Patellar tendinitis represents a spectrum of tendon damage ranging from acute inflammation, through chronic inflammation, to a gelatinous degeneration of the tendon tissue known as 'mucoid degeneration'. A person with patellar tendinitis may exhibit components of each of these as their condition evolves.
Mucoid degeneration is a 'burned-out' situation where longstanding tendon inflammation results in loss of structural integrity of the tendon with the healthy tissue becoming replaced with a gelatinous or mucoid substance. Despite this degeneration of tissue, the surrounding area can remodel.
Patellar tendinitis is common and I have suffered a fair bit myself with this condition over the years and have first-hand experience of it.
As explained in a previous section, it is important to assess the contributory factors, such as training regimes and lower limb biomechanics, addressing any problems and allowing a reasonable period of relative rest while arranging investigations to fully establish the diagnosis and decide on management.
Ultrasound is the mainstay of investigation and one should be able to identify with ultrasound any areas of inflammation and mucoid degeneration, as well as any inflammation of the paratenon (the loose sheath around the tendon that provides its nutrition).
First line management
Physiotherapy remains the first line of treatment - in the form of eccentric strengthening, such as single leg knee drops (eg squatting down on one leg and controlling it a lot) - but physiotherapy is challenging with a narrow therapeutic window.
Acute inflammation will usually respond to activity modification and a regime of eccentric exercises, with follow-up by the doctor after 2 to 3 weeks. If the patient is still struggling, then steroid injections might be considered.
However, the role of steroid injections is debatable, and its role should be limited to calming aggressive inflammation to allow the physiotherapy to proceed smoothly. Steroid injection needs to be into the paratenon, not the tendon itself - a challenging procedure which should be done under ultrasound guidance or by a skilled clinician.
PRP (platelet-rich-plasma) injections have been shown in large metastudies to be of no benefit for patellar tendinitis.
Second line management
If physiotherapy is ineffective, then one can progress to shockwave therapy, which has been shown to be quite promising although it also takes a while to have real effect - from four to six months. Unfortunately shockwave was not around at the time of my own patellar tendinitis, but my problem settled with eccentric strengthening although it took three months. An eccentric exercise regime should continue together with the shockwave therapy.
Shockwave works by stimulating the proinflammatory state (releasing specific chemicals and cells that appear before actual inflammation), so it will be ineffective if one is simultaneously taking NSAIDS (non-steroidal anti-inflammatories) or if steroid injections have been given within the previous two weeks, as both of these will suppress proinflammation. A standard regime would be three shockwave treatments of 10 minutes per session, with each session a week apart. The patient my be a bit uncomfortable for a day or two after a treatment session, but patients often say that it feels good despite the discomfort as it feels like a tough workout rather than frank pain.
Improvement is indicated by a decrease in the patellar tendon pain, and improement can continue for up to a year. I often repeat the ultrasound at three months to assess progress and to see if things are looking better.
Third line management
If patients are not responding to first-line or second-line management, it may be necessary to progress to surgery, which can be performed arthroscopically (through a keyhole incision) or open (cutting the area open), depending on the extent of mucoid degeneration. If there is a lot of mucoid degeneration I usually choose to open the area as it can take a long time to clean out the degenerative tissue via an arthroscope. In both cases, before I start the surgery, I put the patient's knee into 90 degrees of flexion and localise the painful region, marking it with a pen. Then when the patient is asleep, I needle the area to localise the region where I will debride with the shaver (if the procedure is arthroscopic) or down to which I will incise (if the procedure is open). Then I go in and carefully remove the gelatinous mucoid material.
Usually this is a day-case procedure, and the patient will go home the same day. After discharge the patient will start four to six weeks of gentle ROM (range of movement) exercises and stretches, and then progress to eccentric exercises.