Our 14-year-old daughter was involved in figure skating. She ended up with an ACL tear that required surgery. Despite our concerns, she went back to practice before she was done with the rehab program. Now the surgeon says the knee is too loose. Is that just a coincidence, or could it be because she disregarded all advice to wait on returning to the ice?

The number of athletes who injure their knees and need anterior cruciate ligament (ACL) repair or reconstruction is on the rise. Every year, almost one-quarter of a million ACL surgeries are performed in the United States. That doesn’t count the number of ACL injuries treated conservatively without surgery.

There are many factors that can affect the success of a reconstructive surgery. Experience of the surgeon, type of graft used to reconstruct the ligament, age of the patient, sex, and compliance with instructions during the post-operative period are just a few. A recent patient study of over 400 ACL surgeries showed that young patients and females are more likely to end up with a lax loose knee joint after ACL reconstruction than older or male patients.

The reasons for this remain a mystery though there are some theories being tested. It is possible that younger patients are less likely to follow the post-operative program as they are instructed. Weaker (less dense) bone and smaller-sized grafts might help explain greater instability among females.

Your daughter falls into the risk category for three factors: younger age, female sex, and failure to follow the postoperative protocol as prescribed. But whether or not those three factors can be directly linked with the laxity now seen in her knee is unclear. The goal now is to complete a strengthening and rehab program that can help prevent any future knee injuries in the presence of joint laxity.