The Hypertrophied Patella – Does it really exist?

The Knee joint reveals its mysteries far more often than expected. So often a simple case of fracture patella with a Tension Band Wiring (TBW) turns out to be a nightmare for the Physiotherapy management.

The fracture of the patella is one of the commonest conditions that a Physiotherapist encounters during the clinical practice. The patella (knee cap) is a sesamoid bone, i.e. it is a bone in between the tendon of the quadriceps muscle and is a cancellous (porous) type of a bone. Although the patella is within the tendon of the quadriceps, it does not separate the quadriceps tendon, but infact it is embedded within the extensor retinaculum of the quadriceps. The patella acts as a pulley to increase the moment arm of the knee joint and increases the efficacy of the quadriceps muscle to bring about extension of the knee joint. This is such a beautiful bio-mechanical mechanism which is really unique in the human body.

The quadriceps group of muscles are made of 4 different muscles, viz the single joint (uni-articular) 3 Vastii (Vastus Lateralis, Vastus Intermidius and Vastus Medialis) which are phasic, red muscles responsible for the knee joint anterior compartment dynamic stability and the two joint (bi-articular) Rectus Femoris which is flexor of the hip and extensor of the knee joint and is a tonic, white muscle responsible for force production and torque generation of the knee joint during extension in open and closed chain activities.

The patella works as a pulley glided by the shape of the articular surface of the femoral condyles. It has the capability to move medial to lateral, superior to inferior and rotate inwards and outwards within the articular capsule of the knee complex. This variation in movement allows the patella to move and align itself in relation to the different fibres of the vastii and rectus to bring about an efficient extension of the knee. It is generally assumed that during extension of the knee from 120 – 0 degrees, the patella aligns the fibres of the vastus lateralis fibres in 120 – 80, vastus intermidius aligned during 80-40 and vastus medialis aligned during 40 – 0 degrees of the extension. Thus the patella plays an extremely crucial role in knee extension, not by merely increasing the knee joint moment arm, but also by aligning the fibers of the quadriceps. The rectus femoris is responsible for force generation for the knee movements and is extremely crucial for activities like walking, running, kicking (a ball) etc.

Flexion of the knee is brought about by the bi-articular (2 joint) hamstrings group of muscles which constitutes of the semi-tendinosis, semi-membranosis and the biceps femoris. During flexion of the knee from 0-120 degrees, the patella undergoes a tracking movement in the inferior (downward) direction. It carefully moves within the space of the femoral condyles within its lower articular surface after around 90 degrees of knee flexion and thus reduces the tension generation in the capsule of the knee joint.

This mechanism and function of the knee is severely hampered when the patella is fractured. Although the patella is not a weight bearing bone during normal bipedal ambulation, its fracture completely disrupts the extensor mechanism of the knee making this entire system collapse. Newer line of orthopaedic surgical management offers wonders in management of the patellar fractures. The tension band wiring fixation with ‘Krichners’ wire fixation seems to be the most commonest and most reasonable line of management for patellar fractures wherein the distraction pull by the quadriceps (and the ligamentum patellae in the other direction) is converted into compression forces by the TBW thereby accelerating the early healing the restoration of the function of the extensor mechanism.

But the patella, which is a porous bone, bleeds during the course of the trauma leading to its fracture. This bleed gets confined along with patellar fracture within the extensor retinaculum and as the patella gets healed and calcified, can also get calcified. Although this is not very evident in the radiograph (X-Ray), it can still be visualised on careful observation, mainly after 4-6 weeks post fracture. But it is best evident to the clinician by palpating the patella which seems to be big and enlarged (comparison with the opposite knee is extremely useful for confirmation). This enlarged size of the patella is poorly studied in literature and thus have been coined as a “Hypertrophied Patella” by me. Although the term hypertrophy is associated and used with muscles in relation with an increase in their size and cross sectional area, it seemed appropriate to use this term for the patella in this condition also (although not an absolutely scientific term). The term “Hypertrophy of the Patella” has been used in literature by Cave (1950) and Linthoudt (2008), it has been in relation to the multiple epiphyseal dysplasia, not the adult patella per se.

The patella, which seems to be enlarged on palpation, does not function appropriately in regards to its flexion function of the knee. It is extremely difficult for the patella to move within the femoral condyles after 90 degrees of knee flexion and thus starts becoming a nightmare for the Physio to obtain a full range of the knee. Clinically, this state of the knee may not affect the extensor mechanism of the knee joint and thus, the bio-mechanical functions of the quadriceps tend to remain intact. But in few of the cases, a dysfunction in the extension mechanism has been found, primarily due to the reduced mobility of the patella. The swelling around the patella is not easily and readily manageable and as it tends to consolidate, it reduces the mobility of the patella in all the directions. This prevents the patella from being aligned to the respective fibers of the quadriceps and leads to loss of efficiency of the knee extensors. It can also lead to compression of the patella against the articular surfaces of the femur (specially the medial condyle of the femur) leading to early degeneration of the articular cartilage of the patella as a complication in the near future. Thus controlling the swelling (oedema) and restoring a normal patellar mobility becomes a priority in the early management of patellar fracture rehabilitation.

