You are asking about something physicians refer to as the natural history of an injury. In other words, what happens over time? In your case, the question is what is the natural history of an injury to the posterior cruciate ligament (PCL) when treatment is conservative care?
Currently, surgeons are doing more surgeries to restore normal PCL stability but there is insufficient evidence to support this treatment approach. This is especially true when the PCL is the only structure involved (i.e., no other soft tissue injuries are present). There is interest among orthopedic surgeons in knowing if non-surgical treatment for PCL injuries has a higher rate of osteoarthritis later in life. A second question is whether surgery to reconstruct the PCL yields better results (possibly even preventing osteoarthritis).
There are only a handful of long-term studies that might give us some clues but they do offer some interesting information. For example, recent long-term results of nonoperative treatment of PCL injuries were published from the Shelbourne Knee Center in Indiana. The patients were followed a minimum of 10 years after the injury (up to 21 years for some patients).
Everyone in the study had been in a previous study by the same authors. This report is from ongoing follow-up with these same patients who were treated for their isolated PCL injury with a home rehabilitation (exercise) program.
X-rays were used to look for signs of osteoarthritis (e.g., swelling, joint space narrowing, bone spurs). Leg strength, grade (severity) of PCL laxity (looseness), knee range-of-motion, and function were also assessed at each point of follow-up. All measurements were compared with the patient’s other (uninjured) knee.
As it turned out, there wasn’t a higher rate of osteoarthritis (OA) following nonoperative treatment of isolated PCL tears. Patients who had any OA had the same amount from side to side. This suggests that regardless of the PCL injury, they would have developed some (mild to moderate) OA over time. In fact, some of the patients who did have surgery to reconstruct the PCL had worse OA compared with patients who had the conservative care.
The authors concluded that “if PCL reconstruction is being performed to prevent OA, this goal has not been met.” The amount of knee arthritis that develops years after an isolated PCL injury is actually very low. They recommend caution in doing surgery to reconstruct PCL injuries — even when patients are having acute flare-ups of painful symptoms.
Other studies show that whereas PCL surgery can improve knee joint stability, the PCL is not returned to “normal.” Complications of surgery for PCL injuries include knee stiffness, loss of knee motion, infection, and problems with hardware. As the patients in the study just mentioned demonstrated, full knee motion, good muscle strength, and good function can be achieved with a nonoperative approach to this problem. It is also very possible to remain active (even in sports requiring jumping and pivoting) years after the initial injury without surgery.
It might be helpful to know how much arthritis is present in your other knee to compare it to the knee in question. It’s possible that although you have painful symptoms in your previously injured knee, the cause may not be the arthritic changes seen on an X-ray.
Muscle weakness, postural alignment, and/or altered knee proprioception (joint sense of position) could actually be contributing to your symptoms. Likewise, a problem at the hip can be referred to the knee on the same side. A thorough examination may be needed to sort out all the possible causes for your knee pain. A short-term strengthening/rehab program may be all you need at this time.