabilitation after athletic injuries.
- Progressive activities (e.g., swimming and bicycle riding ) preserve knee motion and strength without excessive impact loading.
- Braces are used according to the condition being treated (usually not effective in arthritis, but beneficial in chondromalacia patellae and mild ligament injuries).
VII. Common causes of knee pain
- Chondromalacia patellae is a spectrum of knee disorders resulting from excessive pressure on the patellar cartilage and the subsequent softening and fibrillation of the articular surface. Increased pressure may be caused by an abnormality of patellar tracking during knee motion. Associated conditions include femoral anteversion, external tibial torsion, valgus knee alignment, a hypoplastic high-riding patella, or foot pronation. Excessive malalignment may cause subluxation or dislocation of the patella.
- History
- Anterior knee pain is felt during climbing or descending stairs, sitting for long periods of time, or squatting.
- There may be a history of direct trauma to the patella (dashboard injury).
- Sports that may cause overloading of the patellofemoral joint (jogging, basketball , gymnastics, dancing ) are associated with chondromalacia.
- Physical examination
- Mild peripatellar swelling may be present, but joint effusion is rare.
- Crepitus of the patellofemoral joint is usually palpable during range of motion. Full flexion may elicit an increase in pain.
- In cases of patellar malalignment or recurrent subluxation/dislocation, the patella may exhibit mediolateral hypermobility, and when the patella is displaced laterally, significant apprehension may be elicited.
- Radiographic findings
- Tangential view of the patella (Merchant view) may demonstrate lateral displacement or tilt of the patella. Narrowing of the joint space is suggestive of patellofemoral arthritis.
- Lateral view of the knee may demonstrate a high-riding patella (patella alta), which has been associated with patellofemoral pain. Patella alta is defined as a ratio of the length of the patellar tendon to the length of the patella greater than 1.2:1.0.
- Differential diagnosis. Chondromalacia patellae must be distinguished from meniscal tears. Meniscal tears are more frequently associated with a specific traumatic event and even more likely to result in a knee effusion, locking, and a reduction of range of knee motion. Meniscal tears may be ruled out by an arthrogram, MRI, or arthroscopic evaluation.
- Treatment
- Temporarily discontinue or reduce those activities that exacerbate pain.
- Quadriceps muscle strengthening is the most important objective. This is accomplished through quadriceps exercises in the range of 90 to 30 degrees or through straight leg raising.
- In some cases, nonsteroidal antiinflammatory medications are necessary to control acute pain in chondromalacia. Ibuprofen in a dosage of 600 mg four times daily may be effective.
- Meniscal tears. Traumatic tears of the medial and lateral menisci are common causes of knee pain, particularly in athletic persons. The medial meniscus is by far the most frequently affected.
- History
- A twisting injury is often the cause of a meniscal tear.
- Swelling of varying severity is often reported .
- Knee stiffness, pain, and limitation of motion are frequent complaints. A history of locking is less common.
- Physical examination
- Swelling and knee effusion are frequently present.
- Tenderness is present along the medial or lateral joint line.
- Range of motion may be limited in extension and flexion, or the knee may be locked in one position.
- Result of the McMurray test or Steinmann test (tibial rotation) is often positive with meniscal tears.
- Diagnostic studies
- Radiographic findings in the knee are usually normal except for the demonstration of a knee effusion.
- Arthrography or MRI will demonstrate meniscal tears in most cases.
- Arthroscopy is an important therapeutic modality for meniscal tears.
- Differential diagnosis
- Medial collateral ligament sprains may produce medial joint line pain and tenderness with a limp and an effusion. Locking is not present. Arthrography is negative or demonstrates leakage of dye in the area of the ligament injury. MRI is diagnostic.
- Acute chondromalacia patellae may produce anteromedial pain. An effusion is rarely present, and locking is also very uncommon. Findings on arthrogram or MRI are negative.
- A pes anserine bursitis presents with pain and tenderness over the proximal medial tibia just below the joint line without effusion, limitation of motion, or locking. Direct tenderness is present over the bursa, and the arthrographic or MRI findings are negative.
- Medial compartment tibiofemoral osteoarthritis may produce an effusion with medial joint line pain, tenderness, and a limp. Radiography will demonstrate sclerosis and joint space narrowing in the medial aspect of the knee joint.
- Treatment. In patients with a locked knee or recurrent symptoms from a torn medial meniscus, surgical removal is the treatment of choice. If the tear is longitudinal, simple excision of the injured segment may be performed. Arthroscopic techniques are the preferred method of treatment.
- Tibial tubercle apophysitis (Osgood-Schlatter disease) occurs primarily in adolescents and presents as pain located at the insertion of the patellar tendon into the tibial tubercle. Some investigators believe the syndrome represents an injury to the apophysis that is similar to mild avulsion.
- Physical examination. There is localized pain on palpation of the tubercle.
- Radiography often shows a displaced ossicle of bone anterior to the tubercle within the tendinous insertion.
- Treatment. The pain usually disappears when the ossicle fuses to the underlying tibia. Until that time, the patient's activity level must be monitored . Depending on the severity of the pain, some or all athletic activity must be discontinued. A cylinder cast for 4 to 6 weeks may be necessary in resistant cases. Ibuprofen 600 mg three times per day or other NSAIDs may be used during the acute phase.
Books@Ovid
Copyright 2000 by Lippincott Williams & Wilkins
Stephen A. Paget, M.D., Allan Gibofsky, M.D., J.D. and John F. Beary, III, M.D.
Manual of Rheumatology and Outpatient Orthopedic Disorders
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