A recent study from the Human Performance Lab at the University of Calgary in Canada reports a latency (delay) period of 30 years between severe ankle sprain and ankle osteoarthritis (OA).
Younger patients develop arthritis sooner than older adults. Patients with single episodes of ankle sprain also develop OA as much as 10 years before adults with chronic, recurring sprains. The reason for this remains unknown at this time.
It appears that the type of injury and side of the ankle injured have something to do with the development of arthritis later. Lateral ankle sprains along the outside of the leg are more likely to cause malalignment of the ankle and uneven wear on the joint.
The amount of damage at the time of the injury is another factor. Severe ligament tears lead to higher shear forces on the joint cartilage. The result may be damage to the cartilage in addition to the ligament injury.
Without strong ligaments to hold the ankle bones in place, instability occurs. Uneven or excess motion in any direction on either side of the joint comes with an unstable joint. A slow but steady amount of damage to the first layer of joint cartilage later leads to the start of osteoarthritis.