I dislocated my left kneecap playing tennis on a wet surface. I had arthroscopic surgery to cut the band along the outside of my knee. This was supposed to keep it from pulling the kneecap out of place again. The surgery was done right away, so I thought I’d have a good chance of recovery. Instead, I’ve re-dislocated it three times. Why didn’t the operation work like I thought it would?

It sounds like you had an acute lateral patellar dislocation. This means the kneecap moved off the midline of the knee and ended up along the outside of the knee. When this happens, the medial patellofemoral ligament (MPFL) is usually injured. Studies have shown that half the restraining force holding the kneecap in place comes from the MPFL. Successful treatment must address the condition of the MPFL. If it’s torn and is not repaired, then the chances of recurrent patellar dislocation increase dramatically.

Successful outcomes may depend on the type of surgery performed. Arthroscopic repair reduces the risk of injuring blood vessels and nerves in the knee. And any loose fragments of bone, cartilage, or meniscus can be removed easily.

But complete rupture of the MPFL at its femoral attachment may not be seen and cannot be restored fully by arthroscopic surgery alone. There may be other soft tissue injures that remain unidentified with arthroscopic repair. The surgeon relies on MRIs to help identify the location and extent of soft tissue damage.

You may find out more with an orthopedic re-evaluation. See your surgeon for a follow-up appointment. You’ll be able to find out what factors are involved and what are your treatment options. You may need additional imaging studies with CT scan and/or MRIs to find out for sure what else might be going on that’s hindering your complete recovery.