Meniscus is a semi lunar fibrocartilagenous structure in the knee joint between the femoral condyles (thigh bone) and tibial condyles (shin bone). Knee joint has medial meniscus and lateral meniscus. Lateral meniscus is more mobile than medial meniscus. Because of reduced mobility of medial meniscus, there is a high rate of injury when compared to lateral meniscus.
Functions: Meniscus acts as a shock absorber. There is a ground reaction force (GRF), which will exert pressure on our knees when we are standing. As we are walking, running or stair climbing the GRF will increase to 2-3 times of our body Wt. Meniscus reduces the load per unit area on the articular surface and prevents damage to the bony surfaces. Along with the process of aging, the meniscus will also get degenerated and damage articular surface, which leads to arthritis. Total menisectomy results in 50% loss of contact area between the articular bony surfaces. Meniscus transmits the central compressive forces to periphery there by reduces the pressure on articular cartilage.
Mechanism of injury: In young population, meniscus injury can be sports related. Twisting of a semi flexed knee while playing games like football or it can be a motor vehicle accident.
In older adults, it may be due to natural degeneration as explained previously.
Healing of meniscus: There is a critical peripheral blood supply to meniscus. In adults only 6mm or 1/3 rd of the meniscus will receive blood supply, when the age increases it slowly even deteriorated. Tears in vascular portion will be healed but tears extend beyond the Portion will have low healing potential. Tears can be longitudinal, oblique, transverse, horizontal and degenerative. Depend upon the tear the repair can be complicated.
Signs and symptoms: History of pain occurred with twisting injury of the knee joint.
Severe pain with sudden locking of the knee… usually seen in degenerative tears.
Patient may experience a sudden popping or clicking sound in the knee joint.
Investigations: X ray will not reveal any soft tissue injury. MRI will confirm the type of tear.
Special tests: Mcmurry test: knee completely flexed and examiner medially rotates the leg and extends it. If there is, a loose fragment this action will cause a click and pain in lateral meniscus tear and lateral, rotation repeat process will test the medial meniscus. Combination of these tests and clinical signs is needed to have a high level of suspicion in meniscus injury.
Management: Meniscus injuries can be associated with other ligament injuries of the knee. Ex: Medial meniscus, Medial collateral ligament and ACL injury (unhappy triad). Arthroscopic reconstruction of ligaments and meniscal repair is the choice for this type of injuries.
Physical therapy can treat small tears but large tears require surgical management followed by extensive rehabilitation protocol.
Goals of PT: Diminish inflammation and swelling, restore ROM, and reestablish quadriceps activity.
Acute phase: Treatments include cryotherapy, e-stimulation, ultrasound therapy, quadriceps - sets, SLR, AAROM, WT bearing as tolerated, balance and proprioception exercises, light compression wrap.
Advance activity phase: Closed kinetic chain exercises, quadriceps resistance training, sport specific functional progression, advance phase functional training.