The cartilage on the surface of the bone can be injured due to trauma or damaged from osteoarthritis. This creates a localized defect in the cartilage which can be painful, and cause the joint to catch with motion and swell.
In 2011, Gobbi et al. published results of 15 patiens who underwent surgery for focal cartilage defects in the knee which included implanting bone marrow derived stem cells in a cartilage matrix to fill the defect. MRI at 2 years showed complete filling of the defect in 12/15 and there was significant improvement in pain and function.
Gobbi et al. (2011) OneStep cartilage repair with bone marrow aspirate concentrated cells and collagen matrix in full thickness knee cartilage lesions: results at 2 year followup. Cartilage (2):286-299