What is it ?
During a knee sprain, the patella may dislocate, and may stay unstable afterwards.
Patella pathology
Patella dislocation and instability
Clinical presentation
When the patella first dislocate, the pain is excruciating and the knee is locked in flexion if the patella stays dislocated. The reduction maneuver is simply a knee extension: it will allow the patella to get back in the femoral trochlea. The knee swells up rapidely because of bleeding of the torne MPFL (medio patellofemoral ligament) which is the ligament stabilising the patella. Lipohemarthrosis occurs if severe bone bruise on the patella and the femur. After a first patella dislocation, the risk of patella dislocation is 6 times higher. The following dislocations are much less painful and impressive that the first one.
When to consult a specialist?
A knee specialist should be contacted after a first patella dislocation in order to rule out lesions that should be operated in emergency (as patellar osteochondral fracture); and Xrays and MRI are prescribed. After a second patella dislocation, the knee specialist will prescribe a CT-scan and analyse all the predisposing factors and discuss the pros- and cons- of a patella surgical stabilisation versus a conservative treatment.
Non surgical treatment
The conservative treatment consists of physiotherapy and rehabilitation, and is always indicated after a first patella dislocation, to get back the knee range of motion, to reinforce the muscles which are the patella dynamic stabilisers, and to work on the balance.
Surgical treatment
The surgical treatment can be considered after a second patella dislocation in order to prevent further dislocations and patello-femoral joint wear. The goal of the surgical treatment is to reconstruct the MPFL which is the main static stabiliser of the patella (using a gracilis autograft), and if needed to medialise and/or distalise the patella by doing an anterior tibial tuberosity osteotomy.
Postoperative follow-up
After patella stabilisation surgery, the patient walks with crutches during 4 to 6 weeks, partial weight bearing, and wears a motion brace. Rehabilitation begins the day after surgery.
Risks and complications
The surgical treatment gives good results in terms of patella stability and prevents patella dislocation; the results are less predictable regarding pain: patients who were complaining of patello-femoral pain before surgery may still have some pain after surgery.
The skin incisions may disturb superficial skin sensitivity around the scars, which usually recover with time, or may need ergo therapy sessions.