→ damage to the knee’s lining cartilage.
Knees contain two kinds of cartilage for support and mobility: meniscal and chondral (or articular). Chondral cartilage is a thin, smooth material that covers the ends of the thighbone and shinbone (the femur and tibia). It reduces friction as the bones glide against each other during movement of the knee.
Chondral injuries can happen in several ways. The cartilage can be damaged when the knee pivots or twists suddenly – for example during sport, or by a direct blow to the knee. For this reason a chondral injury is often accompanied by another condition, such as an ACL injury. Since there is no direct blood supply to the chondral cartilage, it is very slow to heal after injury. Wear and tear is another cause of chondral damage, particularly in older people. It might come about after a series of minor injuries over a long period of time, or with the onset of osteoarthritis. Chondral damage varies in degree, from slight swelling to a complete wearing-away of the cartilage where the underlying bone is exposed.
A chondral injury is often less obvious than a meniscal tear or an ACL injury. There will usually be immediate pain on impact, but swelling may be the only serious symptom thereafter, possibly delayed until several hours after the injury, or occurring intermittently over the coming days and weeks. Depending on the severity of the damage, patients may experience pain after prolonged walking, or on climbing stairs. Sometimes pieces of cartilage can break away from the bone and catch in the joint, causing it to ‘lock’ and making it difficult or impossible to fully extend the knee. The damage may also be accompanied by a grinding noise (crepitus).
Chondral damage can be difficult to diagnose, since it may not be accompanied by visible swelling. If this is the case, we may need to arrange for an x-ray or MRI scan; a narrowing of space between the bones can indicate that there has been cartilage loss in the joint. If the diagnosis is still inconclusive, we may recommend keyhole surgery so that we can take a closer look.
Conservative treatments for chondral injuries range from painkillers and injections to physiotherapy, in particular to strengthen muscles around the joint. More severe injuries may require operative treatment. Some of the surgical procedures used to tackle chondral damage include: microfracture (where tiny fractures are created inside the bone to encourage new cartilage development), debridement (shaving back shredded cartilage to reduce abrasion) and mosaicplasty (transplanting small grafts of bone and cartilage to provide a new surface where lining has been lost).