The goal for Physiotherapy management in a case of fracture patella includes:

1. Pain management

2. Controlling the swelling

3. Increasing the range of motion of the knee joint

4. Increasing the strength of the extensor mechanism

5. Increasing the strength of knee flexors

6. Early weight bearing and ambulation

7. Functional restoration

1. Pain management:

This can be obtained by Cryotherapy (or heat if swelling is not an issue), and by low velocity oscillations for knee and patella

2. Controlling the swelling:

Cryotherapy, compressions, knee brace (if required)

3. Increasing the range of motion of the knee joint:

This is the most crucial challenge. The patient cribs and curses every morning due to their inability to squat. Patellar mobilisation and quadriceps MFR helps in gaining early knee range till 90 degrees. But range beyond this is very difficult to obtain and may take as long as 6 months to be achieved. Being too impulsive and over-enthusiastic in this situation may prove to be too dangerous as repeated application of force and pressure (passively or by CPM machine etc) may cause over lengthening of the ligamentum patellae due to collagen distraction and may produce loss of efficiency of the extensor mechanism. The therapist may perceive a progressive weakness in the quadriceps strength in 4-6 weeks, not realising that the overstretching has led to dysfunction of knee extensors and loss of efficiency of force production at the tibia. This, unfortunately, cannot be reversed by any amount of strengthening of the quadriceps and thus has to be prevented at all costs.

4. Increasing the strength of the extensor mechanism and Knee flexors:

Open chain exercises till 4 weeks and later combination of open and closed kinematic chain exercises is very useful for gaining the strength of the knee muscles. Care should be taken to improve on the Endurance of the Vastii (by RPE) and the strength of the Rectus femoris and Hamstrings (by 1 RM and PRE), as per their functional needs. Also to understand the various angles that the vastii function and thus multiple angle, short arc training can be more beneficial rather than full range movements.

5. Early weight bearing and ambulation:

There is no contraindication for early weight bearing and gait training in these cases. Always, a good rapport and communication with the operating Orthopaedic Surgeon turns out to be a blessing. Full weight bearing, as early as in 4 weeks, can be obtained. Gait training is extremely crucial as the reduced patellar function affects the loading response, mid stance, pre swing and swing phases of Gait and can result in a Stiff Knee gait pattern. Pain is rarely a hindrance in Gait training.

6. Functional restoration:

Activities such as sitting on low surfaces, squatting, cross leg sitting etc, requiring more than 90 degrees of knee flexion may be very difficult to obtain for almost 4-6 months. But walking, stairs, riding etc is not much of a hassle. Always maintain good communication with the patient and surgeon and have clarity of thoughts in regards to the Physiotherapeutic management.

Thus, the patellar fracture turns out to be a simple, but challenging aspect in PT rehab. The knee gains a good range and function in the near future due to reabsorption of the excess calcification with a progressive aligned and directed force of the quadriceps and is not a matter of worry at all. (Although is a time consuming process). Although not much documented, the “Hypertrophied Patella” does seem to exist and also requires a better understanding of the knee joint and is a challenge worth accepting.

Dr. Apurv Shimpi (Community Physiotherapist)

1. Cave EF, Rowe CR. The Patella, Its Importance in Derangement of the Knee. J Bone Joint Surg Am, 1950 Jul; 32 (3): 542 -566 

2. Van Linthoudt D. Patellar hypertrophy: rare abnormality associated with a multiple epiphyseal dysplasia. Praxis (Bern 1994). 2008 Aug 13;97(16):893-7. French.

3. Gosal HS, Singh P, Field RE. Clinical experience of patellar fracture fixation using metal wire or non-absorbable polyester — a study of 37 cases. Injury, Int. J. Care Injured 32 (2001) 129–135

4. Hoshino MC,  Tran W, Tiberi JV, Black MH, Li BH,  Gold SM,  Navarro RA. Complications Following Tension-Band Fixation of Patellar Fractures with Cannulated Screws Compared with Kirschner Wires. J Bone Joint Surg Am April 2013; :653-659.

5. Baran O, Metin Manisali M, Berivan Cecen B. Anatomical and biomechanical evaluation of the tension band technique in patellar fractures. International Orthopaedics. August 2009, 33(4): 1113-1117

6. Cramer KE, Moed BR. Patellar Fractures: Contemporary Approach to Treatment. J Am Acad Orthop Surg November 1997; 5:323-331.