The front of the knee comprises the Knee Cap (Patella) which can be felt as an oval structure when one straightens the leg. The patella sits in a groove (the Trochlea) on the underlying Thigh Bone (Femur) to form the patellofemoral joint. Whilst bending the knee from a straight position the patella moves on the femur maintaining a roughly central position. There are several factors that contribute to this stable movement (tracking)
Soft Tissue Restraints
Malaligned patellofemoral joints present with a patella that lies outside this central position in certain degrees of knee bending. This is a result of imbalanced forces and /or malaligned knees.
Soft Tissue Restraints: Patellas tend to dislocate towards the outer aspect (lateral) of the knee. Tight lateral structures with lax or torn medial (inner side of the knee) structures could contribute to this phenomenon. This could result from an accident whereby an important ligament, the Medial Patellofemoral Ligament (MPFL) is torn. In many cases it is a congenital (the way the person was born) problem. Specialised Physiotherapy Modalities (taping, retinacular stretches, selective muscle strengthening and muscle recruitment education) aim at correcting this imbalance.
Surgical intervention releases the tight lateral structures (Lateral Release) and tightens or reconstructs the lax or torn medial structures (VMO Advancement and MPFL Reconstruction).
Bony Configurations: The convex patella sits in a reciprocal concave trochlea of the femur. A flat patella or trochlea contributes to instability. This is again generally a congenital problem and often found in both knees. Surgical procedures aim at restraining the patella to a central position and/or create a concave troclea (Trochlear Osteotomy).
Alignment: Quite often dislocating patellofemoral joints are a result of congenitally malaligned knees. The patella is a downward continuation of the quadriceps muscle and is attached to the leg bone (tibia) at the tibial tuberosity by means of a tendon (the patellar tendon). If an individual is born with a tuberosity that is significantly lateral (outer side of the knee), the soft tissues (quadriceps and patellar tendon) tend to pull the patella to the outside. Surgery aims at repositioning the tibial tuberosity (Anterior or Anteromedial Tibial Tubercle Transfer) to correct the alignment.
Patients with instability complain of a single or recurrent episodes of the knee cap dislocating and sitting on the outer side of the knee. At times, the dislocation is not complete; there is a mere sensation of the knee "giving away". Left untreated, such knees start paining over years due to articular cartilage changes which develop over areas which are eccentrically and unduly loaded.
A significant number of patients with mild instability problems improve with specialised physiotherapy techniques at our clinic. The secret lies in diagnosing them early and putting them through a well directed rehabilitation programme with possible activity modification.
Frankly dislocating patellas quite often require surgical intervention. This could be purely arthroscopic or arthroscopic assisted surgery by minimally invasive means.
Patients are normally admitted the morning of surgery (fasting overnight) and operated within an hour or two of admission. Surgery typically lasts upto an hour. They wake up in the ward with a bandage around the knee. Patients start exercising the same day and are discharged the next morning after they are comfortable mobilising with support (walker or elbow crutches). Weight bearing and exercises depend on the type of surgery.
Patients with soft tissue procedures are allowed weight bearing earlier than those with bony procedures. Intensive, well directed rehabilitation regimes allow most patients to join sedentary work by two weeks and field jobs by 4-6 weeks. Sports and high demand activities are allowed at approximately 8-10 weeks after surgery.