1
Background
The human menisci are fibrocartilaginous structures that have bony attachments on the tibial plateau. They are connected by ligaments to each other and to the anterior cruciate ligament, the patella, and the femur. These structures are essential for joint stability, shock absorption, distribution of contact forces, and proprioception [ ].
A significant number of athletes present a problem in relation to a symptomatic degenerative meniscus. With relatively poor vascular penetration, of less than one-third of the adult meniscus, healing potential in case of chronic degeneration remains low [ ] ( Fig. 10.1 ).
Meniscal tears can be classified as acute or degenerative. While acute tears are related to excessive forces applied to a normal knee and meniscus, a degenerative tear results from repetitive microtrauma on a worn-down meniscus [ ]. Tears can be described according to their pattern and location. Those located in the avascular zone have a low healing potential spontaneously and after surgical repair [ ]. Degenerative tears generally have a complex pattern and are predominantly found in the posterior horn and midbody of the meniscus [ ].
The patient’s history and physical examination are essential to determine the meniscal origin of pain, particularly with the significant incidence of simultaneous intraarticular injuries.
On physical examination, joint line tenderness, positive McMurray ( Fig. 10.2 ) and Appley grinding tests ( Fig. 10.3 ), and mechanical locking are highly suggestive of a meniscal injury.
Radiographs and magnetic resonance imaging (MRI) are frequently used to diagnose meniscal tears and rule out other sources of microtraumatic knee pain.
A conservative management can relieve pain and improve function of the knee. For patients with persistent symptoms after nonsurgical management, an arthroscopic treatment can provide long term pain relief.
2
Synonyms
Locked knee.
3
Clinical Study
3.1
Symptoms
The main symptom of degenerative meniscal pathology is a mechanical knee pain that can be accompanied by other symptoms.
Athletes suffering from this condition are typically older than 30 years and usually complain of insidious symptoms. No acute trauma is usually found [ ].
Physicians should be attentive to diagnose meniscal injury in patients with knee osteoarthritis (OA) as the two conditions are frequently associated with a concomitant prevalence of 40% [ ].
Typical symptoms associated with knee pain include painful clicking, popping, locking, catching, and giving way.
In some cases, meniscus tears result in decreased walking endurance and balance performance [ ].
3.2
Physical Examination
Physical examination findings that are evocative of meniscus injury include joint line tenderness, positive McMurray’s test, locking, and palpable or audible clicking [ ].
Quadriceps atrophy may be observed a few weeks after injury.
The examiner should evaluate the contralateral knee for comparison.
Unlike acute meniscus injury, overuse meniscus pathology is rarely manifested by joint effusion.
Knee active and passive range of motion (ROM) may be limited because of a physical blocking caused by a meniscal fragment. If the injury is not displaced, active and passive ROM are usually preserved and equivalent to the contralateral knee. With knee mobilization, a clicking may be heard or felt [ ].
3.3
McMurray Test
This test evaluates the medial meniscus. The patient lies supine, the knee is flexed, with the foot and tibia in external rotation. Then the foot and tibia are internally rotated and the knee is slowly extended while rotation is maintained. If pain or a click is felt, the test is considered positive.
3.4
Apley Compression Testor Meniscal Grinding Test
With the patient lying prone, the examiner flexes the knee and applies perpendicular pressure on the sole of the foot toward the examination table. The tibia is then internally and externally rotated. The test is considered positive if pain is felt.
Joint line tenderness on palpation and a positive McMurray test are described as highly suggestive of meniscus injury. Joint line tenderness sensitivity ranges from 63% to 87%, while specificity ranges from 30% to 50%. A positive McMurray test has a 32%–34% sensitivity and 78%–86% specificity [ , ].
It has been advanced that physical examination by an experienced physician has better specificity and positive predictive value than MRI for medial meniscal tears [ ].
4
Differential Diagnosis
Differential diagnosis of degenerative meniscus injuries includes:
4.1
Anterior or Posterior Cruciate Ligament Tears
The patient reports a feeling of instability and ligamentous laxity tests are commonly present on examination.
4.2
Knee Osteoarthritis
Knee swelling, tenderness of the joint line, and limitation of knee ROM are suggestive of knee OA. Standard knee radiographs allow diagnosis confirmation .
4.3
Plica Syndromes
The main symptom of plica syndrome is knee pain localized at the anterior aspect of the knee that is worsened when using the stairs, squatting, or bending and a catching or a locking sensation felt when extending the knee.
4.4
Popliteal Tendinitis
Clinically, this condition is characterized by pain localized at the posterolateral aspect of the knee that appears on weight-bearing activities requiring knee flexion.
4.5
Osteochondritis Dissecans
Patients with osteochondritis dissecans (OCD) typically present with pain and swelling of variable amounts. Pain is generally vague, poorly localized in the knee region and exacerbated by exercise and stair climbing.
4.6
Fat Pad Impingement Syndrome
The patient presents with pain on either side of the patellar tendon, where the fatty tissue sits. The pain may be worse with jumping, prolonged standing, or any other position with knee hyperextension. Also, the area around the patellar tendon may be slightly swollen. Fat pad impingement is not associated with clicking, locking, or instability.
4.7
Inflammatory Arthritis
Prolonged morning stiffness, simultaneous involvement of several joints or tendons, and joint swelling may be a presentation of systemic rheumatologic joint disease.
5
Imaging
5.1
Standard X-rays
A standard radiographic examination of the knee has a limited value in diagnosing degenerative meniscal pathology as the menisci are not visible with this technique. These radiographs are used to investigate for concomitant OA and chondrocalcinosis in older athletes [ ].
5.2
Ultrasound
Ultrasound (US) examination was reported to have low value in diagnosing overuse meniscal injuries. However with the current use of dynamic US, sensitivity in detecting degenerative meniscus has reached 82% based on findings of border irregularity, cystic cavities, and calcification [ ].
It has been reported that the sensitivity, specificity, and accuracy of sonography in the detection of meniscal cysts are 97%, 86%, and 94%, respectively [ ].
On the other hand, US cannot examine deep structures of the knee with high accuracy to rule out other associated causes of knee pain.
5.3
Magnetic Resonance Imaging
MRI is the gold standard for meniscal imaging. This modality has an accuracy of 90%–95% for detecting meniscal injuries [ ].
A normal meniscal structure is well evaluated on T1 sequences, while pathology is best identified on T2 sequences.
MRI signal changes related to meniscal pathology are graded from grade I to grade III [ ].
Grade I signal change is intrasubstance, globular, and does not meet the articular surface.
Grade II signal change is intrasubstance, linear, and does not reach the articular surface.
Grade III changes reach the superior or inferior articular surface, or both, and represent a true tear ( Figs. 10.4 and 10.5 ).
