Keywords: Articular Cartilage Injury, Knee Injury, Knee pain, Physiotherapy, Special tests, Differential Diagnosis, Arthoscopy.
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Clinically Relevant Anatomy
Articular or hyaline cartilage is an extremely smooth, hard material, made up of the protein collagen, which lies on a bone’s articulating surfaces (those surfaces that come into contact with other bones). Its function is to allow for the smooth interaction between two bones in a joint.
Thus, if injured it can lead to impairment in the fluidity of joint movement. In addition articular cartilage is extravascular, meaning that it has no direct blood supply. This means that onceinjured it is extremely slow to heal.
Mechanism of Injury
Damage can occur to the articular cartilage on its own as an isolated condition, or in conjunction with other knee injuries. Anterior cruciate ligament (ACL) injuries are commonly associated with damage to the medial (inner) and lateral (outer) surfaces of the femur (thigh bone) and tibia (shin bone). This is due to the fact that one of the ACL’s functions is to prevent rotation of the knee. In the instance of an ACL tear during a twisting movement, the articulating surfaces of the femur and tibia become damaged.
Other injuries that can lead to articular cartilage damage are those resulting from a forceful impact on the knee joint, such as a tackle in football or rugby. These are commonly associated with injuries to other structures within the joint such as ACL and posterior cruciate ligament (PCL) tears as well as meniscus damage (medial and lateral) and patellar dislocations.
Damage is graded from I-IV and can vary from obvious defects in the bone (grade IV) to very minor microscopic damage (grade I) which will appear normal when looked at with an arthroscopy (visualization of the inside to the knee joint). Injury to the articular cartilage will lead to inflammation and pain in the knee joint and in the long term it is known to accelerate the onset of osteoarthritis. In more severe cases damage to the articular cartilage may also lead to fractures in the bone lying immediately below it- the subchondral bone- a condition known as osteochondritis dissecans
- Recurrent pain and swelling in the knee joint.
- ‘Locking’ of the knee which may be due to loose bodies within the joint
- Knee movements may be associated with audible ‘clunks’ or ‘clicks’.
General Advice for a patient:
- Apply Relative rest, compression and elevation.
- Take paracetamol to control pain.
- See a sports injury specialist.
Health professional and Physiotherapy management:
- Correctly diagnose the injury and extent of the damage – this may require an X-ray or arthroscopy
- Conservative management may involve rest for a number of weeks followed by gentle exercise rehabilitation.
- In more serious incidences in particular those having sustained a fracture (osteochondritis dissecans) surgery may be necessary to fixate the detached fragment
- Other surgery involves attempts to stimulate recovery of the articular cartilage itself such as recruitment of marrow stem cells into the affected area by piercing the subchondral bone.